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Advanced engineering materials like glass fabric-reinforced composites (GFRC) are frequently utilized in automotive components, civil structures, aviation sectors, etc. Contrary to metals, the anisotropic nature of composites makes it difficult to forecast damage and failure under real-time loads. GFRC is employed in this work to demonstrate structural health monitoring (SHM) using a reduced graphene oxide (rGO) coated glass fabric piezo-resistive sensor. The sensor was embedded in the GFRC composite to detect changes in the fractional electrical resistance under flexural strain. The developed composite specimens were subjected to three-point bending to examine the piezo-resistive performance. Throughout testing, the effect of sensor width and relative positions in the thickness direction within the composite specimen on strain and damage detection was assessed. The results of the tests revealed that these parameters were responsively associated with the piezo-resistance of the developed sensor. This study concluded that the developed piezo-resistive sensor has the potential to be used as a strain and damage detection mechanism for glass fabric-reinforced composite structures for disparate applications. [ABSTRACT FROM AUTHOR]

The effects of geometric scaling on the strain rate sensitivity of unidirectional and [+45/−45]s laminates under uniaxial tensile loading has been investigated experimentally. Two material systems, Toray T800/3900-2B carbon/epoxy unitape and Newport NB321/7781 fiberglass/epoxy fabric, were used in the study. The nominal strain rates investigated ranged from quasi-static (0.0002 s−1) to moderate strain rates of 50 s−1 across the scaled specimen geometries. The geometric scaling effects at different strain rates were quantified in terms of the Weibull modulus. At each strain rate, the average failure stress of [0]4 carbon, [0]4 fiberglass, and [±45]s fiberglass showed a declining trend with increasing specimen size. However, the percentage of the strength reduction was less significant at higher strain rates compared to the quasi-static strain rate. In contrast to the other stacking sequences, [+45/−45]s carbon specimens showed a maximum percentage in strength reduction at a high strain rate compared to the quasi-static strain rate, indicating increased scaling effect with strain rate. The magnitude of Weibull modulus (m) for the specimens increased with strain rate indicating diminishing scaling effects, while [+45/−45]s carbon specimens exhibited an opposite trend. [ABSTRACT FROM AUTHOR]

Composite pipe is preferred over metal and other materials for water supply, liquid chemical transport, and fuel and gas transport. This is because composite pipes are more corrosion resistant, have a high strength/density ratio, high stiffness/density ratio, and more durable than metal pipes. The properties of the composite pipes employed may differ based on the operating environment. Therefore, determining the properties of the composite pipe according to the working environment is extremely important for its lifespan. The thickness of the samples is increased in line with different needs (such as increased strength). Increasing the thickness of samples, especially those exposed to different environmental conditions, and investigating the changes that will occur in the physical and mechanical properties of the samples are another important situation. In this investigation, glass fiber (GFRP) reinforced epoxy composite pipes have been examined, which were manufactured using the filament winding method with different layers [±55°]. To determine their properties in different working environments, the GFRP composite pipes were subjected to hydrothermal aging in pure water at 80°C for several days (7, 14, 21, and 28). The changes in their mechanical properties under working conditions were determined through hoop tensile strength tests and low velocity impact tests applied at different energy levels. The experimental results show that the tangential stress values increased by 10.59% as the number of layers increased. As the aging time increased, the durability of the 6-layer composite pipe decreased by 17.69%. Furthermore, the ability of the aged pipes to withstand damage was evaluated, revealing that the aging process exacerbated the damage within the pipes. [ABSTRACT FROM AUTHOR]

Hybridizing the natural fibers with stronger synthetic fibers could significantly improve the properties of the natural fiber-reinforced composites. The improved mechanical capabilities of fiber reinforced polymers result from the fiber's capacity for withstanding a more substantial portion of the mechanical load compared to the matrix it replaces. In order to guarantee the efficient transfer of the mechanical load from the matrix to the reinforcement, it is necessary to incorporate a fibrous filler. Transference takes place when the length of the fiber is longer than a specific critical length. Fibers which are shorter than the critical length will pull out from the matrix when tested to a tensile load. In some cases, complete transfer of the load is not performed. The goal of this study is to learn more about flax (FF), glass (GF), and mixtures of flax and glass (FF + GF) short fiber-reinforced PLA-PBS composites. This is performed to find out how the flax/glass combination affects the mechanical properties of PLA-PBS-reinforced short fiber composites. In order to extend their use for industrial applications, these composites were manufactured via extrusion and, afterward, injection molding. Fiber aspect ratios were followed after compounding and injection processing. The analysis of fiber lengths reveals a noteworthy observation: the proportion of fibers exceeding their critical length of 531 µm and 772 µm for FF and GF, respectively, is more significant when flax fibers (FF) and glass fibers (GF) are combined compared to when they reinforce the composite individually. Specifically, the composite containing both FF and GF exhibits a higher percentage of fibers surpassing their critical length, compared to their individual reinforcement in the composite. The results reveal that 27% of individually extracted single FF exceed their critical length, whereas a higher proportion, at 34%, is observed when FF is part of the composite mixture. In contrast, the critical length is surpassed by only 4% of individually extracted single GF, whereas the combined presence of GF in the composite results in a notably higher percentage, at 19%. The tensile properties of these composites were investigated considering the effect of the hybridization by flax/glass short fibers. It was noted that the tensile properties of the hybrid composites increase comparing to the flax composites from 42.4 MPa to 53 MPa for the tensile strength and from 4.9 GPa to 5.4 GPa for the tensile modulus. In contrast, the elongation at break of the hybrid composites decreases from 1.7% to 1.5% with the incorporation of glass fibers. The experimental results were compared with the predictions of the mixture law and the Cox-Krenchel model. The findings indicate that mixing synthetic fibers with natural fibers is an excellent approach to enhancing mechanical properties. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the mechanical characteristics and application of e-waste as a filler for glass fiber composites made of S and E (e-waste + S E). Metal, printed circuit boards, integrated circuits, diodes, and transistors were separated from the e-waste filler during milling. S and E glass fiber, epoxy, and filler were utilized in proportions of 10%, 10%, and 70%, respectively, on a volume basis. The hand lay-up technique was used to construct composite specimens. Scanning electron microscope analysis was used to gauge how filler loading affected the morphology of composite materials. The composite has a compressive strength of 23.760 MPa, which is 69.71% higher than the Geo poly composite. The tensile strength of this composite is withstood up to 16.078 MPa. It has 53% better tensile properties than Sunflower Husk composites with the same operating conditions. It gives a resistance up to 42 D during hardness test to withstand. It was 15.6% better than the NF30% epoxy composite specimen. The e-waste + S E composite gives a great opposite force of up to 2 kJ on the impact load test.; it was 86.9% higher than fly ash epoxy composites. [ABSTRACT FROM AUTHOR]

This study aims to assess the hybridization effect on the perforation threshold of Low-Velocity Impact (LVI) in thermoplastic glass composite laminates, incorporating layers of resin-impregnated stainless-steel mesh. Reinforcing methodologies such as hybridization are recently being adopted as a practical approach to increasing the energy-absorbing capacity of polymer composites. In the current paper, a multi-step hot press lamination method has been employed to fabricate the hybrid composite laminates strengthened with stainless-steel mesh layers. Several stacking sequences, metal mesh wire sizes, orientation and position relative to the impactor have been examined under various LVI energies. It was revealed that the LVI penetration energy was increased for the thermoplastic-based composite laminates reinforced with stainless-steel mesh layers. Furthermore, the LVI penetration energy threshold was significantly influenced by the metal mesh wire size, orientation and stacking sequence. Finally, the backlight method capability was assessed to detect the after-impact interlaminar damages. [ABSTRACT FROM AUTHOR]

