Search

The extrusion procedure used to manufacture Short Fiber Reinforced Composites (SFRCs) results in significant anisotropy in the components due to the skin‐core structure. While there are existing accurate stiffness prediction methods available, there is still a need in engineering for an efficient and cost‐effective prediction method. This work proposes an efficient, low‐cost and effective stiffness prediction method for skin‐core structure using the orientation averaging method and series–parallel model. Initially, the sample is analyzed using industrial CT and metallographic microscopy to ascertain the fiber characteristics and skin‐core dimensions. Furthermore, it is presumed that the skin and core are distinct materials and their stiffness is determined using the orientation averaging method. Finally, the stiffness of the sample is determined by employing a series–parallel model for analyzing stress–strain transmission, which involved merging the skin and core components. Experimental and finite element results confirm the method's accuracy, boasting a calculation time of 31.36 s and a maximum stiffness error below 10%. This method is expected to be applied to automotive, construction and other engineering fields to meet the demand for fast, cost‐efficient and effective stiffness prediction of SFRCs. Highlights: A stiffness prediction method is proposed, which is no modeling required.Combined with Hashin‐Tsai, orientation average method and series–parallel model.The stiffness of skin‐core structure is predicted by this method within 31.36 s.This method can be extended to more complex fiber orientation examples. [ABSTRACT FROM AUTHOR]

Highlights The extensive use of multidirectional composite laminates requires to understand the delamination behavior at interfaces between plies with different fiber orientations. In this study, double cantilever beam testing was performed to investigate the mode I interlaminar fracture of carbon fiber reinforced polymer laminates with different central interfaces (0//0, 0//+45 and +45//−45). X‐ray microtomography revealed the curved crack front shape that was incorporated to calculate fracture toughness. The fracture toughness varies with the crack length in a typical delamination resistance curve, which can be quantified by an empirical equation. Incorporation of variable fracture toughness into a cohesive zone model can better predict the delamination fracture of the laminate, compared to constant toughness. It was found that the delamination mechanism is independent of central interfaces. However, compared to unidirectional laminates, multidirectional laminates are less resistant to crack initiation, but more resistant to propagation with higher toughness and shorter fiber bridging zone. Mode I interlaminar fracture of CFRP laminates with different central interfaces was investigated experimentally and numerically. Curved crack front shape was incorporated to calculate fracture toughness. Incorporation of variable fracture toughness into a cohesive zone model can better predict the delamination fracture of the laminate. Multidirectional laminates are less resistant to crack initiation but more resistant to propagation with higher toughness and shorter fiber bridging zone. [ABSTRACT FROM AUTHOR]

Grinding could be used to enhance accuracy and quality of carbon fiber‐reinforced poly‐ether‐ether‐ketone (CF/PEEK) composites. However, the grinding mode, namely up‐grinding (UG) or down‐grinding (DG), is usually neglected while unbefitting grinding mode choice may cause inferior surface quality. To investigate effects of grinding modes on grinding performance of anisotropic CF/PEEK, grinding experiments in UG and DG were carried out under different fiber orientation angles θ. Experimental results indicated that maximum grinding temperatures and normal grinding forces in UG were lower than DG regardless of the abrasive grit sizes. Material removal mechanisms of CF/PEEK affected by grinding mode were revealed by analyzing morphologies of surface, chip and grinding wheel. When θ = 0°, the dominant mechanisms in DG were extrusion fracture and fiber deformation, while they were interface shear debonding and bending fracture in UG. When θ = 90°, the dominant mechanisms in DG included interface layer separation and bending fracture, while they were shear and extrusion fracture of well‐supported fibers in UG. Thus, UG was more favorable for material removal, obtaining lower surface roughness values, fewer machining defects and less wheel wear than DG. This study will provide technical guidance for high‐quality grinding of carbon fiber‐reinforced thermoplastic composites. Highlights: The effects of grinding modes (DG and UG) on the grinding performance of anisotropic CF/PEEK composites were investigated.Material removal mechanisms of CF/PEEK affected by grinding mode were revealed under different fiber orientation angles.The maximum grinding temperatures and normal grinding forces in UG were lower than DG.UG was more favorable for material removal in grinding, and could produce better ground surface quality than DG. [ABSTRACT FROM AUTHOR]

Highlights An image‐based fiber orientation analysis technique has been employed to study the effect of initial charge coverage and preferential fiber alignment on the flow‐induced fiber orientations in carbon fiber sheet molding compounds (SMCs). The initial charge coverage area exhibited minimal fiber reorientation while significant fiber alignment in the flow direction was observed in the regions of greatest flow. Novel subsurface analysis using the same full‐field orientation analysis technique also showed the presence of a skin‐core structure with greater flow‐induced fiber alignment at the mold surfaces, while the core retained more of the initial fiber orientation distribution. Edge effects were also revealed by this analysis at the mold walls. Tensile testing from two orthogonal directions showed that panels molded from lower charge coverage resulted in better mechanical performance and lower anisotropy. Moreover, by encouraging charge flow in the preform's preferential alignment direction, high tensile stiffness and strength in the preferred direction were achieved (56.7 GPa and 238.9 MPa, respectively) at 30% fiber volume fraction. This provides a practical demonstration of the value in controlling fiber orientation, with respect to charge positioning and mold flow, to maximize and tailor the composite performance of SMCs typically used for automotive applications. Low‐cost scanning technique is extended to assess internal fiber orientations Full‐field orientations are measured before and after molding Investigation of how charge size and shape can affect orientations Combining effects of flow and initial orientation to tailor SMC performance Circular statistics provides a thorough analysis of orientation distributions [ABSTRACT FROM AUTHOR]

The main objective of the present study is to implement a functionally graded materials (FGM) technique to reduce the hole effect in fiber reinforcement polymers. The tensile and fracture behaviors of conventional and FGM composites containing open holes have been investigated. Open‐hole specimens having different hole sizes have been fabricated using a hand lay‐up technique with different cross‐ply stacking sequences and various numbers of layers to study the open‐hole effect on their tensile strength. On the other hand, a three‐dimensional finite element analysis with the Hashin model was implemented to observe the failure modes along each layer. Experimental and numerical data revealed that the FGM technique enhanced the performance of specimens in the presence of a hole by increasing the fibers around the hole area. Furthermore, the [0°/90°/0°] sequence has more tensile strength than [0°/90°]s and [0°/90°/0°/90°/0°] sequences. It can be concluded that the bearing capacity of cross‐ply laminates is proportionally dependent on the ratio of the number of 0° layers to the number of 90° layers and inversely dependent on the specimen thickness. Highlights: Dense fibers around the open hole improve its strength in laminated composite.The FGM concept has been successfully employed to improve open‐hole strength.The stacking sequence [0°/90°/0°] has better tensile strength than [0°/90°]s.FEA has successfully simulated the FGM concept around the open hole.The open‐hole failure occurred in the same direction as fiber orientation. [ABSTRACT FROM AUTHOR]

This study investigates the hygrothermal aging effect on the tensile and impact behavior of flax/PLA biocomposites. Specimens underwent up to four weeks of conditioning at 40°C in a climate chamber with water. Analysis covered porosity, moisture diffusibility, and transversal microstructure, enabling assessment of tensile strength, tensile modulus, and impact performance in relation to moisture uptake and fiber orientation. The study of tensile properties revealed that at approximately 12% moisture content, stiffness and yield stress decrease, while strength remains constant. Moisture diffusivity is higher in warp and weft yarn directions than the out‐of‐plane direction. Tensile testing at environmental equilibrium moisture reveals greater stiffness in the weft direction, correlated with lower crimp percentage and yarn angle. The main contribution of the paper is the study of the influence of moisture on the impact behavior, the results show that energy absorption capability of flax/PLA biocomposite increases with moisture content. Highlights: Fully biodegradable composite material by heat‐compression molding subjected to hygrothermal aging conditions for up to four weeks.The moisture diffusivity in both the warp and weft yarn directions registered higher values in comparison to the out‐of‐plane direction.Tensile testing at environmental equilibrium moisture revealed that the stiffness in the weft direction presented higher values.At 12% of moisture uptake, the stiffness and yield stress reached their lowest values, while strength remained constant.However, the low‐velocity impact properties of the composites exhibited improvement with moisture. [ABSTRACT FROM AUTHOR]

