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Highlights In this paper, the mechanical properties, damage modes, and bolt load distribution of the bonded‐bolted hybrid three‐bolt joint were investigated by a combination of experiments and numerical simulations. Acoustic emission (AE) was used to monitor the tensile process of the connection in real time, and the K‐means clustering algorithm was used to realize the cluster analysis of the damage modes. A numerical simulation model of the tensile process of the joint was established using ABAQUS simulation software. The progressive damage evolution of composite laminates, and adhesive layer was characterized by using the VUMAT subroutine, the B‐K failure criterion, and cohesive element with zero thickness, respectively. The results show that four main damage modes occur in composite laminates during tension: matrix cracking, delamination, fiber pull‐out, and fiber breakage, with corresponding peak frequency ranges of (0–80 kHz), (80–210 kHz), (210–330 kHz), and (330–375 kHz), respectively. The adhesive layer between the laminates mainly exhibits peeling failure because of the secondary bending effect. In the load‐bearing process, the adhesive layer was loaded first and failed, and the bolt loading was delayed. Meanwhile, the results of bolt load distribution showed that the bolts and the adhesive layer at both ends carried greater loads. Damage modes and damage evolution of the bonded‐bolted hybrid joint in tension were analyzed by combining acoustic emission technology and numerical simulation. The simulation of delamination damage in composite laminates was carried out by inserting zero‐thickness cohesive elements into the laminates, and the delamination damage between the carbon fiber layup and the adjacent glass fiber layup was analyzed. The effect of the inclusion of the adhesive layer on the mechanical properties of the joint and the distribution of the bolt load was analyzed. [ABSTRACT FROM AUTHOR]

To address the challenge of balancing load-bearing and electromagnetic (EM) wave absorption properties in aircraft composite skin, the outstanding mechanical and electrical characteristics of carbon fiber (CF) prepregs were utilized to construct a carbon fiber dual-polarized absorbing laminated structure (CFDALS). The bidirectional CF arrays were introduced into the glass fiber (GF) laminated structure, to endow the laminated structure with dual-polarized EM wave absorption performances. Additionally, the excellent load-bearing capacity of the CF reflector was used to enhance the mechanical properties. Simulation results indicate that, the CFDALS achieves an average absorptivity over 90% within the 8~18 GHz frequency band at incident angles of 0°~45°, and within the 5~18 GHz band at incident angles of 0°~60° for TE and TM polarized EM waves, respectively. The 3-point bending simulation results show that, the CFDALS exhibits higher specific flexural strengths and stiffnesses along 2 directions of the CF arrays while achieving dual-polarized EM wave absorption. Incorporation of bidirectionally arranged CF prepregs into GF prepregs enhances the dual-polarized EM wave absorption performance and the bidirectional flexural performance of the CFDALS simultaneously. The work provides a novel solution for the EM wave absorbing and load-bearing integrated design for aircraft composite skin applications. [ABSTRACT FROM AUTHOR]

Owing to the importance of fibre architectures in the design of textile composite materials, understanding their effect on the failure mechanisms of these composites have taken more considerations. In this regards, non-crimp preform and 2/2 twill fabric have been manufactured from glass fibre by using pin-board and power loom machines respectively, and subsequently composites laminates from both preforms are manufactured via vacuum assisted resin infusion method. In addition, quasi-static tensile and compressive strength tests have been conducted for the composite laminates that have same volume fraction. Damage failure mechanisms that occurred in compressive strength in both composites have been examined by using scanning electronic machine (SEM). Findings show that the mechanical properties are primly determined by fibre architectures and the presence of fibre crimp can further weaken tensile and compressive strength values. It was noticed that the tensile strength of non-crimp composite was 610 MPa whereas that of twill fabrics composite laminates it was found to be 350 MPa and 440 MPa in warp and weft directions respectively. Moreover, in case of twill fabric composites, fibre crimp has a considerable effect on the mode and characteristics of damage in the compressive loading; this leads to fibre fracture and kinks that primarily happened in the intersection point of warp and weft yarns. Results also showed improved ductility, strain to failure and absorbing energy in the twill fabric composites compared to non-crimp composites under in-plane shear strength test. [ABSTRACT FROM AUTHOR]

In this study, the axial compressive stresses of hollow circular composite tubes were investigated. For this purpose, hollow circular composite tubes with various inner diameters (Ø12 and Ø13 millimeters), a height of 80 millimeters, and an outer diameter kept constant at Ø17 millimeters were fabricated using a fiber winding process. In the production of hollow circular tubes, epoxy was used as resin, and glass fiber, carbon fiber, and Kevlar fiber were used as reinforcement materials. Experimental investigations were carried out for three different reinforcement materials, two thin-wall thicknesses, and five orientation angles. Axial compression tests were performed to research the influences of reinforcement materials, thin-wall thickness, and orientation angles on the compressive stresses. The axial compressive strength of the samples was observed experimentally by applying the load in the vertical direction. The reinforcement material, orientation angle, and thin-walled thickness had an important influence on the axial compressive stress. The glass/epoxy reinforcement material was found to have the highest axial compressive strength at 204 Mpa. When the orientation angle increased from 45° to 88°, the axial compressive stress increased by 2.27 times in glass/epoxy, 2.36 times in carbon/epoxy, and 2.37 times in Kevlar/epoxy specimens, respectively. In addition, by increasing the specimen wall thickness by 0.5 millimeters, the axial compressive stress at an 88° orientation angle increased by 9.67 % glass/epoxy, 11.85 % carbon/epoxy, and 7.14 % Kevlar/epoxy specimens. [ABSTRACT FROM AUTHOR]