The 3D printing of continuous-fiber composites is currently relevant to engineers and researchers. This study aims to characterize and predict the mechanical properties of Onyx/glass fiber specimens printed using 3D printing. The work assesses the impact of glass fiber printing parameters on the mechanical behavior of printed parts and proposes analytical and numerical methods to predict mechanical properties. A physicochemical analysis was conducted on 3D printed continuous glass fibers. The study also investigated the impact of fiber printing parameters on composite parts. The results indicate that the 3D-printed glass fibers consist of nylon, continuous glass fibers, and voids (porosity), which range from 58% to 63%, 31% to 38%, and 5% to 8%, respectively. Mechanical characterizations indicate that printing fiber layers in blocks results in superior mechanical properties compared to printing alternating layers of glass fibers and Onyx. Additionally, the concentric mode of fiber printing can be challenging if the 'start rotation' parameter is not adjusted correctly. Premature specimen breakage occurred when fiber printing began within their useful length, resulting in a deformation at break that was approximately 34% less, depending on the starting position. The proposed analytical and numerical prediction methods had prediction errors of approximately 7% to 12% and 5% to 7%, respectively. Engineers can use these prediction approaches during the dimensioning phase of 3D printed composite parts. [ABSTRACT FROM AUTHOR]

With the increased use of fibre reinforced composites (FRP), the design of new generation of composite structures with high stiffness and a ductile material behaviour is required to cope with complex load scenarios and high damage tolerances. This can be achieved, in particular, by a combination of conventional fibre-reinforced composites (FRP), which possess high stiffness and strength with metallic materials characterized by their high ductility and associated higher energy absorption capacity. Currently, there are no solutions for hybridisation of high performance filament yarns, metal filament yarns and thermoplastic filament yarns on micro level. Therefore, the main objective of this study is to develop a fibre hybrid composite based on hybrid yarn consisting of glass, steel and polypropylene filament yarns and to compare its tensile and impact properties with those of the composite reinforced only with glass filament yarn. The tensile and impact properties of the unidirectional hybrid composites produced from the developed multi-material hybrid yarn consisting of steel, glass and polypropylene filament yarns are compared with those of a non-hybrid composite reinforced exclusively with glass filament yarn. The results show that by hybridising with steel fibres a characteristic post-failure behaviour can be achieved, so that the developed multi-material hybrid yarns have a high potential for use in composites with high crash and impact performance requirements, where safety demands are essential. [ABSTRACT FROM AUTHOR]

In the present research, glass and basalt fiber-reinforced polypropylene composites' behaviour in quasi-static and dynamic conditions is studied. Composites were fabricated by vacuum assisted Compression molding method. Composites failure under quasi-static tension and compressive conditions was studied along with its failure behaviour under low-velocity impact and super-sonic shock loading under dynamic conditions. The study results showed that basalt fiber-reinforced polypropylene (Basalt/PP) composite's tensile and compressive strength is higher than glass fiber-reinforced polypropylene (Glass/PP). The Basalt/PP showed no penetration against low velocity impact (LVI) with negligible deformations till 50 J. However, the Glass/PP perforated at 50 J with various failure patterns occurring at back side. The fiber-matrix interface adhesion plays an important role in super-sonic shock loading by absorbing shock wave energy due to ductile nature of polypropylene and the two composites absorbed energy via matrix and fibers failure, no brittle failure of laminates occurred under shock loading. [ABSTRACT FROM AUTHOR]

In the present work, a combination of virgin polypropylene and E-glass fiber was subjected to ten (10) reprocessing cycles via extrusion and compression molding techniques to mimic recycling and its impacts on the bending properties of the composites. The samples were characterized using Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), and melt flow index (MFI). The results revealed a gradual depreciation in flexural properties after each reprocessing cycle. The XRD analysis indicated a substantial reduction of peak intensities, degrees of crystallinities, and average crystallite sizes, explaining the lowered flexural properties in addition to a possible reduction in glass fiber lengths (fiber attrition). Melt-processing behavior shows a progressive increase of MFI from 7 to 19.16 g/10 min, confirming the probable damage in molecular weight and loss of complex viscosity. Chemical and structural analysis showed no alteration in the polypropylene major functional groups. It is concluded that the reductions in molecular weight and composites' properties occurred due to chain scission from recycling effects; hence, glass fiber-reinforced polypropylene composites can be recycled only three (3) times unless it is refreshed by the addition of virgin parts to compensate for the lost property. [ABSTRACT FROM AUTHOR]

Hybrid composites are an advanced solution that offers multifunctional capabilities, including exceptional strength-to-weight ratios, vibrational damping and impact absorption. This work describes the damping capacity and flexural behaviour of a hybrid fibrous-particulate system composed of glass/carbon fabrics and three distinct micro-inclusions: silica particles, carbon waste microfibres, and cement. A statistical methodology based on the full factorial design is applied to identify the effects of fibre stacking sequence, including carbon-C5, glass-G5, C2G3, G3C2, GCGCG and CG3C, microparticle inclusions and matrix/fibre volume fraction (40/60 and 60/40) on damping and bending responses. A non-linear finite element (FE) analysis is conducted to explore the stress distribution based on the stacking sequence and predict the failure mechanisms of the hybrid laminate. The results indicate significant interaction effects, with hybrid architectures showcasing approximately 33% higher performance compared to glass fibre composites. A greater dependence on the fibre layup sequence is found for the damping factor, flexural modulus and strength. Notably, the incorporation of silica microparticles leads to an increase in flexural strength. Furthermore, a greater volume fraction of the matrix phase enhances the rheological efficiency in terms of the fibre-particle interface. Carbon fibre layers placed symmetrically on both beam sides (CG3C) and bottom layers (G3C2) significantly enhance the bending performance of hybrid composites. [ABSTRACT FROM AUTHOR]

Continuous glass fiber fabrics can improve the shortcomings of shape memory polymers in terms of mechanical properties. However, the mechanical properties of shape memory composites will not be optimal if the interface between the glass fibers and the matrix is poorly bonded. The purpose of this study is to explore the thermomechanical properties and shape memory behavior of shape memory epoxy resin and composites before and after the chemical modification of glass fiber. The effects of the ratios of epoxy to curing agent and whether the knitting fabrics are modified with silane coupling agent on the properties of the composites are investigated. The results show that the thermal decomposition temperature and glass transition temperature of the shape memory epoxy polymers increase with the increasing mass ratio of diaminodiphenylmethane. The shape fixing ratios and shape recovery ratios of the knitting fabric reinforced composites with different mass contents and silane coupling agent modification are above 98.0% at 18.0% tensile strain. After 10 cycles, the shape memory performance of the composites modified with KH560 is still good. Besides, the addition of silane coupling agent to the composites can reduce the shape recovery time by 17.9% and increase the recovery force with 30.0% subjected to 18.0% tensile strain. The tensile strength of the shape memory composites modified with silane coupling agent can increase 32.8% as compared with that of the composites without modification. [ABSTRACT FROM AUTHOR]