Highlights Additive manufacturing has enhanced the production of complex parts with greater efficiency. However, inherent drawbacks such as reduced mechanical properties still pose challenges, necessitating further improvements to bridge the gap and meet industry demands. Therefore, this study investigated the use of glass fiber woven fabric with vat‐photopolymerization printing to achieve composite parts with superior mechanical properties. This approach offered an advantage in reducing the production time required for fiber‐reinforced composites by eliminating the need for curing processes or vacuum infusion. The mechanical properties of the composite panels manufactured with this method were investigated using flexural, interlaminar shear (ILSS), impact tests with different fiber orientations, and fiber volume fractions. The results of the mechanical tests showed maximum flexural strength of 295 MPa, impact strength of 174 kJ/m2, and ILSS of 20.58 MPa. In addition, optical images were taken to examine the cross‐section of the printed parts, which revealed a uniform and good wetting of the fibers. The findings suggest that glass fiber woven fabric in vat printing is a promising approach for producing composite parts with enhanced mechanical properties and reduced production rate. Additive manufacturing of glass fiber woven fabric reinforced with VPP printing. Reduced production time and microstructure by using layer‐by‐layer manufacturing. Maximum flexural strength: 295 MPa, impact strength: 174 kJ/m2, ILSS: 20.58 MPa. Consistent porosity values with the increasing number of layers. Promising for producing standard and thick composites with improved properties. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) composites with chopped strand mat (CSM) and woven roving mat (WRM) reinforcements are widely used in high‐pressure piping due to their favorable strength‐to‐weight ratio. However, cyclic loading from vibrations and pulsating forces can induce internal microstructural damage, ultimately leading to performance degradation. A thorough understanding of this damage mechanism is imperative for its mitigation, necessitating a detailed examination. The present study aims to investigate the fatigue response and damage mechanisms in CSM and WRM composites subjected to tension‐tension cyclic loading. Scanning electron microscopy analysis of edge sections revealed the development of perpendicular microcracks in both composites. CSM composites exhibited fatigue cracks parallel to the loading direction and higher levels of parallel interface debonding compared to perpendicular matrix cracks. Finite element analysis of the representative volume element revealed the role of shear stress in the matrix in initiating parallel cracks, thereby explaining the damage initiation mechanism in CSM. These findings highlight the distinct damage mechanisms arising from the differing fiber arrangements in CSM and WRM composites, providing valuable insights for optimizing their performance under cyclic loading conditions. Highlights: Fatigue response of CSM and WRM was influenced by fiber orientation and weaving pattern.Perpendicular fibers were the most probable fibers to have their interface form a crack.Fatigue cracks parallel to the direction of loading were observed in CSM composites.Quantified the true 3D internal microstructural damages for the first time. [ABSTRACT FROM AUTHOR]

In this article, the axial crushing behavior of CoFeSiB amorphous alloy fiber reinforced epoxy composites (AAFRCs) with different fiber volume fractions (30%, 40%, 50%, and 60%), fiber orientations (0°, 15°, and 30°), and fiber shapes (straight and sinusoidal) were investigated under compression condition. The results show that energy absorption (EA) and crush force efficiency (CFE) of the composites show a tendency to increase and then decrease with the increase of fiber volume fractions. The appropriate increase in fiber orientation can improve the EA and the CFE of the composites. The EA of reinforced composites with sinusoidal fiber is 66% higher than that of the ones with straight fiber. Three damage modes were identified by combining the damage process images corresponding to the compressive load–displacement curves and the morphologies of the crushed composites. The EA mechanism of the new composites was analyzed by observing the damage process of the AAFRCs. Highlights: A novel CoFeSiB amorphous alloy fiber reinforced epoxy composites.The increase in fiber orientation improves the energy absorption and the crush force efficiency of the composites.The energy absorption of reinforced composites with sinusoidal fiber is higher than that of the composites with straight fiber.Three damage modes were identified: compression damage, axial bending and transverse shear. [ABSTRACT FROM AUTHOR]

Highlights Variable stiffness (VS) composite structures can significantly reduce weight by adjusting fiber orientation. However, in current designs, the directional properties of composites cannot be fully utilized due to the lack of comprehensive mechanical characterization of VS laminates. This paper aims to investigate the compressive and out‐of‐plane bending behavior of steered laminates. Firstly, the critical steering radius theory was studied and derived. Secondly, five steered laminates with different radii and one “baseline” laminate were designed, manufactured, and tested to examine the effects of fiber steering on compressive and interlaminar shear strength (ILSS). The results indicate that, compared to the “baseline” laminate, the steered laminates exhibit a decreasing trend in both compressive strength and ILSS, with the maximum reductions being 32.1% in compressive strength and 9% in shear strength. Meanwhile, the microstructure was observed to gain an in‐depth understanding of the changes in the mechanical properties of the steered laminates. This study comprehensively evaluates the mechanical performance of steered laminates and provides appropriate steering limits for the design and manufacture of VS structures. The critical steering radius theory was studied and derived. Five steered laminates with different radii and one “baseline” laminate were designed, manufactured, and tested to examine the effects of fiber steering on compressive and ILSS. The microstructure was observed to gain an in‐depth understanding of the changes in the mechanical properties of the steered laminates. [ABSTRACT FROM AUTHOR]

This study investigates the crashworthiness of biomimetic composite thin‐walled tubes under quasi‐static axial crushing, focusing on the effects of geometric structure and fiber orientation. The thin‐walled tubes, inspired by honeycomb structures, were manufactured using carbon fiber composites through multi‐cavity preform mold method. Quasi‐static crushing tests and CT scanning observation were conducted to characterize the mechanical response, crashworthiness mechanisms and energy absorption capacity of the thin‐walled tubes. Results demonstrated excellent energy absorption capacities across all configurations, with the C‐0/45 configuration achieving the highest specific energy absorption at 115.03 kJ/kg. The optimal crushing energy absorption process for thin‐walled tubes involves achieving high peak loads and maintaining high load levels. Sustaining high loads requires progressive and stable damage without the formation of extensive intermediate cracks between different plies (indicative of strong interlaminar shear strength). The structural integrity of the uncrushed sections must remain intact without significant damage during the crushing process. Fiber orientation parallel to the loading direction enhances peak load levels and interlaminar shear strength between plies, but may compromise circumferential stiffness and structural stability. The influence of geometric configuration is primarily manifested in the progressive and stable crushing phase, where the tube requires sufficient space to accumulate its own debris without causing damage to the uncrushed thin‐walled structure. Highlights: Structures and fiber orientation boost crashworthiness in biomimetic composite tubes.Biomimetic structures were produced using a multi‐cavity preform mold method.CT scans were conducted to characterize the energy absorption mechanisms.Composite tubes demonstrated excellent energy absorption capacity of 115 kJ/kg. [ABSTRACT FROM AUTHOR]