The present experimental study assesses the mechanical properties of glass/carbon/glass hybrid composite laminates after being exposed to moisture in a deep freezer and elevated temperatures for extended periods. The top and bottom layers of the hybrid laminates are reinforced with glass fibre, and the middle layer is reinforced with carbon fibre using the epoxy matrix as a binder polymer material. The hybrid laminates were manufactured using the resin transfer moulding method, and their compressive and tensile properties were determined using a tensile testing machine. The storage modulus, loss modulus, and damping factors of all groups of laminates were identified using a dynamic mechanical analysis as a function of temperature and vibration frequency. The experimental results on compressive and tensile properties revealed slight variations when the hybrid laminates were kept at low temperatures in a deep freezer for extended periods. This might occur due to the increasing molecular crosslinking of the polymer network. As the testing temperature increased, compressive, tensile, storage modules, loss modulus, and damping factors decreased. This might occur due to the increasing mobility of the binder material. Particularly, the highest stiffness parameters were obtained at −80 °C/GCG (glass/carbon/glass) laminates due to the presence of a beta transition in the glassy region. The relationships between the glass transitions and the targeted frequencies were characterized. The values of the glass transition shift towards higher temperatures as the frequency increases. This might occur due to a reduction in the gaps between the crosslinking of the epoxy network when the frequency increases. The accuracy of the storage modulus results was compared with the empirical models. The model based on the Arrhenius law provided the closest correlation. Meanwhile, another model was observed that was not accurate enough to predict when gamma and beta relaxations occur in a glassy state. [ABSTRACT FROM AUTHOR]

The metallic bone fracture fixation plates are progressively being replaced by epoxy-reinforced glass fiber laminates (ERGFL) due to a higher strength-to-weight ratio and near neat shape manufacturing. Bone fracture fixation laminates are required to sustain the cyclic load due to the physical movement of the body. Therefore, the characterizations of glass fiber/epoxy laminates with drilled holes are important to study. Despite extensive research on the mechanical characterization of composite laminates, several unique circumstances remain unexplored, such as the characterization of glass fiber/epoxy laminates with drilled holes. The drilling laminates weakened the laminates' mechanical strength and damaged the area around the drilled hole. With Jo drill point designs, the greatest thrust forces (0.56 kN) were observed at 2800 rpm of cutting speed and 0.19 mm/rev of feed rate. Among the various drill points used, the drilled ERGFL laminates with Jo drill had the maximum fatigue life cycle of 87×10³. [ABSTRACT FROM AUTHOR]

The advantages of carbon nanotubes (CNTs) in fortifying the glass fiber reinforced polymeric (GFRP) composites are discussed in this paper. Bolted steel straps are utilized at the edges of composite plate to establish clamped conditions in the test setup. To minimize uncertainties caused by bolt attachments, a genetic algorithm-based model updating approach has been implemented by introducing artificial linear springs at the margins to achieve a better balance between theory and reality. The accuracy of the plate's results (natural frequencies and mode shapes) is verified, and the mechanical properties of randomly dispersed CNTs are incorporated in the formulations of folded plates. Remarkably, the motion equations are brought forward by the first order shear deformation theory (FSDT). Thereafter, two-directional generalized differential quadrature (2D-GDQ) technique is employed to determine natural frequencies from available motion, continuity, and boundary equations. The results of the folded plate are validated first by an experimental modal testing and finally some effective parameters such as folding angle, CNT weight ratio, boundary condition and flange-shape length are examined. [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 laminate was manufactured with T800 grade high toughness carbon cloth and carbon ribbon prepreg, T800 grade glass fiber prepreg, aramidon and quartz hybrid prepreg. The influence of high temperature and high pressure multiple curing on the mechanical properties of laminates was investigated. After five times of high temperature and high pressure curing, the laminate pore defects, bending strength and shear strength were tested. The results show that the internal quality of four different prepreg laminates is qualified. With the increase of curing times, the bending strength of T800 grade high toughness carbon cloth laminate decreases most obviously, and the shear strength of T800 grade glass fiber prepreg laminate decreases most obviously. However, the bending strength and shear strength of the four kinds of prepreg laminates decrease by less than 10%. The minimum shear strength of aramid and quartz hybrid prepreg after curing for five times is 1.64% lower than the theoretical index, and the shear strength of other materials is higher than the property requirements of each laminate. [ABSTRACT FROM AUTHOR]