To investigate the fatigue performance of perforated and bolted pultruded Glass Fiber Reinforced Polymer (GFRP) laminates, a series of tests are conducted including static tensile and cyclic fatigue test, while Digital Image Correlation (DIC) and CT tests were implemented to monitor strains around the perforations and damage developed in the samples subjected to tensile and fatigue tests respectively. The stress concentrations of the cyclic loaded perforated GFRP laminates are discussed based on the experiment results. Due to the stress limitation of single bolted laminates, the diameter to width ratio is suggested to be less than 0.3. The GFRP laminates with double holes have a better fatigue performance than that of single hole, which is called the double-hole effect. This effect is also found in double bolted GFRP laminates. Considering the strength of the laminates between the holes and to unify the requirement, the critical distance to width ratio is suggested to be 1.6 and the diameter to width ratio should be less than 0.3. [ABSTRACT FROM AUTHOR]

Detecting the low-velocity impact damage on the FRP composite structures can be challenging because the visible signs on the surface may be subtle. Mitigating the effects of BVID (Barely Visible Impact Damage) is crucial in ensuring the safety and reliability of composite components, especially in industries where these materials are commonly used, such as aerospace and automotive. This article explores the experimental investigations of the impact and post-impact damage propagation under compression in the Graphene Nano-Platelets (GNPs) infused glass fiber epoxy composite laminates. A comparative study of varying the percentage of the nano-platelets (0, 0.25, 0.5, and 0.75%) in the matrix material of the composite laminate is presented. The impact tests at low energies (15 J, 20 J, and 25 J), followed by the quasi-static compression tests, are carried out as per the procedures mentioned in the ASTM D7136/D7137. The digital image correlation technique (DIC) is used to measure strains and plot the strain field on the impacted face of the specimen under compression. Damage envelopes of the impact and compression tests are studied using X-ray CT scans. Micro-level failures are observed through Scanning Electron Microscopy (SEM) to get better insights into the failure mechanism of the composite materials under impact and compression loadings. Upon completing the study, it is found that the addition of the GNP into the matrix materials not only increased the impact performance but also increased the load-carrying capacity of the laminate under compressive loading. A decrement of 2–21% in the energy absorbed in the damage formation is seen with the incorporation of GNPs into composite materials. A maximum increment of 17% in the compressive strength is observed for the composite laminates with the 0.75% GNPs. However, for a particular percentage of the GNP, the compressive strength of the laminate is reduced with an increase in impact energy compared with its virgin counterpart. From X-ray CT scans, it is seen that the laminate under the compression tests fails due to excessive ply-splitting and the delamination at the damage site created during the impact. Fiber breakage, fiber brooming, matrix cracking, fiber-matrix debonding, etc., are some of the other failure modes observed in SEM studies. [ABSTRACT FROM AUTHOR]

Glass Fiber Reinforce Polymer (GFRP) composite Joints were studied under monotonic loads for aerospace and marine applications, but cyclic loading is also a common and serious concern in these applications. In this current study, GFRP composite pin joints were analyzed under cyclic loading, at various geometric factors experimentally and numerically using finite element analysis (FEA) and also compared with monotonic loading. Fatigue tests were carried out using sinusoidal tension-tension loading and covering a range of stress levels from 50% to 90% of effective failure strength (EFS). Weibull distribution was utilized to predict the reliable fatigue life of joints at various joint configurations. Under cyclic loading rapid degradation of dynamic modulus indicated catastrophic failure with shorter fatigue life, while gradual degradation implied slow micro-crack growth and extended fatigue life with progressive failure while in monotonic loading, a sudden fall in the stress-strain curve represented catastrophic failure, and a zigzag curve indicated bearing failure mode before fracture. The damage rate was also determined from the hysteresis loop cycles which indicate greater loop expansion due to the stiffness degradation and higher energy dissipation shows rapid damage accumulation and shorter fatigue life at higher stress level. On the other hand at lower stress level, moderate enlargement of the hysteresis loop demonstrates extended fatigue life with slower damage propagation. [ABSTRACT FROM AUTHOR]

This study is dedicated to conducting a comprehensive examination, both experimentally and numerically, to characterize the mechanical properties of a composite material composed of Alfa fibres and unsaturated polyester resin. In pursuit of this objective, we diligently prepared composite specimens in accordance with the ASTM D3379-75 standardization. The Alfa fibres used were prepares using a purely natural-based extraction technique, which retains approximately 78% of the composite's performance achieved through chemical treatment. The resulting composite consists of polyester resin reinforced with varying weight fractions of fibres, ranging from 0 to 18%.The test results of the manufactured bio-composite show that specimens with an 18% weight fraction offer a tensile strength of 49.749 MPa, whereas specimens with a 10% weight fraction exhibit a strength of 44.312 MPa. Additionally, the specimens with 18% fibre reinforcement exhibit a net increase in Young's modulus by 46% compared to the fibre-free composite, with Young's modulus ranging from 1469.66 MPa to 2726 MPa. When compared with composites based on fibre glass, the introduced bio-composite with 18% Alfa fibres exhibits similar stiffness to that of glass fibres. Additionally, the outcomes from the Finite Element Model (FEM) reveal a remarkable agreement with the experimental data, underscoring the practical applicability of the proposed methodology and tools for accurately simulating tensile tests in composite structures. [ABSTRACT FROM AUTHOR]

The meso-structure of woven fabrics plays a pivotal role in enabling significant deformations. To precisely characterize the deformation behavior of woven fabrics, a mesoscale model based on their meso-structure is developed. In this model, the fiber yarn is represented as a Timoshenko beam with fluctuations described by the shape function. A novel approach is proposed to establish the relationship between the macroscopic mechanical response and the infinitesimal strain of the beam, employing the principle of virtual work. The shearing behavior of woven fabrics is characterized by considering friction energy dissipation and transverse compression among fiber yarns. The general applicability of the proposed model is validated through its application to glass fiber woven fabrics and jute fiber woven fabrics. The model parameters are determined through uniaxial tensile and bias-extension experiments. The accuracy of the model is verified using bias-extension and picture frame experiments. The results demonstrate that the proposed model can effectively simulate the large deformation of woven fabrics. [ABSTRACT FROM AUTHOR]

The vacuum bagging is a common but critical step of various manufacturing process chains for Carbon/Glass Fibre reinforced polymers (C/GFRP). Whilst developing a new generation of vacuum bagging, significant efforts have been made to deeply understand the relevant physics fields, process variables involved and to provide predictive approaches to support dimensioning and scaling exercises prior to implementation into real production process. Main features of the new bagging system are, (1) the reduction of material diversity through merging of various properties within one single layer and, (2) the suppression of critical folding steps by using thermoforming for pre-shaping purposes. This paper will mainly focus on considerations of heat transfer during the pre-shaping of the film, directly on the CFRP part short before the curing step. For the better risk assessment of the short time exposition of an uncured composite part to the heat flow, a problem of transient coupled field analysis involving heat transfer via conduction, convection and radiation is formulated and solved by using Finite Element Analysis in COMSOL under consideration of realistic process conditions. Further a section dedicated to the comparison of the obtained results with measurements performed on a system including an IR-emitter, the bagging material, a ground plate and in some studies as well a CFRP sample is included. During the study the influence of time, power output of the emitter, distance between emitter and surface as well as irradiation angle has been assessed including a comparison of simulated results and performed measurements. [ABSTRACT FROM AUTHOR]