The characterization of the flexural performances of short glass fiber reinforced polyether‐ether‐ketone (SGFR‐PEEK) composites fabricated by injection molding is a crucial and challenging task due to the process‐induced fiber orientation at different locations, resulting layered shell‐core‐shell microstructures and exhibiting large variations in mechanical performances. This article proposes a method for predicting the bending performance of SGFR‐PEEK and indicates the influence of fiber orientation on its bending behavior. This article reports a new scheme that combines multiscale homogenization with periodic microstructures and presents an experimental investigation of the flexural properties of SGFR‐PEEK composites. The distributions of fiber orientation through the thickness extracted from the micro‐computed tomography (μCT) were analyzed and reproduced with a layered skin‐shell‐core structure along the thickness at meso‐scale finite element model within representative volume elements (RVEs) of the macroscopic composites. Then, the effective properties of the RVEs were predicted using the homogenization method with the periodic boundary condition. The elastic modulus of skin‐shell‐core layers in the direction of flow are 4260.51, 4541.27, 4628.52, and 4630.84 MPa, respectively. The classical laminate theory (CLT) and the second homogenization implementation were then utilized in conjunction with the obtained mechanical properties of RVEs to predict the effective macrostructural behavior. The flexural modulus of the composite material was determined to be 5448.7 MPa through a three‐point bending test. The results obtained through lamination plate reinforcement theory and finite element simulation were 5887.4 and 5785.9 MPa, respectively, showing good agreement with the experimental findings. It is shown that the proposed multiscale scheme yields satisfactory agreement with experimental measurements. In addition, the effect of layered skin‐shell‐core microstructures on the flexural behavior was discussed. Highlights: RVEs of layered shell‐core‐shell microstructures were generated with specified fiber orientations.The homogenization scheme with the periodic boundary condition was adopted to accurately predict each layer mechanical properties.The proposed multiscale scheme was compared with experimental results and yielded satisfactory predictions.The effect of layered skin‐shell‐core microstructures on the flexural behavior was thoroughly studied by the multiscale analytical approach. [ABSTRACT FROM AUTHOR]

The rapid advancement of polymer composites, particularly those reinforced with hybrid kenaf, has positioned them as viable structural materials across diverse industries such as automotive, defense, aerospace, marine, construction, and naval. Despite their growing popularity, recent advances in kenaf yarn‐reinforced thermoplastic acrylonitrile butadiene styrene (ABS) composites for structural applications need more comprehensive coverage in the literature. This article addresses this gap by critically examining the influence of quasi‐isotropic stacking orientation on water absorption, flexural strength, and impact properties in kenaf yarn fiber‐reinforced ABS composites. Prepared using hand layup and compression molding techniques, the composites featured varying stacking orientations, including 0°/0°/0°/0°, 0°/90°/0°/90°, −45°/90°/0°/45°, 90°/−45°/0°/45°, 90°/0°/45°/−45°, and 0°/45°/−45°/90° for kenaf yarn reinforced ABS. The findings reveal that the 0°/45°/−45°/90° configuration offers the best overall mechanical properties and water penetration resistance among quasi‐isotropic stacking sequences, exhibiting low water uptake and higher tensile and flexural strengths of 35.3 and 85.4 MPa, respectively, compared to other sequences. This suggests that incorporating ±45° plies contributes to a balanced distribution of mechanical strength and modulus across different directions, making the 0°/45°/−45°/90° configuration ideal for high‐strength structural applications in kenaf yarn/ABS composites. Highlights: Fiber stacking orientation is the key factor affecting the mechanical performance of kenaf‐based composites.Using the hand layup technique, six stacking orientations (0°/0°/0°/0°, 0°/90°/0°/90°, −45°/90°/0°/45°, 90°/−45°/0°/45°, 90°/0°/45°/−45°, and 0°/45°/−45°/90°) were employed to create kenaf fiber‐reinforced ABS composites.A quasi‐isotropic sequence of 0°/45°/−45°/90° allows the least water penetration due to the strategic placement of ±45° plies in the middle layers of composites.0°/45°/−45°/90° configuration offers the best flexural and tensile properties due to better force distribution within the ±45° plies in the middle layers.Under surface morphological analysis, the optimal fiber stacking sequence contributes to fewer voids and fiber pull‐outs. [ABSTRACT FROM AUTHOR]

This research investigates the impact of weld lines on the mechanical properties and fracture behavior of injection‐molded unfilled and glass fiber‐reinforced polyamide 6 (PA6). The study aims to predict the weld line strength by analyzing the composite's microstructure at the weld line and investigating the influence of injection molding parameters. While weld lines had minimal effects in unfilled PA6 thanks to the matrix's high healing capability, composite samples showed reduced mechanical properties due to unfavorable fiber orientation at the weld line. Fracture surfaces revealed a bell‐shaped structure linked to the 'underflow' process caused by flow imbalances during injection molding. This phenomenon impacts fiber orientation at the weld line, affecting mechanical properties. The 'underflow' is simulated using Autodesk Moldflow®, predicting enhanced fiber alignment along the flow direction. Regarding processing parameters, both melt and mold temperatures showed negligible impacts, while enhanced mechanical properties were observed at elevated packing pressures. The analysis of fracture surfaces showed intensified "underflow" with increased packing pressure. A relationship is established between weld line strength and fiber orientation at the weld line, potentially serving as a predictive tool for estimating weld line strength. Highlights: Weld lines in unfilled PA6:Negligible impact on the mechanical properties.In the PA6 composite: significant drop due to unfavorable fiber orientation.Fracture behavior of the composite: Bell‐shaped weld line linked to "underflow."Melt and mold temperature: minor effect; packing pressure enhances properties.Correlation established between the weld line strength and fiber orientation. [ABSTRACT FROM AUTHOR]

To distinguish the grinding performance of the multidirectional (MD) and unidirectional (UD) carbon fiber‐reinforced thermoplastic (CFRTP) composites, MD and UD carbon fiber‐reinforced poly‐etherether‐ketone (CF/PEEK) composites were employed in this study. Different ply stacking sequences and process parameters were set for grinding experiments. Subsequently, the surface morphologies and roughness were observed and measured. Experimental results indicated that the variations of grinding forces with grinding parameters of MD‐CF/PEEK and UD‐CF/PEEK were consistent. However, the heat transfer mechanism and the effects of grinding parameters on the maximum grinding temperatures were different between the two composites. The grinding forces and temperatures of MD‐CF/PEEK were slightly lower than UD‐CF/PEEK, and MD‐CF/PEEK reached better surface quality under the same parameters, indicating that the grinding performance of MD‐CF/PEEK was not the simple superposition of UD‐CF/PEEK. In addition, the chip formation and material removal mechanism of CF/PEEK were investigated. The grinding performance of MD‐CF/PEEK was primarily dependent on the θ elements of laminate while the grinding performance of UD‐CF/PEEK was closely related to the fiber orientation angles during grinding. This study established a more in‐depth understanding into the grinding performance of MD‐CF/PEEK and provided technical guidance for high‐quality grinding of CFRTP. Highlights: The grinding performance of the multidirectional (MD) and unidirectional (UD) carbon fiber‐reinforced poly‐etherether‐ketone (CF/PEEK) is compared.The grinding forces and temperatures of MD‐CF/PEEK are slightly lower than that of UD‐CF/PEEK, and the MD‐CF/PEEK reach a better surface quality under the same grinding parameters.The grinding performance of MD‐CF/PEEK is primarily dependent on the θ elements of laminate, and the change of layering order is not a critical factor.The grinding performance of UD‐CF/PEEK is closely related to the fiber orientation angles during the grinding process.The surface quality of MD‐CFRTP can be effectively improved by reducing the grinding depth and feed speed, and increasing the grinding wheel speed. [ABSTRACT FROM AUTHOR]

In this paper, nine different carbon fiber laminates containing clusters are designed using the ant colony ACO algorithm, which have similar equivalent bending stiffnesses and B‐matrices, with the differences being the fiber orientation of the clusters and the position of the clusters in the laminates. The dynamic mechanical characterization of laminates for low velocity impact (LVI) at three different energies was carried out by means of a falling weight impact experiment. The experimental results show that the main form of failure of the laminate is delamination failure at low energy impacts, and shear fracture becomes more and more obvious with the elevation of the impact energy, which was observed in detail by the stereo microscope and electron microscope. The damage area of the laminate and the force and displacement curves after 30 J energy impact were compared by x‐ray scanning to derive the effects of the angle of the ply cluster fibers and the different positions of the ply clusters in the laminate on the impact resistance of the laminate. In conclusion, when designing the laminate, consideration should be given to designing 45° clusters on the impacted side and 90° clusters in the middle layer of the laminate to obtain the best impact resistance. Highlights: Designed 9 types of laminates with different laminate structures based on ACO algorithm.Different laminates have similar equivalent bending stiffnesses and the B matrix as close to 0 as possible.LVI tests at three energies were performed on 9 types of laminates.The effects of different orientations of the clusters and the position of the clusters in the laminate on the impact resistance of the laminate were investigated. [ABSTRACT FROM AUTHOR]