As a consequence of their magnificent performance like mechanical, electrical and chemical properties, multiwalled carbon nanotubes (MWCNTs) are widely used as a secondary reinforcement in composite field. It has been developed by arc discharging process under atmospheric pressure. Subsequently, MWCNTs doped nano‐composite were developed through hand lay‐up and followed by vacuum bagging techniques. Quasi – isotropic symmetrical laminate of eight layers (0/90)/(±45)/(±45)/(0/90)//(0/90)/(±45)/(±45)/(0/90) were fabricated under room temperature. To fabricate the composite laminates, purified MWCNTs were homogeneously dispersed in glass fiber reinforced epoxy with 0.5%, 1.25%, and 2 wt% loading. Tensile strength, tensile modulus, strain to failure and fracture behavior of unfilled and MWCNTs doped composite laminates were evaluated. Field emission scanning electron microscope (FE‐SEM) was employed to evaluate the structural and morphological characteristics of advanced nano‐composites. Reinforcement effect is found to be more pronounced in 1.25% MWCNTs embedded glass fiber reinforced polymer. This reinforcement effect was corroborated by tensile fractography which depicted by hackle region. Results indicated that tensile strength of 1.25 wt% nano‐composite increased by 47.36% with respect to 0.5 wt% MWCNT doped composites. Highlights: Development of multi‐walled carbon nanotubes (MWCNTs) by arcing process.Fabrication of MWCNTs doped glass fiber reinforced polymer (GFRP) composites.Mechanical characterization of nano‐composites.Modeling of nano‐composites by Halpin‐Tsai equation.Fractrography of nano‐composites in details. [ABSTRACT FROM AUTHOR]

The use of hybrid reinforcement in polymer composites has been getting attention due to its potential for weight and cost reduction while achieving improved design flexibility for mechanical and thermal properties. In this study, an interply hybridization of epoxy laminates was performed using layers of solid and hollow glass fibers. The structural and thermal performance of the resulting hybrid vascular composites was investigated. All composite parts were manufactured using vacuum‐assisted resin transfer molding (VARTM), following an interply hybridization plan for the stacking sequence of hollow and solid fiber layers. An expected decrease in flexural properties and thermal conductivity was observed for the laminates with completely hollow fibers. On the other hand, hybridization had a positive effect on the laminate properties. It was shown that hybrid vascular composites could be manufactured without a significant reduction in mechanical and thermal performance by a judicious hybridization plan. The optimum hybridization of the laminate achieved a 3.1% increase in the specific flexural strength and a 5.3% decrease in thermal conductivity while containing a vascular network that can be used for active thermal control. Highlights: A vascular interply composite structure consisting of hollow and solid fibers was manufactured and characterized for the first time.The I4 composite, vascularized through the middle layers of the laminate, has almost as much flexural strength as solid composite and much more specific flexural strength.The thermal conductivity of the I4 composite is almost as much as that of the solid composite.Functional composites for thermal management and smart applications can be manufactured using hollow fibers without sacrificing flexural strength and thermal conductivity with interply vascularization. [ABSTRACT FROM AUTHOR]

This research investigates the influence of kevlar and glass fiber reinforcements on the mechanical and thermal properties of epoxy/vinyl ester (hybrid resin) composite. The hybrid resin was synthesized by achieving an interpenetrating network between epoxy and vinyl ester. The composites were characterized using tensile, flexural, impact, and thermo‐gravimetric analysis (TGA). Scanning electron microscopy was employed to analyze surface morphology whereas Fourier‐Transformation Infrared Spectroscopy (FT‐IR) was used to investigate the possible interaction between the constituents of the composites. The findings have shown a notable improvement in the mechanical properties after the hybridization of the resin. For reference, the tensile strength of glass/hybrid resin and kevlar/hybrid resin composites were observed to increase by 8.33% and 23.65%, as compared to glass/epoxy and kevlar epoxy composites respectively, whereas, the bending strength of these composites was improved by 8.36% and 30.61%, respectively. TGA also showed an enhanced thermal stability of the hybrid resin‐based composites. Such improvements are noticed due to multi‐resin incorporation (the oxirane group of epoxy reacts with the hydroxyl group of vinyl ester), confirmed by the FTIR, TGA, and morphological analysis. This study signifies that the proposed hybrid composites are better in terms of strength and modulus relative to conventional metallic materials. Highlights: The paper presents the development of novel hybrid resin, reinforced with synthetic fibers.Hybrid resin is imparted positively and is highly favorable in improving the mechanical properties of composites.The tensile strength of novel composites is increased by 8.33% and 23.65% relative to their base specimens, and a similar trend is observed in flexural and impact analysis.Fractured analysis showed that composite laminates deteriorated more intensely due to cohesive matrix fracture; adhesion failure was not observed at all, as evidenced by the emergence of micro‐cracks in resin.Developed novel composites exhibited maximum thermal stability; residual char in glass/epoxy/vinyl‐ester composite attained 17.81% higher, whereas kevlar/epoxy/vinyl‐ester achieved 3.56% relative to glass/epoxy and kevlar/epoxy base samples. [ABSTRACT FROM AUTHOR]