Resin pre-coating technology is widely used in all aspects of composite materials, especially in the repair of composite materials. The pre-coating is formed by combining acetone with the resin, which is diffused and cured by the epoxy adhesive at the same time. It acts as an interlock to prevent the interface from debonding and to fill in the damaged cracks. The capillary action of acetone allows the resin to permeate the cracks in the fiber damage layers, thus filling the cracks and completing the repair. The pre-coating solutions of 10 wt%, 20 wt%, 25 wt%, 35 wt%, and 45 wt% resin were applied to damaged areas respectively, and cured at 60°C for 7 days. The crack filling effect was observed by scanning electronic microscopy (SEM). At the same concentration, the effect of prolonged repair time was also studied. The other two repair times were 14 days and 30 days respectively. In addition, the tensile properties of the materials before and after repair were tested and compared. The results showed that 25 wt% resin pre-coating had the best repair performance after 7 days, with a repair rate of 27%, which was 22% higher than the conventional repair without resin pre-coating. However, the repair effect became more obvious after the extension of repair time, and the repair effect of 25 wt% resin pre-coating reached 44% after 30 days curing. Therefore, it was found that the resin can fully penetrate the cracks in the damaged area with resin pre-coating technology, and 25 wt% resin pre-coating solution is the best choice. [ABSTRACT FROM AUTHOR]

In this research work, the effect of various environments on the impact properties of fiber metal laminates was investigated. To do so, in the first step, the 2024 aluminum layers were surface modified with the etching method. Then, the various glass fibers/epoxy composites with the configurations of (0°/0°/0°/0°, 90°/90°/90°/90°, +45°/−45°/−45°/+45° and 0°/90°/90°/0°) were sandwiched between two aluminum sheets. In the following, these samples were aged under thermal cycling (between 25 and 100 °C), isothermal aging at the temperature of 100°C, cryogenic cycling (between −196 and 25 °C), and cryogenic isothermal aging at the temperature of −196°C. To understand the effect of various aging methods on the mechanical features of these structures, the Charpy impact test was performed. Also, the failure mechanisms and related phenomena were assessed by visual observations and microstructural investigations. In the first steps of thermal aging, the impact strength of FMLs was improved, which the highest of that being 46.9%. In the higher cycles or exposing times, the impact strength showed reducing trends, due to thermal degradations of the epoxy matrix. The cryogenic cycling in the high cycles reduced the impact strength of FMLs. But in the cryogenic isothermal condition, in some cases, the improvement in the impact strength was seen, which the highest of that being about 43.4%. [ABSTRACT FROM AUTHOR]

An experimental study was performed to investigate damage sensing and fracture toughness of multifunctional conductive glass fiber composites under dynamic mode-I fracture loading. Carbon nanotubes (CNTs) were dispersed within the epoxy matrix using a shear mixing and sonicating process. An electrostatic wet flocking process was used to reinforce milled short PAN-based carbon fibers onto each of the layers of glass fiber fabric along the thickness direction in the composites. These layers of flocked fabric were stacked, and a vacuum infusion process was employed to fabricate the composites. The parametric study consisted of two carbon fiber lengths (80 μm and 150 μm) and two fiber densities (1000 fibers/mm2 and 2000 fibers/mm2) and was performed to investigate the damage sensing capabilities of a three-dimensional conductive network generated through CNTs and carbon fibers. A double cantilever beam (DCB) configuration was considered, and a modified Hopkinson pressure bar setup along with a high-speed camera was used to investigate dynamic fracture toughness of the composites. The piezo-resistance response of the composites during dynamic fracture was measured using a modified system of four probes. For comparison, composites were also characterized for fracture toughness and piezo-resistance under quasi-static fracture loading conditions. The addition of short, milled PAN-based carbon fibers significantly increased the fracture toughness of glass/epoxy composites. The piezo-resistance response of the composites was easily correlated with instances of sudden crack growth during static fracture loading. [ABSTRACT FROM AUTHOR]

Interest has grown in recent time on the development of three-component polymer nanocomposite with enhanced properties. However, the study focuses on the effect of TiO2 nanofiller on the mechanical, tribological, dielectric, and corrosion resistance properties of boron-free glass fiber (BGF) reinforced polyimide (PI) composite produced with spark plasma sintering route. Microstructure of the samples was examined using scanning electron microscopy. Mechanical, tribological, dielectric, thermal, and corrosion behaviour of the samples were characterized by nanoindenter, ball-on-disc, LCR meter, TGA, and potentiodynamic polarization test, respectively. The SEM results show that the introduction of the nanoparticles into the BGF/PI composite aids in more uniform distribution of the BGF particles within the PI matrix, and thus good interfacial interaction of the glass fiber and the PI matrix structure. Comparing the BGF/PI composite sample with BGF/TiO2/PI nanocomposite, it was observed that the nanocomposite depicted better hardness, elastic modulus, low friction coefficient and wear rate, dielectric, and enhanced corrosion properties. With TiO2 additions, hardness and modulus of the PI composite was improved by 56.6% and 10.1%, respectively. In addition, PI composites filled with TiO2 depicted a 0.07 coefficient of friction and wear rate of about 67.7% in reduction than that of neat PI and 9.0% in reduction than that of the pristine BGF/PI composites. Improved interactions between the reinforcements and the host matrix are suggested as the possible mechanism resulting to the desirable properties of the three-component PI nanocomposite recorded. Finally, the developed nanocomposite is suggested to be favourable for automobile, aerospace, and microelectronic device applications. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the axial compression behaviour of perforated glass fibre reinforced plastic (GFRP) circular tubes. A total of 12 GFRP medium-length tubes with and without circular holes were tested under axial compression. The influence of hole size and hole quantity on the failure mode and mechanical behaviour of perforated GFRP tubes were carefully evaluated. The overall buckling failure and material strength failure, mainly determined by the hole size, were observed in the axial compression tests. The critical load and axial stiffness of the perforated tubes decreased further with the increase of hole sizes and quantities, compared to those of the intact GFRP tubes. To reveal the damage mechanism of perforated GFRP tubes, three-dimensional digital image correlation (3D-DIC) technique was used to analyse the evolution of full-field strain around the hole. It was demonstrated that the damage mechanisms of the overall buckling failure and material strength failure were respectively compression-shear destruction and tension-shear destruction in the high strain concentration regions around the hole. Finally, design-oriented equations were proposed to predict the critical load and axial stiffness of perforated GFRP tubes under axial compression, and 95% confidence interval was used for interval estimation. The proposed equations were in good agreement with the test results. In addition, the prediction results of axial stiffness are generally more accurate than that of critical load. [ABSTRACT FROM AUTHOR]