In this work, a new approach is proposed for predicting the life to crack initiation in Short Fiber Reinforced Polymers (SFRPs) under cyclic loadings in the presence of notches, cut‐outs and stress concentrations. A multiscale model is presented, encompassing two length scales for correlating the applied loads to the local stress fields in the matrix. These are used for defining an effective stress for predicting the life to crack initiation, accounting for the simultaneous influence of the notch geometry, the fiber content, orientation and distribution. The criterion was successfully validated on a large set of experimental results. Highlights: A new model is proposed for predicting fatigue crack initiation in notched SFRPsThe model is based on a multiscale procedurePrediction is based on local matrix stresses averaged in a structural volumeThe model accounts for fiber orientation, distribution and notch geometry [ABSTRACT FROM AUTHOR]

Drilling glass fiber reinforced polymer matrix (GFRP) composites typically causes burrs, splintering, and microcracks within the GFRP structure, as well as delamination, fiber pull‐out, and thermal degradation of the polymer matrix. Designing and manufacturing molded‐hole GFRP components, as opposed to drilling, has recently been proposed as a promising method for overcoming the issues associated with drilling, for which there is limited research. Specifically, the mechanical response of molded‐hole GFRP has not been fully addressed in the literature. In the present study, molded and drilled GFRP composites with epoxy matrix were fabricated by hand lay‐up, and then the samples were analyzed utilizing experimental and numerical analysis techniques. Stress and strain analyses of GFRP samples were performed in Ansys Transient Structural Analysis. Although the fiber orientations of the layer geometries [0°/90°] and 3D models were the same, an additional layer was defined in the direction of the fiber orientation [45°/−45°] of molded‐hole composites to simulate the fiber accumulation effect. Experimental findings revealed that the flexural strength of molded composites was 12% greater than that of drilled composites. According to the numerical analysis, 98.7% proximity was achieved between the experimental and numerical results. Thus, the present study has provided numerical modeling to understand the flexural strength of molded composites for the first time, which will contribute to the increased use of molded composites in numerous applications in the fields of aerospace, automotive, and marine. Highlights: Drilled‐ and molded‐hole GFRP composites were produced by hand lay‐up.Flexural properties of the composites were examined via 4P bending tests.Flexural strength of molded composites was higher than that of drilled ones.98.7% proximity was achieved between the experimental and FEM results.A unified FEM method is proposed for the molded‐hole composites. [ABSTRACT FROM AUTHOR]

In the current research investigation, jute and sisal intra‐hybrid woven fabric were specifically tailored to maintain jute and sisal in weft and warp directions, respectively. Jute sisal intra‐hybrid composites were prepared with four layers of intra‐hybrid woven fibers using a compression molding technique. Physical, mechanical (static and dynamic), and thermal stability behavior were investigated, and their structure–property relationship has been established. The obtained results showed that jute‐sisal cross‐interplay‐based hybrid composites recorded maximum tensile and flexural modulus values with minimum anisotropy. It can be concluded from the current experimental investigation that weft/warp orientation and stacking sequence play a significant role in defining the mechanical performance and anisotropic nature of woven fiber‐reinforced laminated composites. Also, the anisotropic properties can be minimized by investigating the effect of fiber orientation and hybridization of natural fibers‐based laminated composites. Highlights: Woven mats were tailored to orient different fibers in warp and weft directions.The influence of the fiber's orientation and stacking sequence was analyzed.Fiber orientation and hybridization have influenced mechanical performance.The alternative stacking sequence has shown the highest mechanical properties. [ABSTRACT FROM AUTHOR]

Manufacturing and investigating metallic‐glass‐fiber‐reinforced epoxies is an important new attempt to present their potential to contribute to the aviation industry. In order to explore the energy absorption in novel CoFeSiB metallic‐glass‐fiber/epoxy resin composites, CoFeSiB/epoxy resin composite cylinders with different fiber volume fractions were prepared by a hot‐pressing method. The amorphism of the metal fibers was analyzed using x‐ray diffraction. The quasi‐static compression tests were performed on different fiber oriented samples with a diameter of 3.6 mm and a height of 7.2 mm. The sample with the fiber orientation [0°/90°] has a higher energy absorption capacity, compared to the one with the fiber orientation [0°/0°]. The dynamic‐ compression tests were performed on the [0°/0°] samples with a diameter of 3 mm and height of 6 mm at different air pressures. The compression fracture surfaces were examined by scanning electron microscope. Then the energy absorption mechanism of the composites was investigated. This study is of great significance for the energy absorption in amorphous metal fiber/epoxy composites. [ABSTRACT FROM AUTHOR]

The present paper highlights the benefits of multiaxially reinforced profiles manufactured by out of die ultraviolet (UV) cured pultrusion. Thanks to the low pulling forces inherent to this technology, we could manufacture a quasi‐isotropic laminate with high fiber content (62% in volume). Even if just one fifth of the reinforcement was arranged longitudinally, the fiber orientation at the ±45° and 90° layers was not distorted. The in‐plane properties of this new balanced reinforcement configuration improved the impact and notched resistance compared to a reference configuration typical of conventional pultrusion, consisting of roving and continuous strand mats. Additionally, the tensile strength achieved in the transversal direction for the new configuration was an order of magnitude higher. Therefore, this novel technology has the potential to broaden the applications targeted by pultrusion to those where multiaxial load cases could be encountered. Highlights: Multiaxially reinforced profiles were made by out of die UV cured pultrusion.These profiles presented enhanced in‐plane properties.Impact resistance was better than that of a typical reinforcement configuration.Notched tensile strength was also improved in both principal directions. [ABSTRACT FROM AUTHOR]

The orientation of fibers in polymer matrix plays a crucial role in governing the performance of composites including friction and wear. In the present work, the effect of fiber orientation on tribological behavior of 3D printed short carbon fiber reinforced PEEK composites (CF/PEEK) was studied by two series of tribo‐tests, namely macro‐scale continuous sliding and micro‐scale multiple scratching. Fiber orientations studied included parallel, tilted and anti‐parallel relative to the sliding direction in both macro sliding and micro scratching. It was revealed that the effect of fiber orientation showed strong dependence on applied loads. In most cases, lower wear were obtained when the fiber orientation was tilted rather than parallel or anti‐parallel in macro continuous sliding. With tilted orientation, the composite also exhibited the best scratching behavior except for that at the lowest normal load. To reveal the mechanisms behind this orientation effects, the composite's worn surface, as well as those of the counter rings, were characterized. Findings of the present work indicates that scratching tests can help understand the macro sliding mechanisms and appropriate fiber orientation is beneficial in improving the tribological properties of polymer composites, which can be realized through 3D printing. Highlights: PEEK composites filled with highly oriented carbon fibers were manufactured by fused deposition modeling (FDM).Tribological anisotropy was studied through macro sliding and micro scratching measurements with respect to carbon fiber orientation.The coupling mechanism of load and fiber orientation was discussed in influencing the composites' friction and wear properties. [ABSTRACT FROM AUTHOR]