AbstractFibre reinforced metal laminates (FMLs) are widely used in various fields due to their excellent properties. However, the weak interlayer properties of FMLs limit their applications. In this paper, the interlayer properties of FMLs are enhanced by anodising the 2024-T3 aluminium alloy layer in FMLs or by epoxy matrix modification of graphene nanoplatelets (GNPs). The effect of both synergistic impacts on the interlayer properties of most FMLs is investigated. The FMLs were manufactured using the wet lay-up technique using 2024-T3 aluminium alloy, E51 epoxy and EW100 glass fibre. The results showed that the type I fracture toughness, tensile strength, flexural strength, interlayer shear strength and single layer shear strength of FMLs after anodic oxidation treatment were increased by 406.4%, 10.3%, 18.3%, 42.6% and 28.3%, respectively, compared with those of pure FMLs. The type I fracture toughness, tensile strength, flexural strength, interlayer shear strength and single layer shear strength of the GNPs-modified FMLs matrix were increased by 280.4%, 3.7%, 6.8%, 34.5% and 19.1%, respectively, compared with those of pure FMLs. Moreover, the synergistic effect of FMLs indicates that the simultaneous anodic oxidation and GNPs modification of FMLs can lead to the best mechanical properties of FMLs. Microscopic images and schematics illustrate the toughening mechanism of anodising and GNPs, including the enhancement of aluminium/resin interface and fibre/resin interface and the enhancement of resin matrix properties. [ABSTRACT FROM AUTHOR]

In defense and military applications, the growing use of radar technology necessitated the development of effective stealth solutions for military equipment like drones and fighter jets. This paper explored a new approach that glass fiber mat coated with various concentrations of grapheme embedded polyvinylidene fluoride (PVDF) nanofibers using electrospinning technique and stacked the Graphene/PVDF/Glass fiber mat layers by epoxy resin and hardener to form the glass fiber laminate composite by hand layup technique to enhance the electromagnetic wave absorption. These research findings demonstrated that composite materials were more successful than metals at absorbing electromagnetic waves. The tailored composite showed above 80% increase in electromagnetic absorption over conventional metal in the X-band (8–12 GHz), although having a minimum thickness of 3 mm. According to X-ray diffraction, PVDF/Graphene nanofibers had improved electroactive β-phase behavior when compared to pure PVDF nanofibers. The PVDF/graphene nanofibers which have an average diameter of 80–160 nm, were seen using scanning electron microscopy. The tailored composites also had simple configuration and mechanical characteristics that were improved when compared to plain glass fiber laminate composite. In comparison to all other configurations, experimental findings showed that the composite with 0.5 wt% Gp/PVDF had a wide band absorption of above 90% in all the frequencies. This innovative method of fabrication of the tailored Gp/PVDF nanofibers coated glass fiber laminate composite provided a promising strategy in the manufacture of military equipment and stealth fighters. [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]

Vinyl esters are increasingly being used as the matrix polymer in fibre-reinforced composites for demanding large applications which experience long-term exposure to moist and wet conditions. This paper presents the results of a study of ageing due to moisture absorption in vinyl ester polymer and glass fibre–vinyl ester laminates. The moisture uptake kinetics of the two neat VE polymers, cured at different conditions, and their glass-reinforced composites has been characterised by gravimetric methods. These studies have been carried out using submersion in water at 23 °C and 50 °C and exposure to high relative humidity moisture conditions at room temperature. A dynamic mechanical analysis characterisation of the glass transition temperatures of both the aged matrix and the composite is also presented. [ABSTRACT FROM AUTHOR]

Elium® Acrylic/Glass Fiber thermoplastic laminate composites are liable to develop irreversible local defects under quasi‐static loading. To reinforce the damaged material, repair is a cost‐effective mechanical alternative. The present study investigates the tensile behavior of an Elium® glass‐fiber‐based acrylic laminate composite panel, repaired by vacuum bonding with Elium® repair resin and double overlap of external patches (DP). The results obtained for all repaired laminate composites E190/GF_D(10, 20, 30)R with diameters 10, 20, and 30 mm showed an improvement in the mechanical properties of the repaired panels, compared with the drilled and pristine samples. Average load recovery rates were significant for E190/GF_D10R (7.9%, 3.55%, 13%) E190/GF_D20R (23%, 18%, 3.32%), E190/GF_D30R (7.2%, 9.36%, 32.37%) at strain rates of 0.001, 0.01, and 0.05 s−1 respectively. Finite element (FE) models for the virgin, drilled, and repaired composite, performed by coupling the Hashin criteria with the cohesive zone model (CZM), provided a relevant prediction of intra‐ and interlaminar failures of these woven laminated composites. Highlights: The effect of vacuum bonding repair with Elium E351 EOT resin was studied.Symmetrical repair of acrylic laminate drilled by fiberglass patches.Tensile strength of the repaired laminates was investigated.Intra‐ and interlaminar damage was predicted by finite elements modeling. [ABSTRACT FROM AUTHOR]

The present study investigates the flexural failure properties of a hybrid laminate beam subjected to three-point bending. A symmetrically laminated hybrid beam is constructed using high-strain and inexpensive glass fibre on the top layers and low-strain and expensive carbon fiber on the middle layers. Classical lamination plate theory is used to find the stress and strain distribution that occurs due to the bending moment on the compressive side. The theoretical failure limits of the laminated hybrid beam are analyzed considering the targeted span-to-depth ratios, volume fractions of the fibers and hybrid ratios using the Tsai-Wu failure criterion and Matlab codes. Using the graph of failure index versus hybrid ratios, the minimum thickness of carbon fiber needed for the delay of failure and cost efficiency of the laminated hybrid beam is identified by applying the linear interpolation method. The numerical results indicate that the failure index increases with the increasing loading span and decreases when the volume fraction of fiber increases. In particular, the placement of glass fiber on the top layer of the laminated hybrid beam might have contributed to obtaining higher strains and curvatures before the catastrophic failure properties of carbon fiber. The flexural stiffness of the laminates is found to increase when the hybrid ratio increases. Overall, it is noted that the theoretical analysis is one method that is less time-consuming and cost-effective than other alternative approaches, such as finite element methods and experimental tests to estimate the minimum thickness of high-stiffness and the expensive material needed to maintain the strength and stiffness of the hybrid composite structures over long periods. [ABSTRACT FROM AUTHOR]