The effect of low-velocity impact loading and seawater aging on the residual bending properties of glass fiber reinforced polymers (GFRPs) was evaluated. The self-sensing capability of the composite laminates provided by a hybrid combination of multiwall carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) was also examined. The composite laminates were fabricated by RTM with the incorporation of different contents of MWCNTs and GNPs onto the glass fiber surface using the spray coating technique. Impact tests were performed on specimens with and without seawater (SW) aging and then bending specimens were taken to evaluate the after-impact bending behavior. An important reduction in mechanical properties of composite laminates produced by SW aging, caused by plasticization and swelling effects of the polymer matrix, was confirmed. Despite this physical degradation in the mechanical behavior of GFRP composites, a positive synergistic effect of the carbon nanostructures (CNSs) in the composite laminates was observed. Carbon nanofillers cause the maximum force during the impact test increase in comparison with neat specimens; this effect was exhibited by both samples, with and without seawater aging. Previous impact damage reduced flexural strength and flexural modulus of dry (14% and 43%, respectively) and wet samples (15% and 26%, respectively); however, the reduction in flexural strength is slightly smaller in a certain hybrid combination of CNSs. Another important finding was that the self-sensing capability of GFRPs with CNSs was preserved, even after the impact loading and even after the seawater aging, making this technique suitable for structural health monitoring of marine components. [ABSTRACT FROM AUTHOR]

Thermoplastic composite materials are being increasingly used in many domains, such as automotive, marine and aeronautics. This growing interest is due to the relatively good mechanical properties and the recycle-ability of these materials. In various heat assisted forming technologies, thermoplastic composites may be subjected to severe conditions such as high temperatures, complex strain paths and potentially significant strain rates. This is expected to highly influence the overall behavior of these materials and make the characterization of their mechanical behavior more complicated. In this paper, the mechanical behavior of discontinuous glass fiber reinforced polypropylene composite is investigated at temperatures going from room temperature (RT) to 120°C and strain rates ranging from quasi-static conditions to 10 s −1 by means of uniaxial tensile tests. The effect of material orientation is also investigated at RT and quasi-static strain rate of 0.001 s −1 pointing out a clear anisotropic behavior. The tensile properties including Young's modulus E, ultimate tensile strength σ ult and strain at failure ɛ f are determined based on the Standard ISO-527 reporting an obvious sensitivity of the material to temperature and strain rate. Based on literature review, the phenomenological isotropic constitutive model of G'Sell and Jonas, originally designed for unreinforced semi-crystalline polymers, is selected to describe the mechanical behavior of the studied material. A modification of the original constitutive equation is proposed for a better representation of the overall behavior of the material at different temperature and strain rate conditions. Finally, the validity of this phenomenological law calibrated by means of the uniaxial tests, is evaluated for an equi-biaxial loading state close to that encountered by the material during heat assisted sheet forming process. The significant disagreement highlighted between numerical and experimental results proved that the uniaxial tensile tests are not sufficient to characterize the behavior of the material when a complex loading condition is imposed. [ABSTRACT FROM AUTHOR]

Understanding the thermoforming process for thermoplastic composites is of great importance to ensure the quality of the composite product but is difficult because of the complex material constitutive models and thermo-mechanical coupling in the thermoforming process. In this study, a woven fabric thermoplastic composite consisting of glass fiber and polyetherimide resin was thermoformed under one-sided cooling conditions. After the effective material properties are homogenized with newly developed, two-step asymptotic homogenization methods, and the temperature and pressure boundary conditions are measured experimentally, a 3D composite laminate sandwiched by interfacial layers and metal molds was finite element simulated in the macroscale. The simulated warpage, which was caused by the in-plane residual stresses, was consistent with the experimental results when reasonable tool–part interactions were considered. Subsequently, the temperature, displacement, strain, and stress were comprehensively discussed in terms of their spatial distribution, temporal evolution, and correlations with the others. [ABSTRACT FROM AUTHOR]

A method is proposed to locally heat areas of thick (>25.4 mm) continuous glass fiber reinforced thermoplastic (C-FRTP) composites with embedded wire mesh resistive heating elements. Four test specimens including 10.6 cm wide nichrome mesh heating elements embedded in C-FRTP laminates were fabricated and used for heating trials, showing that the composite can be locally heated to near the thermoplastic forming temperature over its entire thickness in less than 1 hour. The heating trials were simulated using a purpose-built finite difference model to investigate detailed temperature distributions. The simulations show that the internal resistive heating elements are capable of locally increasing the temperature of the composite with negligible effect on the adjacent material. Heating efficiency is between 73% and 77%, with temperature differences in the z -direction at peak temperatures less than 35°C. Temperature uniformity can be improved by longer heating times and more heating elements. The local heating method does not cause deconsolidation of the part. The heating method was also experimentally assessed on a more complex cross-section laminate with varying thickness and a foam core using stainless steel mesh heating elements. Results from the first heating tests were applied to the experimental assessment of the more complex laminate to reduce z -direction temperature differences. Numerical simulation of the heating of the foam core laminate showed a z -direction temperature range of 15.5°C. The results of this study show that embedded resistive heating is a cost-effective and simple method for heating a local portion of a thick fiber reinforced thermoplastic composite. [ABSTRACT FROM AUTHOR]

Polymer composites have remarkable popularity in the aerospace and automotive industries due to their high strength-to-weight ratio and ease of production. In this study, the effects of the glass fiber (GF) and maleic anhydride grafted polypropylene (PP-g-MA) as coupling agent on mechanical properties, shrinkage and warpage of polypropylene (PP) were investigated. Tensile, flexural, shrinkage and warpage tests were performed according to relevant standards. Results indicate that the strengths and moduli of composite specimens have been significantly improved compared to pure PP. Also, the shrinkage and warpage of composite specimens were reduced. Analysis of variance showed that both GF and PP-g-MA had a significant effect. In composite with a 40% weight fraction of GF, the tensile and flexural strengths were increased by 91% and 62%, respectively. A micromechanics model was proposed to predict the tensile modulus of composites. A good agreement between experiments and the model was achieved. [ABSTRACT FROM AUTHOR]

When a composite laminate is subjected to humidity, moisture diffusion occurs depending on the number and thickness of the lamina. Water diffusion changes the mechanical response of laminates and usually causes a significant reduction of the mechanical properties of the composite specimens in ocean structures. One of the most important mechanical properties of laminates is flexural stiffness which should be considered in the design procedure. Despite the extensive research on single cycle aging of composites, cyclic aging of these materials is less explored. The aim of the current research is to investigate the variation of mechanical properties of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composites as a substrate in adhesive joints with the same initial flexural stiffness values subjected to cyclic wet/dry aging conditions for long-term structural applications. The matrix used in the CFRP and GFRP composites are based on epoxy and vinyl ester, respectively. Both unaged and cyclically aged samples were characterized by tensile and three-point bending tests. In order to simulate the moisture absorption condition of composites in adhesive joints, one side of the composite laminates was sealed with aluminum foils and three sides were exposed to humidity. The interaction between the composite thickness and the number of aging cycles was also investigated. The experimental results show that in cyclic aging condition, the reduction of flexural stiffness in CFRP is more than GFRP laminates and GFRP laminates is more suitable for ocean applications. [ABSTRACT FROM AUTHOR]

In this study, a series of experiments and finite element analyses were conducted to investigate the effects of glass fiber sheet (GFS) lamination on the strength of pin-bearing single-bolted pultruded glass-fiber-reinforced polymer (PGFRP) connections. In the experiments, nine types of GFS lamination were molded using the vacuum-assisted resin transfer molding method (VaRTM) and bonded onto the surfaces of PGFRP members. Then, four different end distances of PGFRP plates to bolt diameters (e / d) were surveyed, ranging from 3 to 6. The results indicated that all types of GFS lamination offered excellent improvement effects for the ultimate loads of the PGFRP connections. The strengthening effects were better when the connections had smaller e / d values. In addition, external 0°/90° GFSs provided the best performance for GFS-strengthened PGFRP connections with medium e / d values. Finally, it was demonstrated that finite element analysis (FEA) could be a useful method for predicting the failure loads of GFS-strengthened PGFRP connections. [ABSTRACT FROM AUTHOR]