T‐300 6K carbon fabric fiber‐reinforced epoxy laminated composites are prepared by in‐situ and hot‐compression molding technique. The main emphasis of this study is to examine the impact of the structural deformations on fiber orientations of laminated composites during vibrational damping, stiffness, and electromagnetic interference (EMI) shielding properties. The damping properties of carbon fiber laminated composites are analyzed in terms of natural frequency and logarithmic decrement. The digital image correlation technique has been used to measure the mode shape behavior of carbon fiber reinforced polymer (CFRP) composites. The dynamic behavior of the CFRP laminated composites has significant effect on the fiber orientations in terms of storage, loss modulus, and damping ratio. The value of EMI shielding of CFRP laminated composites of T‐300 6K based CFRP polymer laminated composites has slight variations in the SET and their values are 107.17 (B‐45), 106.33 (B‐30), and 110.0 dB (B‐0). The vibrational and EMI shielding properties are showing a huge potential for these kinds of CFRP laminated composites in military and aircraft applications. Highlights: CFRP laminated epoxy composites were fabricated by hand layup technique.The ply orientation of CFRP composites were affected the mechanical properties.DIC was used to determine the mode shapes of laminated composites.CFRP laminated composite exhibited excellent EMI properties. [ABSTRACT FROM AUTHOR]

In the current study, the friction and wear properties of Furcraea foetida fiber‐reinforced epoxy composites were investigated. This study evaluated the effect of Furcraea foetida fiber content on the tribological behavior of composites. A water‐retting method was employed to extract the fibers, and resin transfer molding was used to fabricate the composites. The frictional force, coefficient of friction (COF), and wear rate were measured under dry test conditions and various applied loads (80, 100, 120, and 140 N). Microstructural analysis was conducted using scanning electron microscopy to investigate the surface morphology and wear mechanisms of the composites. The results revealed that the composite with 50 vol% of fibers exhibits the lowest frictional force and COF in both normal and parallel orientations with overall average COF of 0.43 in normal orientation and 0.42 in parallel orientation. Moreover, the composite with 60 vol% demonstrates the best wear resistance with an overall average specific wear rate of 2.1982 × 10−5mm3/Nm in normal orientation and 4.3478 × (10−5) mm3/Nm in parallel orientation. Overall, this study provides valuable insights into the tribological behavior of Furcraea foetida fiber‐reinforced epoxy composites and identifies the optimal volume fractions for improved friction and wear performance. Highlights: Higher vol% yields denser composites with minimized voids.Normal fiber orientation shows maximum SWR of 10.0614 × (10−5) mm3/Nm.Optimal frictional force and COF in 50 vol% composite.Enhanced wear resistance observed in 60 vol% composite.Higher vol% increases interfacial bonding and wear resistance in composites. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the mechanical properties of carbon fiber reinforced epoxy composites (CFRECs) filled with Graphene (Gr) and Silicon Carbide (SiC) nanoparticles. Gr and SiC nanoparticle filled CFREC plates at 0%, 0.5%, 1%, and 2% weight ratios were fabricated using a vacuum infusion technique from unidirectional carbon fiber fabric with both 0 and 90° fiber orientation. According to ASTM standards, tensile, compression, and three point bending tests were performed to determine the effects of additive type and weight ratios. CFRECs with Gr additive exhibit improved tensile properties compared to the unfilled composites, especially at higher filler contents and at specific fiber orientations. Also, the Gr additive showed a better improvement in the tensile behavior of the CFRECs than the SiC additive. In general, it was found that the elastic modulus values of nanoparticle additive samples were higher than that of the unfilled composite material in both fiber orientations. Except for the 0.5% SiC ratio with 0° fiber orientation, the particle added nanocomposites did not exceed the value of the unfilled composite and did not make a positive effect on the compressive strength. It has been observed that Gr additives give more positive results on the bending strength of CFRECs than SiC, especially at a 2% weight ratio. Highlights: Effects of nanoparticle types on mechanical properties of CFRECs were compared.Weight ratio effects on the properties of nanoparticle‐filled CFRECs were studied.The load‐bearing capacity decreased as the additive ratio increased.Additives and ratios should be carefully selected for the intended applications.Overall, presence Gr resulted in enhanced properties much prominently for composites. [ABSTRACT FROM AUTHOR]

In the process of preparing textile composites by resin transfer molding (RTM) method, both the upper and lower surface of the mold will interact with the composite parts due to the mismatch of thermal expansion coefficient between the mold and the part, resulting in warpage deformation. To address this key technical problem, this article first studied the effect of mold on the warpage deformation of composite material under different fiber volume fractions. Then a mold–part interaction modeling method for RTM process with nonthermoelastic deformation is proposed. By introducing shear layers between the upper and lower surfaces of the mold and the composite part, a finite element simulation model for predicting the curing deformation of the component is established and experimentally verified. The results show that the effect of mold–part interaction on the warpage deformation of the composite decreases with increasing fiber volume fraction. Meanwhile, the proposed modeling method can avoid complete material characterization, and the comparison between experimental and simulation results proves that the model can accurately simulate the curing deformation of composite components under the same process conditions. Finally, the analysis reveals that the interaction caused by thermal mismatch between the composites and the mold is less related to the intermediate layup, but mainly related to the fiber orientation of the layup layer in contact with the mold. Highlights: The warpage deformation law of the mold on the composites with different fiber volume fractions is investigated.A mold–part interaction modeling method for a resin transfer molding process with nonthermoelastic deformation is proposed, where the mold stretching effect is represented by the cumulative effect of the interaction between the two layers on the upper and lower surfaces of the part. [ABSTRACT FROM AUTHOR]

This paper investigates the scratch behavior of carbon fiber reinforced composites (CFRCs) under thermal aging conditions. Scratch depth was analyzed with respect to three parameters: velocity, thermal cycle, and direction of the scratch. The results showed that thermal aging has a significant effect on the scratch behavior of CFRCs, with an increase in thermal cycle leading to an increase in scratch depth. The scratch depth was also found to be greater in the weft direction compared to the warp direction, which can be attributed to the difference in fiber arrangement and orientation in the CFRC material. The analysis of variance (ANOVA) was performed to investigate the effect of thermal aging on the scratch behavior of CFRCs. The ANOVA results revealed that the direction of the scratch has a significant effect on scratch depth, with the weft direction showing greater scratch depth compared to the warp direction. The surface roughness of CFRCs was analyzed under thermal aging conditions and with an increase in thermal cycle leading to an increase in surface roughness. The roughness values were found to be higher in the weft direction compared to the warp direction, which can be attributed to the difference in fiber arrangement and orientation in the CFRC material. [ABSTRACT FROM AUTHOR]

Material flow and associated fiber orientation are among the most important features in Large Area extrusion deposition Additive Manufacturing (LAAM) of short fiber‐filled composites. Endeavors have been done in 2D flow models, where significant knowledge is achieved in explaining the material anisotropy of the deposited composite parts. Nevertheless, 2D flow models are limited by a couple of assumptions that lose significant characters of the deposition flow. This study is one of the first few that employ a 3D flow model which focuses on the quasi‐steady state of the polymer composite melt flow within the nozzle and the subsequent 90‐degree turning deposition onto the material substrate. The material flow is assumed as a highly viscous Newtonian flow. The fiber orientation is evaluated using the advanced pARD‐RSC fiber orientation tensor evaluation model, via the one‐way weakly‐coupled flow/orientation analysis formulation. Computed results show the fiber orientation state on the entire cross‐section of a deposited bead, which yields a clear view of how the material anisotropy is affected by the locally varied fiber orientation. The 3D‐flow prediction proves that the transverse directional fiber alignments are in high degree of similarity as compared to the over‐predicted results from the simplified 2D planar flows. In addition, the 3D‐model results exhibit a more favorable agreement with the reported experimental data than that yielded by the conventional 2D models. [ABSTRACT FROM AUTHOR]