This study looks at the mechanical and free vibration properties of glass laminated with functionalized aluminium reinforced epoxy. NaOH, K2Cr2O7, Fe2(SO4)3. XH2O, and C8H18O3Si were employed to functionalize aluminum. The flexural, impact, and shear strengths, as well as their failures, were investigated using electron microscope images. The impulsive hammer approach was applied to investigate laminate vibration behaviour. The results showed that the flexural strength (623.83 MPa), impact strength (76.41 J/mm2), and shear strength (55.31 MPa) of C8H18O3Si functionalized laminates outperformed those of other functionalized laminates. The improvement of mechanical properties was due to the change in interfacial adhesion. This is dependent on the functionalization of aluminium used in stacked laminates. Moreover, C8H18O3Si functionalized laminates exhibit a higher natural frequency and higher damping than other functionalized laminates. This natural frequency and damping are enhanced due to the strong mechanical interlocking between polymer and metal adhesion. It was noted that the same laminates have higher toughness than other laminates because of the high impact energy obtained. [ABSTRACT FROM AUTHOR]

An evaluation of the interlaminar fracture toughness of polyamide/glass fiber laminates with various layups is reported. Due to large differences in thermal expansion coefficients of fiber and binder the laminates with layups where single layers are swapped exhibit high warping. A technique for avoiding this is proposed, allowing evaluating interlaminar fracture toughness of various angle interfaces. Two different layups for evaluating the Mode I and II interlaminar fracture toughness are tested. The differences of delamination behavior of a number of different-angle fiber interfaces are shown and analyzed. The applicability of the proposed testing technique is discussed. [ABSTRACT FROM AUTHOR]

"Interleaving" is widely used for interlaminar toughening of fiber-reinforced composites, and the structure of interleaving is one of the important factors affecting the toughening efficiency of laminates. Several experiments have demonstrated that compared to continuous and dense structures, toughening layers with structural heterogeneity can trigger multiple toughening mechanisms and have better toughening effects. On this basis, this work further investigates the application of heterogeneous toughening phases in interlaminar toughening of bidirectional GFRP. CNT was selected to construct toughening phases, which was introduced into the interlaminar of composites through efficient spraying methods. By controlling the amount of CNT, various structures of CNT toughening layers were obtained. The fracture toughness of modified laminates was tested, and their toughening mechanism was analyzed based on fracture surface observation. The results indicate that the optimal CNT usage (0.5 gsm) can increase the initial and extended values of interlayer fracture toughness by 136.0% and 82.0%, respectively. The solvent acetone sprayed with CNT can dissolve and re-precipitate a portion of the sizing agent on the surface of the fibers, which improves the bonding of the fibers to the resin. More importantly, larger discrete particles are formed between the layers, guiding the cracks to deflect in the orientation of the toughened layer. This generates additional energy dissipation and ultimately presents an optimal toughening effect. [ABSTRACT FROM AUTHOR]

Nowadays, fiber stacks are extensively used in the aircraft and structural component manufacturing industries. It is mainly due to their excellent mechanical and physiochemical performances. The different stacking sequences of fiber materials expand the structural properties due to high-strength carbon fiber and low-cost glass fiber. The fragile and anisotropic conduct of Carbon (Cf) and Glass (Gf) laminates generates different types of complex machining issues. This article focuses on the Drilling test of Carbon/glass fiber hybrid composites using different stacking sequences. The effect of varying stacking orders is explored in this study to identify a feasible composite. The control of varying constraints, namely, spindle speed (N), feed rate (f), and stacking sequence (SS) of carbon (Cf) and glass fiber (Gf) reinforcement, is performed to achieve the optimal parametric condition. The finding reveals that sample A (C4G4) stacking sequence provides an acceptable value for thrust force 59.05 N and delamination 1.0001 for high drilling efficiency. The stacking technique of carbon/glass layers can be endorsed to the manufacturing sector for cost-effective composite development and a defect-free machining environment. [ABSTRACT FROM AUTHOR]

This paper deals with an innovative nondestructive technique for composites (local-IET), which is based on the Impulse Excitation Technique (IET) and, in the presence of damage, assesses the degradation of the elastic properties of a local region of the laminate by reversibly clamping its boundaries. In this paper, a numerical analysis of the sensitivity of the local-IET to the delamination damage mechanism is conducted. Firstly, a Finite Element (FE) model of the local-IET test is determined through experimental investigations on undamaged composite laminates, which cover a wide range and are made of glass or carbon fibers, through resin infusion or pre-preg consolidation and with unidirectional or fabric textures. The vibrational response of a glass fiber composite with local delamination is then assessed with the local-IET. By modeling the delamination in the simulation environment, the effectiveness of the FE model in replicating the vibrational response, even in the presence of delamination, is shown through a comparison with the experimental results. Finally, the FE model is exploited to perform a sensitivity analysis, showing that the technique is able to detect the presence of delamination. [ABSTRACT FROM AUTHOR]