The mechanical properties of composites produced without additives are limited by the matrix and fibers of constructed material. To increase the mechanical properties, micro or nano size particles can be added to the composite. In this study, A l 2 O 3 particles with a purity of 98% and a size of 0–50 μm were added to the epoxy material in the ratios of 1%, 2%, 3%, 4% and 5% by weight to optimize the parameter in order to enhance the mechanical properties of [110P/163 T/195T]s stacking sequenced woven composites. Tensile fatigue tests were performed with a computer-controlled fatigue test device with a 100 kN load cell, by applying R = 0.1 load ratio, 6 Hz frequency, and sine wave load form. Fatigue tests were conducted at different load levels. As a result, increase between 119%-2441% was observed in the fatigue cycle of micro- A l 2 O 3 reinforced woven composite materials compared to non-particles added epoxy woven composites. The highest damping rate was observed as 57.528 in 1% micro- A l 2 O 3 , and the lowest damping rate was observed as 26.312 in composite with no Al2O3 particles. The micro-structure morphologies of micro-Al2O3 reinforced woven composites were observed by SEM. [ABSTRACT FROM AUTHOR]

In this work, a fifth-order shear deformation theory is computed using the layer-wise model to determine non-dimensional fundamental frequencies. The theoretical, experimental, and finite element analysis (FEA) results are compared for a standard isotropic material. Hand layup technique is used to prepare glass fiber reinforced polymer composites (GFRPC) with selective layers filled with graphene and flyash. This technique helps to reduce the fabrication cost as the whole structure is not to be strengthened by the fillers. Six classes of the laminated-composite-plate (LCP) such as outer layer graphenated LCP (O-LCP), core layer graphenated LCP(C-LCP), functionally graded LCP (FG-LCP), LCPs only rich in graphene (G-LCP), LCPs only rich in flyash (F-LCP) along with a neat epoxy-glass LCP (N-LCP) are fabricated. A low-cost frequency measurement module is set-up to measure the fundamental frequency (FF) of the fabricated LCPs. FFs, amplitudes, non-dimensional stress parameters, and central deflection of the LCPs under harmonic load, the buckling strength, and displacements of the LCPs are calculated. It is found that harmonically excited C-LCP and O-LCP have better stability accompanied by lower deflections, followed by G-LCP as compared to other kinds of LCPs. Also, the addition of graphene increases the buckling strength of LCPs, which portrays that the local layer filling is a useful technique to enhance the strength of the LCPs. [ABSTRACT FROM AUTHOR]

The fire-retardant properties of high-performance fiber-reinforced composites are the crucial benchmark for composite structure stability. However, in the current flame-retardant solution for composites it is difficult to reach the balance between fire resistance and structural performance due to the deteriorating composite interface. In this work, the carbon fiber-reinforced composite was covered with functional glass fiber layers, in which the glass fiber veil had been treated with flame-retardant agents and silicone-modified waterborne polyurethane, in order to be endowed with flame-retardant capability and structure toughness. As such, a significant improvement in the flame retardancy and mechanical structure of the composites could be observed. When compared with the control, the total heat release and total smoke release for composites with 8% silicone-modified waterborne polyurethane treatment could be decreased by 18.5% and 18.1%, while the tensile and flexural strength were significantly increased by 47.3% and 62.2%, respectively. This well-balanced performance is attributable to the structure design with a toughened glass fiber veil to protect the composite surfaces from fire combustion and structure failure. Therefore, this flame-retardant structure design provides a new strategy to achieve high-performance composites with prospective applications for aircraft and aerospace. [ABSTRACT FROM AUTHOR]

With industrialization and population growth, solid waste management has become a universal challenge. The destination and incorrect storage of the waste from quarries have become a recurring problem caused by the extraction of mineral resources. The possibility of use for this waste, to minimize its impacts, is the creation of new products that can be useful to engineering using stone powder. Therefore, this study aims to create a new composite using limestone powder with different granulometry to analyze the influence that its insertion and the grain size can cause in these materials. The produced laminates were submitted to uniaxial tensile tests under the norm ASTM D 3039 and volumetric density ASTM D 792, The modifications that occurred in the properties of the specimens were studied in detail, obtaining results that show that the insertion of limestone powder provides the material with new mechanical characteristics, such as the rigidity increase. Among the produced composites, the one that had received limestone as obtained presented the best performance, increasing 9.33% of its elasticity modulus in comparison to the original. [ABSTRACT FROM AUTHOR]

A comprehensive experimental investigation is performed to understand the damage sensing capabilities of thermoplastic intra-ply carbon/glass laminated composites embedded with Carbon Nanotubes (CNTs) under quasi-static interlaminar shear and mode-I fracture loading conditions. CNTs are dispersed in thermoplastic Elium® resin using a combination of ultrasonication and shear mixing processes. This resin mix is used in a vacuum infusion process to fabricate four different intra-ply laminated composites orientations; G-0-C-90 [Carbon fibers are in the longitudinal direction], G-90-C-0 [Glass fibers are in the longitudinal direction], G-45-C-45(R) [carbon and glass fibers are at +45°, and −45° from the longitudinal direction and form a repeating layup], and G-45-C-45(A) [carbon and glass fibers are at +45°, and −45°, but with alternating directions for each lamina in the layup]. Four-circumferential probes are utilized to obtain the piezo-resistance measurements associated with damage inside the composites under shear and mode-I loadings. In the shear experimentation, the G-45-C-45(A) orientation demonstrated the largest interlaminar shear strength, at 50% greater than the G-45-C-45(R) orientation. Both G-45-C-45(A) and G-45-C-45(R) had significantly larger shear strains compared to the G-90-C-0 and G-0-C-90 orientations. However, the best resolution in shear damage sensing was seen with the G-0-C-90 composites. In the mode-I fracture experiments, the greatest fracture initiation toughness is shown with the G-0-C-90 orientation, which is 80% greater than the G-90-C-0 orientation. Compared to all orientations, the G-0-C-90 orientation also provided the most sensitive electrical response. [ABSTRACT FROM AUTHOR]

The aim of this study is to produce curved sandwich composites with different arrays by adding Ethylene Propylene Diene Monomer (EPDM) rubber interlayers between glass fiber woven fabrics and to investigate their behaviours under low-velocity impact. For this purpose, sandwich plates were produced through the vacuum infusion method by using glass fiber and rubber layers on the steel mold manufactured in curved form. Impact tests were applied on the plates and the effect of the stacking sequence for glass fibers/rubber layer on the impact energy absorption was examined. The energy absorption property of the composites was improved by a maximum of 45% with a layer epdm used in the midplane of the composite. Also, when rubber layers were used on the outermost surface of the composites, the damage area reduced by 14%. In the numerical part, the tests were modelled using LS-DYNA finite element packaged programme and the Hashin failure criterion-based material model was used in order to view any damages on the composite structure after the tests. The agreement between numerical and experimental results was obtained with a maximum error of 19% [ABSTRACT FROM AUTHOR]