Non‐asbestos gaskets have high tensile properties, good permeability resistance, and resilience. Compared with traditional asbestos gaskets, non‐asbestos gaskets have the advantages of less pollution and no harm to human body. This manuscript presented an experimental and theoretical study of aramid fiber reinforced non‐asbestos gaskets. The tensile strength of gaskets with different fiber orientations and tensile rate were conducted in order to meet the industrial standard. The leakage rates of nondestructive non‐asbestos gaskets with different sizes under different medium pressures and pretightening load were investigated. The results showed that the leakage rate can reach the industrial standard when the pretightening load reached 30 MPa and medium pressures was less than 2 MPa. The artificial scratch defects were made on non‐asbestos gaskets, and the effect of the width and depth of the scratch defect on leakage rate was further investigated. The sealing failure would occur when the scratch depth reached 0.1 mm. The modified model containing defect factors was established. The results showed that the modified model can well characterize leakage rate of gasket. [ABSTRACT FROM AUTHOR]

Fiber orientation deviation is a typical defect type in carbon fiber reinforced polymer composites (CFRPs) manufacturing process. Unlike other defect types, fiber orientation deviation has minimal influence on the local conductivity of CFRPs, so it is difficult to be detected by eddy current (EC) detection methods. Based on the principle of eddy‐current equilibrium, a new method is proposed in this paper to improve the sensitivity of fiber orientation detection. In this method, an EC field with eddy‐current equilibrium distribution inside the specimen is excited by means of a special double D‐shaped probe. When there is a deviation from the fiber orientation, the eddy‐current equilibrium state is broken, resulting in a rapid increase in the intensity and distribution range of the induced EC inside the specimen, and finally lead to a drastic change in the probe signal. The experimental results show that the double D‐shaped probe with an eddy‐current equilibrium effect can detect the fiber orientation of CFRPs, and the changes in fiber orientation can cause up to a 423.1% variation in the probe signal. Compared with the traditional rectangular probe, the designed probe is more sensitive than the former to small changes in fiber orientation in the range of −20° to 20° under high frequency excitation above 3 MHz. In addition, the proposed method can also be used for rapidly identifying fiber waviness with a deviation angle of 7.4° inside unidirectional CFRPs, which can be achieved effectively and intuitively through defect imaging. [ABSTRACT FROM AUTHOR]

Natural fiber composites are currently considered to be the most sustainable and renewable substitute for synthetic fiber composites in several low and medium‐density applications. Various research works are ongoing to evaluate the machinability of plant‐based natural fiber composites. In the current investigation, an attempt has been made to fabricate and examine the drilling behavior of Typha angustifolia fiber reinforced (TAFR) composite. Composites were manufactured using Typha angustifolia fibers in unidirectional (UD) and bidirectional (BD) orientations using the epoxy matrix through the compression molding technique. Fibers were characterized using the X‐ray diffraction method to determine the crystallinity index and crystallite size. Drilling experiments were conducted on TAFR composites and using Taguchi's L18 mixed‐level design with various process parameters the experiments were conducted. The optimal experimental combination rendering the lowest value of exit delamination and thrust force was determined using Taguchi‐TOPSIS hybrid approach. A quadratic model was also developed to predict the response of drilling. Drilled hole morphology was analyzed using scanning electron microscopy to know about various failure mechanisms and damages induced during the drilling operations. It was found from the results that the lowest speed and feed rate and higher drill diameter rendered minimal delamination and thrust force for both UD and BD TAFR composites. [ABSTRACT FROM AUTHOR]

This study investigated the friction and wear properties of high‐strength polyacrylonitrile (HS‐PAN)‐, high‐modulus polyacrylonitrile (HM‐PAN)‐, and high‐modulus pitch (HM‐pitch)‐based carbon fiber‐reinforced polymer matrix composites (CFRPs) with silicon carbide (SiC) nanoparticles. The fiber orientation of the CFRP specimens was set as 8‐ply unidirectional laminates, denoted as [0]8. Ball‐on‐disk (cyclic) wear testing was accompanied by laser, digital, and scanning electron microscope observations. For the HS‐PAN CFRP, the coefficient of friction and wear resistance were the highest among the HM‐PAN and HM‐pitch CFRPs and wear resistance was improved by the addition of SiC‐nanoparticles. Furthermore, there was no significant enhancement of wear resistance for the SiC‐nanoparticle‐filled and nanoparticle‐unfilled HM‐PAN CFRP. The wear resistance was improved by adding SiC‐nanoparticles for the HM‐pitch CFRP. [ABSTRACT FROM AUTHOR]

A complete study on the relation between the injection molding parameters and the resulting fiber length, orientation and mechanical properties is presented for highly reinforced long fiber thermoplastic (LFT) polypropylene (PP). It has been found that the longest fibers obtained are the ones processed with the lowest backpressure and the highest screw speed. The backpressure gains importance over screw speed when the amount of glass fiber reinforcement increases, contrary to what was found for less reinforced thermoplastics. The injection speed does not influence the fiber breakage phenomena, while it has great importance in fiber orientation and thus on the tensile strength, especially when the weight fiber average length is below 1000 μm. When this average is over 1000 μm, fibers begin to weave a mesh that thickens the core region and hinds its orientation, reducing the tensile strength but improving impact resistance. [ABSTRACT FROM AUTHOR]

Prepreg platelet molding compound (PPMC) can be used to create structural grade material with a heterogeneous mesoscale morphology. The present work considered various platelet lengths of the prepreg system IM7/8552 to study the effect of platelet length on the flexural behavior of PPMC composite. A progressive failure finite‐element analysis was used to understand competing failure modes in PPMC with the different platelet length. The interlaminar and in‐plane damage mechanisms were employed to describe complex failure modes within the mesostructure of PPMCs. Experimental results of the flexural tests of the PPMC with different platelet length sizes were used to validate the modeling prediction. The experimental and modeling results revealed complex behavior of the flexural mechanical properties (modulus and strength) on the platelet length. The experimental results indicate that PPMC composites processed with a plate length of 12.7 mm have a higher flexural modulus and strength than 25.4 and 6.35 mm. The platelet length effect on the flexural mechanical behavior was attributed to interactions between various damage mechanisms and the stochastic fiber orientation distribution variability in the material. [ABSTRACT FROM AUTHOR]

Short‐fiber‐reinforced‐materials are widely used in industry today. In this paper, microstructure and modal analyses are performed on short‐glass‐fiber‐reinforced polypropylene (PPGF) and short‐natural‐fiber‐reinforced polypropylene (PPNF), to study possible links between the first natural frequency and fibers' orientation and quantify the associated variability. In view of this, different specimens were tested with clamped‐free boundary conditions. The microstructural analysis, performed with micro‐computed tomography studies fibers' properties in injection‐molded plates. This study shows the importance of considering real fibers' orientation for modal predictions. [ABSTRACT FROM AUTHOR]

In injection and compression molding simulation, orientation tensors provide an efficient way with less computational effort to calculate flow‐induced fiber orientations. In these flow calculations, the solution of any even‐ordered orientation tensor needs the following even higher‐ordered orientation tensor. Therefore, a closure is used in order to approximate the higher‐ordered orientation tensor as a function of the components of the lower‐ordered orientation tensors. There exist many closures of the fourth‐order orientation tensor in terms of the second‐order orientation. This paper gives a review with mathematical details for different closure approximations including simple closures, composite closures, eigenvalue‐ based orthotropic closures, invariant‐based closures, and neural‐network‐ based closures. Moreover, a new closure approximation that assumes an orthotropic stiffness tensor was suggested in this work. The results of the closure approximations were validated through the comparison of Young moduli between the closure approximations and the experimental results for both short‐ and long‐fiber‐reinforced composites. [ABSTRACT FROM AUTHOR]