The mechanical performance of timber composite floors is influenced by the degree of composite action between the components. In this study, the shear strength performance of cross-laminated timber and glued laminated timber composite floors based on the joining method was evaluated by push-out test. Eight types of timber-timber composite joints were evaluated using three different methods: lag screw joints, glued-in rod joints using fully threaded bolts and glass fiber reinforced plastic, and hybrid joints. Strength characteristics were derived to make theoretical predictions on the load-carrying capacity of the joints. The results showed that the glued-in rod joints were superior to the lag screw joints, with slip coefficients and ductility measured as 10 times and 2.5 times higher, respectively. The reliability of the strength characteristics of the glued-in rod joints was remarkably different depending on the presence or absence of anti-adhesive tape applied to the timber-to-timber joint surface. The load capacity of the hybrid joint, which combines mechanical and glued-in rod joining methods, was 47% higher than that of the lag screw joint and 38% higher than that of the glued-in bolt joint. In the European Yield Model modified to estimate the load capacity of joints, the rope effect and the yield moment of the fasteners had a remarkable impact on the predicted load capacity. [ABSTRACT FROM AUTHOR]

Degradation of polymer composites is a significant problem in many engineering aspects. Due to the interaction of various degradation factors during the exploitation of composites, a synergistic effect of destruction is observed. The article describes the phenomena occurring in glass fiber reinforced polyester laminates under the influence of ultraviolet radiation (UV) in an aquatic environment. The laminates were exposed to UV-A, UV-B and UV-C radiation for 1000 h in free-air and underwater conditions. During the test, the materials were immersed at stable depth of 1 mm and 10 mm, respectively. The three-point bending tests performed on the samples after being exposed to UV showed an increase in the flexural strength of the composites. Simultaneously, degradation of the outer surface layer was observed. The degradation removed the thin resin film from the surface which resulted in a direct exposure of the reinforcing fibers to the environment. The transformations taking place in the deeper layers of the composite increased the mechanical strength due to the additional cross-linking reactions excited by the energy arising from the radiation. Moreover, the formation of polymer structures from free styrene remaining after the technological process and the occurrence of free radical reactions as a result of the cage effect was also observed. [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]

Composite materials are increasingly used in aircraft structural components with complex structures like L, C, or T shapes, which can cause delamination failure in the thickness direction under complex loading. This research focuses on the experimental investigation of the effect of different adhesive reinforcement phases with an adhesively bonded external patch to examine the residual strength and delamination resistance of repaired glass/epoxy curved samples. The damaged region in curved samples was repaired using adhesive reinforcement phases like neat epoxy, chopped glass fiber, and particulate glass fiber, along with adhesively bonded external patches like hybrid patches of glass/Kevlar (HP G/K), glass/carbon (HP G/C), and intraply patch carbon/Kevlar (IP C/K). The findings show that chopped glass fiber HP G/C patch-repaired curved samples had a curved beam strength (CBS) and interlaminar tensile strength (ILTS) recovery of 222.87% and 149.54%, respectively, as compared to damage area removed samples. In addition, it exhibited higher peak force, residual strength, and less elongation when compared to HP G/K and IP C/K patch-repaired curved samples. According to the findings of this research, composite angle brackets in aircraft structural components can be repaired utilizing an adhesively bonded HP G/C patch filled with chopped glass fiber at the dressed site. Highlights • The effect of patch hybridization on repaired curved laminates was studied. • Four-point bending test was conducted on indented and repaired samples. • Residual strength and delamination behavior were studied. • Chopped glass fiber HP G/C patch repaired samples had higher CBS and ILTS. • Delamination onset and propagation were assessed using Photographic images. [ABSTRACT FROM AUTHOR]

In the present work, four layered Palmyra-Palm-Leaf-Stalk (PPLSF)/Glass hybrid composites laminates with six distinct stacking orders were made by following hand lay-up method. Different experiments were carried out to determine the tensile, flexural, impact and hardness of the laminates as per ASTM standard. The results reveal that the addition of glass fiber to PPLSF significantly enhanced the mechanical performance of the laminates. On successive replacement of PPLSF by glass fiber, an enhancement of properties such as 291.39% for tensile strength, 72.08% for flexural strength, 75.82% for impact strength, and 78.44% for micro-hardness was observed. Again, it is also noticed that the stacking order plays an important role in influencing the properties while comparing experimental finding of laminates with equal weight percentages PPLSF and glass fiber. Further to perform Finite Element Analysis (FEA), a 3D CAD model of tensile and flexural specimen was created in space-claim modeler of ANSYS R19.0 and subsequently imported to generate numerical predicted values. While comparing the numerical and experimental results, there was very good agreement among the results was found. Scanning Electron Microscope (SEM) was used for fractography analysis of the tested samples to examine the different mode of failures. [ABSTRACT FROM AUTHOR]