A novel marine composite structure (experimental tidal turbine blade) made up of a polyurethane (PU) foam/glass fiber/epoxy resin composite with multiwall carbon nanotubes (MWCNTs) is proposed herein to self-sense its strain under a structural test scenario. To achieve this, MWCNTs were deposited onto glass fiber fabric by spray-coating technique in order to form an effective electrical percolation network onto the external skin surface of the tidal turbine blade which enables piezoresistive capability. After MWCNT deposition, the blade was manufactured by means of one-shot resin transfer molding (RTM) in a closed and heated metallic mold specially designed with a blade geometry of 67 cm length. The results confirm that the spray coating technique is a viable method to deposit MWCNTs onto glass fiber surface and form electrical networks into the blade at a relatively low MWCNT concentration. Finite element analysis (FEA) predicted a suitable structural blade design with a maximum failure index value of 0.9 attained in the blade shear web. The measured longitudinal strains of the tidal turbine blade were in good agreement with the numerical strain values predicted with FEA. Electromechanical tests carried out on a structural test rig designed and instrumented for tidal turbine blades showed that the electrical resistance change response of carbon nanotube (CNT) network integrated into the blade was capable of following the mechanical curve response up to the blade limit load, confirming its ability to self-sense its strain in real time. [ABSTRACT FROM AUTHOR]

The field of application of Glass Fiber Reinforced Polymer expands as well as the size of the component where composite material is applied. Due to the size limitation of the prepreg used, it is difficult to apply 1ply to large parts. Many studies have been reported on the bolt joint that assembles parts and parts for the joint area, butt and overlap design for joining dissimilar materials, and mechanical properties. Although the mechanical properties of the joint areas are important, studies on the microstructure are also needed. In this study, the microstructure was observed by controlling the type of subsidiary materials in the bagging process by applying prepregs of the same composition. It was found that the air and resin flow inside the prepreg acted differently depending on the type of subsidiary material. The flow of resin during curing was inferred from the influence of subsidiary materials and explained by connecting it with the microstructure. The behavior of the resin determined thickness, resin, and void contents of the composite. This flow affects voids in the joint area, causing differences in microstructure and mechanical properties. There was no significant difference in the tensile strength of the laminate specimens manufactured according to the process, but the minimum strength was found in the specimens containing many void contents. The joint specimen showed a decrease in strength as the void content increased. It was discussed that this reduced the adhesive force of the specimen due to the effect of the void generated in the joint area. [ABSTRACT FROM AUTHOR]

The impact property and residual flexural property of three-dimensional (3D) five-directional braided carbon/glass hybrid epoxy composites were studied. Four kinds of arrangement for carbon fiber and glass fiber in the axial yarn were designed. Taking pure carbon fiber composites (C/Ca) as the control, the rest of arrangements were that glass fiber and carbon fiber alternately arranged at the width direction (C/G1), glass fiber and carbon fiber alternately arranged at the thickness direction (C/G2), and only glass fiber appeared at the axial yarn (C/G3). Results showed that the C/G2 composite has higher impact energy absorption capacity, and the C/G1 composite has higher impact stress. The flexural properties of C/Ca composite are the best and that of C/G3 composite are the worst before impacting. This study is helpful for the structural design of composites in specific occasions. [ABSTRACT FROM AUTHOR]

The purpose of this research is to make a nanocomposite with combined fibers in order to achieve two integrated mechanical characters including strength and plastic deformation in an optimal way. Novalac type phenolic resin (PF), short fibers carbon (CF) and glass (GF) and silica (SiO2) nanoparticles were used for making. The results showed that with the hybrid of carbon and glass fibers (CGF) in the composite, the ultimate strength and Plastic deformation increased compared to the samples without a combination, and it was modified as an optimal sample. Also, the results showed that the composite sample with hybrid fibers with 2 wt% SiO2 nanoparticles increased the tensile strength by 25%, the bending strength by 48% and the buckling strength by 37%. From the X-ray diffraction and EDX tests, the dispersion of nanoparticles in the composite was determined, and the SEM images showed that with the presence of SiO2 nanoparticles, The amount of adhesion and penetration between resin and fibers has increased. One of the main applications of hybrid nanocomposite can be mentioned portable light structures on land, sea and air, sports goods and orthopedic equipment. [ABSTRACT FROM AUTHOR]

Wind power is rapidly expanding worldwide, and so is the installation of wind turbines. The concept of wind power as a clean-energy alternative will be questioned if the waste from these turbines is not and adequately controlled. The goal of this review paper is to evaluate the various approaches for end-of-life management of wind turbine blades emphasizing on fibre recovery. Different methods for recovering carbon and glass fibres are described, including thermal treatment and chemical treatments and their economic and environmental comparisons. Life cycle assessment and comparative analysis of different recycling processes are also presented. Natural composites, modified thermoset composites, and thermoplastic composites are also covered as alternative environmentally friendly blade materials. [ABSTRACT FROM AUTHOR]

In this experimental study, hybrid composite properties for hydrokinetic turbine blades were determined, and its performance was examined. The reinforcements included glass fiber, treated and untreated highland bamboo fiber, reinforced polyester-based composites and their hybrid composites, as well as row bamboo (bamboo culm). The row bamboo was prepared on the bamboo culm's outer surface to get rid of any leftovers, before cutting in accordance with the specimen test standards. In order to make hybrid composite materials, polyester resin was mixed with fibers in the proportions of bamboo fiber/glass fiber (50%/50%), and fiber/matrix (30%/70%). The composite containing glass fiber has a flexural strength that is 12% and 21% higher than materials reinforced with alkali-treated and untreated highland bamboo fiber reinforced composites respectively. The alkali treatment of highland bamboo fiber improved its physical-mechanical properties, making it suitable for use different application. Alkaline treatment boosts the composite's tensile and compressive strength by 37% and 3.4% for composite reinforced with untreated bamboo fiber, and 10.2% and 23.8% for composite reinforced with glass fiber, respectively. The fiber density of highland bamboo was increased by removing less dense non-cellulosic components (hemicellulose and lignin). However, the fiber's moisture absorption is the main issue in using it in a composite that works submerged in water. This study investigated whether incorporating glass fiber in highland bamboo-glass fiber polyester hybrid composite reduces the composite material's water uptake. A reduction was found, however, the density was increased. It is challenging to employ row bamboo for the construction of hydrokinetic turbine blades as water ingress of the compositemust be avoided even in the presence of erosion caused by cavitation and impact with foreign bodies in the water. [ABSTRACT FROM AUTHOR]

In this study, cold atmospheric pressure plasma jet was adopted to glass fibers surface modification with tetraethyl orthosilicate as a precursor. To enhance the interfacial bonding forces of glass fiber reinforced polypropylene (GFRP) composites, SiOx nanoparticles were polymerized on the fiber surfaces. The effect of two factors (the distance between nozzle and fiber (D) and the treatment time (T)) on the interfacial bonding behavior of GFRP composites was studied. The modified fibers and composites properties, including surface topography, chemical composition, wettability and interfacial mechanical properties, were studied comprehensively. The optimal parameters were obtained at D = 17 mm and T = 12 s. Our results indicated that the interlaminar shear strength of GFRP composites was increased by 30.79% compared to control group. Further studies found that plasma treatment introduced larger surface roughness, surface energy and more oxygen-containing functional groups, which was responsible for the interlaminar shear strength improvement. [ABSTRACT FROM AUTHOR]