Two‐parameter Weibull reliability plots are utilized to determine the effects of strain rate on the interfacial strengths of unidirectional carbon fiber reinforced epoxy (CFRE) composites. Laminate specimens with two different fiber orientations are tested to failure under flexural loading. Type 1 laminates with fibers running parallel to specimen length (fiber orientation of 0° with respect to specimen span length) enable measuring inter‐laminar shear strength (ILSS) of the interface (between adjacent lamina) with locus of failure along beam mid ply. Seventy‐two type 1 laminates are tested at five levels of flexural strain rates: 1.89 * 10−5 to 9.37 * 10−2 s−1. Type 2 laminates with fibers running perpendicular to specimen length (fiber orientation of 90° with respect to specimen span length) enable measuring intra‐laminar (matrix/fiber) peel strength (ILPS) for tensile (mode I) strength of the matrix/fiber interface with locus of failure at beam bottom ply. Thirty‐six type 2 laminates are tested at three levels of flexural strain rates: 2.09 * 10−5 to 3.49 * 10−3 s−1. For each level of strain rate, Weibull plots are constructed. Stress values at failure probability (Pf) of 63.1% are assigned as strength values. The results show a slight decrease of the Weibull modulus, m, with increasing strain rates. The modulus decreases from 12.37 to 10.49 and from 11.11 to 9.68, for laminates type 1 and 2, respectively. For laminates type 1, ILSS increases with increasing strain rates rising 16.1% over the range of the tested strain rates. For laminates type 2, ILPS increases with increasing strain rates rising 38.1% over the range. Two‐parameter Weibull reliability plots are constructed to determine the sensitivity to applied strain rate of the interfacial strengths of unidirectional graphite carbon fiber reinforced epoxy (CFRE) composites. Experimental measurements were made at five different strain rates of the inter‐laminar shear strength (ILSS) of the interface between adjacent lamina. Also measured was the intra‐laminar (matrix/fiber) peel strength (ILPS) for the tensile (mode I) strength at three different strain rates. Both ILSS and ILPS were found to be sensitive to applied strain rate (at room temperature) with strengths values increasing with increasing rates. [ABSTRACT FROM AUTHOR]

The recent‐emerging Large Area extrusion deposition Additive Manufacturing (LAAM) provides a low‐cost and high‐efficient alternative manufacturing approach for industries like automotive and aerospace. Fiber orientation information significantly determines the material performances of LAAM‐produced short fiber reinforced composites. Numerical studies have been performed to better understand the microstructural formation of the fiber orientation in deposited beads. The fully coupled flow/orientation analysis approach has been applied for LAAM deposition flow modeling. In contrast, the orientation analysis is still limited to the classic Folgar‐Tucker Isotropic Rotary Diffusion (IRD) model. This paper employs the advanced principle Anisotropic Rotary Diffusion Reduced Strain Closure (pARD‐RSC) orientation evaluation model to estimate the fiber alignment of the LAAM flows, which is firstly used in the simulations of extrusion deposition flows with free surface boundaries. The effects of constant parameters of the pARD‐RSC model are investigated. It is found that predicted fiber orientation results in the flow end are primarily sensitive to the value of the strain slip factor. The initial fiber orientation condition of the flow inlet is also studied. By comparing the computed results with experimentally reported data, it is found that the initial fiber orientation state of the flow inlet significantly impacts the fiber alignment patterns in the deposited beads. [ABSTRACT FROM AUTHOR]

Short fiber‐reinforced thermoplastic (SFRT) composites are drawing increasing academic and industrial interest owing to their outstanding mechanical properties, good economic efficiency, excellent designability, and recyclability. This review primarily introduces several common SFRT manufacturing methods and analyzes their advantages and disadvantages. The stress transfer and damage mechanisms in the SFRT, as well as the effects of the fiber length, fiber volume fraction, fiber orientation, fiber kinds, matrix, and interface, are discussed in depth. The review also discusses the most widely applied rule of mixture for elastic modulus prediction, the Kelly–Tyson model and the Bowyer–Bader model for strength prediction. Overall, this review summarizes the latest research developments on SFRT composites with the aim of providing literary support for their future development. [ABSTRACT FROM AUTHOR]

Injection molded fiber‐reinforced polymers have been widely used for their excellent comprehensive properties. Due to the high cost of injection molds, how to improve the strength of the products in the design stage is a problem worthy of researching. This study presents a novel method for predicting the product strength via analysis of weld line and fiber orientation, which are two key factors in injection molding. In this study, injection molding simulation was carried out in commercial software Moldex3D to obtain the information about weld line, fiber orientation and other factors which were used for prediction of strength of products. Based on the healing theory and interdiffusion model, a weld line strength model for injection molding is established. The effects of fiber orientation distribution on strength were investigated through Abaqus structural analysis. The proposed method was used to verify the experimental results in the existing literatures and the simulation results were in good agreement with the experiments. The method was applied in the gate design of an aerospace product. This study indicated that the proposed method has great potential for mold design, product structure design and process optimization. [ABSTRACT FROM AUTHOR]

In this study, a comparative analysis of basalt, E‐glass and hybrid fiber reinforced vinyl ester composites was carried out. Composites were fabricated using vacuum infusion process with 0°/90° and ±45° as fiber orientation angles. The influence of volume fraction on mechanical behaviors and surface morphology of impact fractured composites were analyzed. The glass and basalt fibers oriented at 0° have shown higher load bearing capability, whereas the fibers oriented at 45° angle have shown higher plastic deformation. Hybridized composite having silane treated glass fibers has shown enhanced mechanical properties including tensile strength, bending strength, toughness, and elongation at break due to good bonding between fibers and polymer matrix. The tough and flexible interface between fiber and matrix dissipates more energy through stress transfer from matrix to fiber, allowing increased resistance to shearing. The impact test of BGS‐0.2 hybrid composite showed 103% and 108% of strength improvement compared to basalt (B‐0) and glass fiber (G‐0) reinforced laminates, respectively. However, the fiber orientation at 45 degree showed reduced the strength and modulus with high elongation. The fractography micrographs of hybrid composites have shown the effectiveness of basalt and glass fiber orientation in the composites and bonding between fiber and matrix indicating flexible interphase between the fiber and matrix during impact loading. The composites added with silane have shown marginal increase in water uptake due to presence of polar functional groups in the coupling agent. [ABSTRACT FROM AUTHOR]

The quasi‐static and fatigue behavior of chopped carbon fiber reinforced sheet molding compound (SMC) composite was investigated. The microstructure of material was inspected by X‐ray Computerized Tomography (XCT) and the fiber orientation distribution was analyzed. Quasi‐static tensile test was performed on specimens with different gauge length to study the size effect on mechanical properties and digital image correlation system was applied to record the strain distribution. The fatigue behavior of material was evaluated under both tension‐tension (R = 0.1) and tension‐compression (R = −1) loadings, in which XCT scanned specimens were tested to characterize the microstructure at failure location. Interrupted fatigue test was performed to observe the damage evolution process on the side surface of specimen by optical microscope and the dominant fatigue failure modes were identified. A representative volume element based modeling methodology was modified and applied to establish the relationship between heterogenous microstructure and macroscopic mechanical behaviors. The simulation results show good consistency with experimental observations which demonstrates the effect of local fiber orientation on durability performance of material. [ABSTRACT FROM AUTHOR]

As an additive manufacturing (AM) technology, fused deposition modeling (FDM) is widely used to fabricate highly complex components. Polymer components fabricated by FDM technique have weak mechanical properties. To enhance the mechanical properties, 3D printing of polymer composites is done by reinforcing particles, nanomaterials, short and continuous fibers into thermoplastic polymers. The thermal, flame retardant, and impact properties of a continuous kevlar fiber‐reinforced onyx 3D‐printed composite are investigated in this study. Additionally, the effect of fiber arrangement and orientation (0°, 90°, 0°/90°, and +45°/−45°) on the impact strength of 3D‐printed composites have been investigated. The impact strength of the 3D‐printed composite specimens was determined using izod impact testing. It was found that specimens with fiber arrangement having fiber and matrix layer configuration as 21O|20K|20O|20K|21O have a higher impact strength and specimens with fiber arrangement as 31O|40K|31O have lower impact strength. Furthermore, specimen 3D printed with a unidirectional 0° fiber angle had the highest impact strength, while specimen 3D printed with a unidirectional 90° fiber angle had the lowest impact strength. Furthermore, flammability tests and thermogravimetric analysis were performed to investigate the flame retardant and thermal properties of 3D‐printed composites. Morphological study of onyx and kevlar fiber filament was also done using scanning electron microscope (SEM). [ABSTRACT FROM AUTHOR]