To detect the debonding defect of glass fiber reinforced polymer (GFRP) laminate, the lock-in infrared thermography non-destructive testing system is built and the systematic testing research are conducted, and the effect of different geometrical parameters of debonding defects on the testing results are analyzed. Algorithms such as inter frame differential-multi frame cumulative average method, polynomial fitting-correlation coefficient method, and time-difference contrast method are used to process the image sequence, and signal-to-noise ratio and information entropy are defined as the parameters for evaluating the performance of algorithms. [ABSTRACT FROM AUTHOR]

Lightweight component design is effectively achievable through sandwich structures; many past research studies in the aerospace and racing sectors (since the 1920s) have proven it. To extend their application into the automotive and other transport industries, manufacturing cycle times must be reduced. This can be achieved by sandwich materials made of continuous fibre-reinforced thermoplastic (CFRTP) cover layers and thermoplastic honeycomb cores. To widen the application of flat thermoplastic-based sandwich panels into complex parts, a novel forming technology was developed by the Fraunhofer Institute of Microstructure of Materials and Systems (IMWS). Manufacturing defects like wrinkling and surface waviness should be minimised to achieve high reproducibility of the sandwich components. Studying different manufacturing parameters and their influence on the final part is complex and challenging to analyse through experiments, as it is time-consuming. Therefore, a finite element (FE) modelling approach is implemented to reduce such efforts. Initially, a thermoforming model is developed and validated with experimental results to check its reliability. Further, different simulations are performed to optimise the novel sandwich-forming process. In this study, a thermoplastic sandwich made of polypropylene (PP) honeycomb core and polypropylene glass fibre (PP/GF) cross-ply as cover layers was used, and its numerical model was executed in LS-DYNA software release R11.2.1. [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]

In this paper, the repeated low velocity impact responses and compression‐after‐impact (CAI) behaviors of woven glass fiber‐reinforced composite laminates were studied at the same total impact energy. Three types of impact energies, 30, 40, and 60 J, were chosen for the repeated impact tests relative to the single 120 J impact event. The impact behaviors including impact contact force–displacement and energy–time curves during the impact testing were recorded. The variations of the impact mechanical characteristics such as peak impact force, maximum displacement, and energy absorption were evaluated. The methods of visual inspection and stereo microscope were applied to identify the damage morphology of the impacted laminates. The damage accumulation was evaluated employing the absorbed energy fraction and normalized maximum displacement. It was found that the influences of impact energy on the repeated impact mechanical response are more remarkable than that of the impact number, and the impact events with fewer impact numbers cause more damage to the laminates for the same accumulative impact energy. Furthermore, the load–displacement and the CAI strength versus impact number curves were compared for the CAI testing. The ultimate load and the resulted CAI strength decrease with the increase of impact number owing to the influence of damage accumulation in repeated impacts. Highlights: Repeated impact responses were studied at the same total impact energy.The impact energy makes significant influence on the impact dynamic responses.The impact events with fewer impact numbers cause more damage to the composites.The CAI behavior was explored considering the effect of damage accumulation.The CAI strength of damaged laminates decreases with impact number increasing. [ABSTRACT FROM AUTHOR]

The objective of this study is to produce bidirectional woven carbon/glass fiber reinforced epoxy hybrid composites and to assess their fracture toughness (FT) and low‐velocity impact strength. The composites were produced for the study by changing the stacking order of fiber layers using a vacuum assisted resin infusion process. In addition, the consequence of halloysite nano‐clay addition on the above properties were explored. The outcomes disclosed that the arrangement of fiber layer notably influences the FT and low‐velocity impact strength of the composites. Particularly, the addition of more carbon fiber layers played a key role in enhancing the FT of hybrid composites, while a reverse trend was observed for low‐velocity impact strength of composites due to the elastic nature of glass fibers, which absorbs more energy through global deformation. Additionally, the incorporation of halloysites enhanced the FT and impact strength of hybrid composites due to increased interfacial adhesion between composite elements. In addition, morphological analysis was conducted to evaluate the damage morphologies and failure mechanisms of tested laminates, which offers crucial information for the structural design of these laminates as well as for the enhancement of their performance. Highlights: Fracture toughness and impact strength of hybrid composites were investigated.Arranging carbon fibers on the extreme layers enhanced the fracture toughness.Glass fiber used in hybrid composite supports to increase their impact strength.Addition of halloysite improved the overall performance of hybrid composites. [ABSTRACT FROM AUTHOR]

To evaluate the severity of thermal degradation on the impact response of carbon (C) and glass (G) fibers reinforced PolyEther Ether Ketone (PEEK) laminates, low velocity impact tests were conducted at a temperature higher than the glass transition temperature Tg (150°C) and after exposure to a kerosene flame (5-10-15′). The first important effect resulting from temperature increase was a reduction of the impact energy required to induce BVID (Barely Visible Impact Damage). The second effect was that matrix ductility (enhanced at T>Tg) contributes to significantly modify the permanent indentation. Not surprisingly, the plastic and viscoplastic deformation mechanisms being ruled by the PEEK matrix behavior at high temperature, the permanent indentation increases by almost 40% for all impact energies. Contrary to the external damage represented by permanent indentation, temperature has a tremendous influence on the internal damage as there was virtually no delamination in the CG/PEEK laminates impacted at Room Temperature (RT) and 150°C. At last, impact tests conducted on specimens exposed to a kerosene flame implied that the impact bearing capabilities of CG/PEEK laminates dramatically decreased after a 5′ exposure and became even critical after 10′ as perforation was observed. For 40 J impacts, the permanent indentation was multiplied by 3–9 with respect to the as-received specimens. [ABSTRACT FROM AUTHOR]