Process-induced surface waviness effects represent a major concern for series production of high-quality lightweight structures based on fiber reinforced plastics (FRP). This paper suggests a method for the numerical prediction of these effects by using the example of processing glass fiber reinforced plastics (GFRP) in a resin transfer molding (RTM) process. The influence of reaction kinetics, chemical shrinkage and cure-dependent viscoelastic properties of the resin are taken into account. Furthermore, the dependence of surface quality on curing cycle, consolidation pressure, textile architecture and thickness of neat resin layer (NRL) at the part surface are investigated. The work is based on published material data and a visco-thermo-elastic simulation approach which has been previously presented and validated. All numerical results are compared to the surfaces of FRP plates that were manufactured with the corresponding parameter variations. Based on a literature survey, different surface waviness values have been identified for comparison of experimental and numerical results. Satisfactory agreement between experiments and simulations is found. Furthermore, it is shown that the analyzed NRL thickness has no relevant influence on the surface waviness while the curing temperature significantly affects the surface waviness. The role of relaxation-induced change of the surface waviness is highlighted by performing long-term measurements and corresponding time-dependent simulations. It is concluded that relaxation plays a decisive role in the appropriate selection of the subsequent surface finishing process. The suggested simulation approach provides a basis for optimization strategies to improve surface quality and reduce post-processing effort. [ABSTRACT FROM AUTHOR]

Mechanical properties considerably reduce in wood-plastic composites (WPCs) due to the use of wood particles, so the structural applications of these composites are scarce. Thus, embedding continuous fibers is considered the most reliable method for increasing mechanical properties, although there are still challenges in employing this method on a large scale. In this study, an elaborated, special modular die with the capability of adjusting 14 rovings of continuous fibers was designed, manufactured, and implemented to simultaneously embed continuous glass fibers into the extruded WPC profile. More precisely, it was aimed to investigate the arrangement of fiber rovings into the desired positions in a WPC profile of 70 wt% wood content. Also, the effect of the glass bundle tex (at three level, 1200,2400 and 4800) and the fiber position (at four levels, 0, 2, 4, and 6 mm of relative movement of the guides) on the mechanical properties of WPCs was evaluated. According to the results, the flexural strength of reinforced specimens for 1200, 2400, and 4800 texes increased by 85.8, 107, and 159.7%, respectively, compared with the non-reinforced composite. Theoretical values were calculated and compared with experimental outcomes. Based on the results, The failure mode was non-catastrophic, which means the specimens were able to carry partial loading; a desirable characteristic for the structural applications. [ABSTRACT FROM AUTHOR]

In this work, we investigate toughening mechanisms in soft polymers reinforced with stiff fibers, particularly focusing on the effect of the strength of the fiber-matrix bond on the toughness. We print polydimethylsiloxane with short milled glass fibers using direct ink writing, an extrusion-based 3D printing method. This process produces composites with aligned fibers. Fibers can be treated with acid prior to printing, which improves the strength of the fiber-matrix bond. This results in higher yield stress and toughness. The higher toughness of the composites can be attributed to intrinsic mechanisms such as matrix deformation and fiber pullout, as well as to extrinsic mechanisms like mechanical dissipation. The intrinsic toughness of the composites is analytically estimated using a micro-mechanical model and experimentally measured by stretching the composites in the direction of fiber alignment. Finally, we demonstrate partial healing of the fiber-matrix bond after initial pre-stretch. Thermal treatment of the damaged composites results in partial recovery of stiffness and toughness. [ABSTRACT FROM AUTHOR]

In the present work, the low-velocity impact characteristics of the spherical core sandwich structures made of glass fibre reinforced plastic (GFRP) are tested at different strike velocities (3, 5, and 7 m/s). Four different types of core orientation, namely, regular, interlock, inverted, and stagger, are designed and fabricated by the hand-layup method. Vinyl ester resin and woven glass fibre fabrics are used as matrices and reinforcements, respectively. The diameter of the spherical core and the pitch distance is chosen as 16 mm and 32 mm, respectively. The impact behaviour of the novel spherical sandwich structures is examined based on the maximum contact force, energy absorption capacity, coefficient of restitution (COR), and damage behaviour. The Regular model shows enhanced energy absorption capacity with a specific absorbed energy of 0.092 J/(kg/m3) at 7 m/s impact velocity. Similarly the Interlock model shows good damage resistance. The typical failure patterns observed in the Interlock model at 3 m/s are matrix cracking (MC) and fibre breakage (FB), whereas, at 5 and 7 m/s impact velocities, the damage core crushing (C) is observed. [ABSTRACT FROM AUTHOR]

Plain fabric structure was analyzed and a predictive model of electromagnetic wave transmission was firstly constructed based on the weighted average method and equations of yarn curved surface, which can be used to predict the wave-transparency of plain fabrics. This model explains that the pitch, porosity, yarn cross-section and thickness of plain fabrics have a mathematical relationship with electromagnetic wave transmission. Five different parameters of S-2 glass fiber plain fabrics were tested in the range of 1∼18 GHz. Wave transmissions were positively correlated with the pitch, porosity and yarn cross-section. Wave transmissions were negatively correlated with thickness. The transmission trends of simulation and measurement were consistent with theoretical results, which proved the correctness of the proposed model. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polypropylene (GF-PP) composites have proven a great potential in the designation and manufacturing of control arms, leaf springs, barriers, beams and bridge decks. Two-pass injection molding of GF-PP was investigated in this study. Polypropylene (PP) was injected with different weight fractions (w%) of chopped glass fibers (GFs) with different fiber feedstock lengths (FFSLs). The composites were then crushed and re-injected once again. Some specimens were burned out to check the actual weight fractions and fiber lengths after the injection processes. The fiber lengths dramatically decreased due to damages during two-pass injection processes and crushing. The manufactured specimens were tested in tension, and the results indicated that the tensile strength increased slightly at w = 10% of GF. Further increase of GF weight fraction leads to a drop in the tensile strength below neat PP. The results of SEM micrographs showed an increase in air voids concentrations at high GF percentages which clarifies the reason behind the drop in the tensile strength. Also, in-plane shear tests were carried out using the Iosipescu fixture where a slight increase in the in-plane shear strength was noticed by increasing fiber weight fractions. In-plane shear moduli of all specimens were measured experimentally by strain gauges and calculated theoretically. The shear modulus was enhanced by glass fiber addition and a further increase was noticed by increasing the fiber weight fractions. [ABSTRACT FROM AUTHOR]

Single lap shear specimens were manufactured using resistance welding of carbon fibre reinforced substrates by means of CNT web-based heating elements. Heating elements were manufactured by embedding the CNT web layers between layers of PEKK/glass fibre and connecting them to copper electrodes. An experimental campaign explored their electrothermal behaviour influencing the welding process. Single lap shear specimens were then welded at a pressure of 0.05 MPa and different levels of power and duration. An optimum bond was obtained with a specific power of 80–90 kW/m2 and a time of 150 s, achieving a shear strength of 30 MPa. Post-mortem analysis revealed that fracture propagated within the substrates. This work represents a further step in the integration of CNT web-based heating elements in an industrial welding process. [ABSTRACT FROM AUTHOR]