A three‐dimensional (3D) microscopic finite element (FE) cutting model was developed with the thermo‐mechanical coupling for carbon fiber reinforced polymer (CFRP) composites in this article. The model predictions of cutting force, machined surface, and cutting temperature at various fiber orientations were obtained and compared with the experimental data. It was shown that the 3D microscopic cutting model can predict the cutting force, cutting temperature, and subsurface damage precisely. The behavior of cutting force has presented an obviously cyclical variation characteristics at the fiber orientations of 0°, 45°, and 90°, and different chip morphologies were obtained correspondingly. The temperature fields of machined surface were studied at the four different fiber orientations, in which the maximum residual temperature on the machined surface occurs at 90°. The heat‐induced resin coating and resin ridges on the machined surface were obviously observed at the fiber orientations of 45° and 135°. The trend curve of cutting temperature is more similar with that of thrust force by comparing with cutting force, which meaning, unlike the isotropic metal materials, the thrust force has the direct effect on the heat generation. In addition, the comparison of depth of thermal and mechanical subsurface damage was also performed, it was showed that the depths of thermal subsurface damage are close to that of mechanical subsurface damage in the range of 0°–45°, and the thermal subsurface damage decrease while the mechanical subsurface damage increases with the increase of the fiber orientation range from 90° to 180°. [ABSTRACT FROM AUTHOR]

Multiscale finite element analysis based on the asymptotic homogenization theory was carried out for short fiber reinforced plastics (FRP), and the effects of fiber morphologies on mechanical properties were systematically organized. Cellulose microfibers were used as the reinforcing fibers and polypropylene was used as the matrix. In order to quantify the enhancement effect of intrinsic fibers on the mechanical properties, a new indicator based on strain energy, contribution proportion of fiber (CPf) was proposed. In this paper, as the first demonstration of introducing the CPf, unidirectionally oriented short FRP was focused and elastic properties were analyzed for fundamental fiber morphologies. In terms of the fluctuation rate based on the elastic modulus of the matrix, when the volume content of fiber is 3.0 vol%, the elastic modulus of composites varied by 106%, 105%, 97.6%, and 35.1%, respectively, depending on the fiber orientation, fiber aspect ratio, fiber/matrix interface and fiber‐to‐fiber distance. Based on the CPf, fiber morphologies could be divided into two. The first factors are fiber orientation angle and fiber content, which determine the rate of change in mechanical properties with respect to the CPf. The second factors are fiber aspect ratio, fiber/matrix interface, and fiber‐to‐fiber distance, which affect the mechanical properties according to the rate of change determined by the first factors. The complicated influence of the fiber morphologies on the mechanical properties could be unified by introducing the CPf. These computations show that CPf is effective for systematic analysis and design of fiber morphologies. [ABSTRACT FROM AUTHOR]

The use of fiber reinforcement in large area additive manufactured components is of industrial interest due to the ability to enhance the structural properties of final processed parts. This work presents a methodology to predict the tensile, compressive, and flexural yield strength of single beads of a large‐scale, 3D printed, short‐fiber reinforced material. The methodology is built on the strength theory of Van Hattum and Bernardo, which combines the Tsai‐Wu failure criteria with Advani and Tucker's orientation averaging technique, allowing fiber orientation flow model results to serve as direct input into strength predictions. Visual advantages of the methodology such as the ability to plot spatially varying strength constants and failure plots are demonstrated. In addition, an analysis of the methodology's sensitivity to various parameters is conducted. [ABSTRACT FROM AUTHOR]

Jute and banana fibers are biodegradable green fibers being increasingly used to replace synthetic fibers in fiber‐reinforced polymer composites. Integration of jute and banana distinct natural fibers has the potential to improve composite performance in secondary structural applications. In this study, an equal quantity of unidirectional jute and banana fibers with four different fiber orientations [(0/0)3s, (0/45)3s, (0/90)3s, and (+45/−45)3s] was embedded in phenol formaldehyde resin to make hybrid laminates using the hot press method. Tensile, flexural, impact, interlaminar shear strength (ILSS), and single‐end notch bend tests are performed in accordance with the ASTM standards to evaluate the effect of fiber orientation on natural fiber hybrid composites (NFHCs). Experimental results revealed that changing the fiber orientations [(0/0)3s] leads to a major impact on reducing the mechanical properties of NFHC laminates to the extent of 39%. Furthermore, the tensile strength, Young's modulus, impact and ILSSs, and fracture toughness were found to be 37% higher for the (0°/0°)3s composite. Additionally, tensile, flexural, and impact fractured specimens were examined by scanning electron microscopy to understand the fiber–matrix failure behavior due to inter‐ply orientation in NFHCs. [ABSTRACT FROM AUTHOR]

Short fiber/polymer composites (SFPCs) are increasingly applied in the field of high‐temperature structures. Its reliability at high temperatures has always been the core issue concerned by researchers. Here, utilizing the Force–Heat Equivalence Energy Density Principle, we developed a physically based model of temperature‐dependent ultimate tensile strength (TDUTS) for SFPCs. This model quantitatively considers the evolution of residual thermal stress, interface, fiber, and matrix performance as temperature increases. Meanwhile, the influence of fiber agglomeration frequently observed in composites and fiber orientation and length distribution is taken into account in the proposed model. The model predictions over a wide temperature range are validated against the experimental data available from the literature, indicating its reasonability and accuracy. The comparison with Kelly–Tyson model and Li's model is also performed. Additionally, the quantitative effects of the fiber agglomeration and interfacial shear strength on the TDUTS are discussed in detail. The present research not only provides an accurate and feasible approach to estimate the TDUTS of SFPCs, but also offers some helpful insights for the fabrication and design of such composites. [ABSTRACT FROM AUTHOR]

The stress interaction failure criterion was applied to three compression‐molded sheet molding compound (SMC) materials. Two are epoxy‐based compounds with randomly oriented carbon fiber tows, and the third material consists of glass fiber bundles randomly oriented in a vinyl ester resin. The failure surface was built using tensile test results at different orientations with respect to the flow direction, resulting in combined loads in the principal stress coordinate system. Three unknown variables arise from using only tensile strength values. Solving a system of three equations derived from the criterion function and using the failure values obtained from destructively testing at three different orientations, the unknown variables as well as the interaction strength components were determined. Results show good agreement for all three materials. Overprediction was found in some instances, attributed to the effect of fiber orientation distribution in the part, and to the complex interactions of the filled structures. To allow a more direct comparison between predicted and experimental data, the resulting failure surface was translated to the global coordinate system (σxx) and compared to the data derived from destructive tensile tests. Good agreement for all materials was observed, with underprediction noted for some orientations, attributed in part to the equation solving method and the nature of the mesostructures of the composites, where interactions between the tows, resin, mold walls, and fibers are present. The results of this work show that the methodology described permits the development of a failure surface for SMC materials when limited data is available. [ABSTRACT FROM AUTHOR]

The mechanical properties of epoxy‐based nanocomposites largely depend on fiber alignment, structure, concentration, and loading condition. To study the influence of these factors on the nonlinear stress‐strain behavior of epoxy nanocomposites, random and aligned carbon nanofiber (CNF)/epoxy composites were fabricated and tested under different strain rates. The elastic modulus and tensile strength were found to be increased as CNF concentrations increased for both random and transversely aligned nanocomposites. This behavior was accurately captured by a three‐dimensional representative volume element (RVE), where the fiber orientation and waviness were modeled from the experimental observation. This RVE predicted the increase in elastic modulus and tensile strength with increase in CNF concentration and strain rate as well as when the CNF alignment changes from transverse to longitudinal. [ABSTRACT FROM AUTHOR]