Due to the high interest in the use of glass/epoxy laminates in aerospace applications, aviation, and as cryogenic tanks, it is crucial to understand the behavior of composites under challenging environmental conditions. Polymer composites are exposed to low temperatures, including cryogenic temperatures, which can lead to the initiation of microdamage. This paper investigates damage initiation/accumulation and its influence on the properties of cross-ply woven glass fiber epoxy composites at low temperatures compared to room temperature conditions. To evaluate the influence of a low-temperature environment on the mechanical performance of glass fiber reinforced epoxy composite (GFRP) laminates, three types of test campaigns were carried out: quasi-static tensile tests and stepwise increasing loading/unloading cyclic tensile tests at room temperature and in a low-temperature environment (−50 °C). We demonstrated that the initial stiffness of the laminates increased at low temperatures. On the other hand, there were no observed changes in the type or mechanism of developed damage in the two test conditions. However, the reduction in stiffness due to the accumulated damage was more significant for the laminates tested at low temperatures (~17% vs. ~11%). Exceptions were noted in a few formulations where the extent of damage at low temperatures was insignificant (<1%) compared to that at room temperature. Since some of the studied laminates exhibited a relatively minor decrease in stiffness (~2–3%), we can also conclude that the formulation of matrix material plays an important role in delaying the initiation and formation of damage. [ABSTRACT FROM AUTHOR]

The screw pine and E-glass fibers were hybridized in the vinyl ester resin matrix to prepare the hybrid composite laminates in the present communication. Hybrid composite laminates at the constant volume fraction of 35.12% has been fabricated using the hot press compression molding in two forms, namely dispersed and skin-core, to evaluate the mechanical properties. Mechanical properties of composite laminates were studied based on the various volume fraction of glass fiber content (0, 3.32, 8.15, 12.44 and 16.53 vol.%). The scanning electron microscopy (HITACHI S-3000N) was used to study the fracture surface of composite laminates. The results of hybrid composite laminates were compared with a neat resin sample and screw pine fiber (35.12 vol.%) alone composite. The results revealed that the mechanical properties of both the type of composite laminates increased as glass fiber addition was increased. The SPF18.59/GF16.53 hybrid composite laminate exhibits the highest level of mechanical properties because of the concentration and higher elongation percentage of glass fibers. Moreover, the skin-core type composites perform better than those of the dispersed type hybrid composites. Because of the stretching nature of screw pine fibers, they elongate when the load is transferred from glass fibers to screw pine fibers, resulting in an increase in mechanical properties. The property values were predicted using a theoretical model, and it was found that the two were in good agreement. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to investigate usability of resistance welding joining method for poly (aryletherketone) (PAEK) thermoplastic matrix/carbon fiber (CF) reinforced composite laminates (PAEK/CF). For this purpose, effects of six different Interlayer Forms having different stainless steel meshes as Heating Elements and different woven glass fiber forms as Insulating Layers were studied. After determining welding parameters for each specimen group, performance of the resistance welding operations was compared by ultrasonic inspection, microscopic examination, DSC analyses, and by three different interlaminar mechanical tests. Analyses and tests generally revealed that use of stainless steel meshes as Heating Elements could supply proper amperage level for the heating, melting and crystallization stages of the PAEK matrix during welding consolidation. Depending on the lay-up configuration of Interlayer Forms, "amperage levels" determined for the heating, melting dwell and crystallization dwell were in the ranges of 46–100 A, 40–90 A and 25–50 A, respectively, It was also observed that in order to prevent Current Leakage problem to the other layers in the composite laminate, rather thicker and heavier woven glass fiber forms as Insulating Layers should be used. Otherwise, not only voids could form in the thermoplastic matrix, but also delamination might occur in the upper or lower PAEK/CF composite laminates being welded. When thicker and heavier insulating layer was used; interlaminar mechanical properties of Single Lap Shear Strength, Fracture Toughness under Mode-I and Mode-II were determined as high as 36.77 MPa, 3.76 kJ/m2 and 4.71 kJ/m2, respectively. [ABSTRACT FROM AUTHOR]

Composite laminates have found extensive application in various industries, and numerous studies have been conducted to investigate their behavior in flat sheet configurations. The present study aims to extend this research by examining the behavior of convex composite specimens subjected to high velocity impact (HVI), and comparing their energy absorption and failure area to that of flat sheets made of glass fibers. Additionally, we seek to investigate the influence of curvature diameter on the energy absorption and fiber failure percentage of the composite specimens. Four series of composite laminates with distinct geometries, comprising a flat specimen and three convex composite specimens, were fabricated with nine layers each and diameters of 10, 15, and 20 cm. All specimens were fully clamped and subjected to empirical gas gun impact tests at three different velocities of 200, 250, and 300 m/s. The velocity values before and after the impact were measured using velocity sensors, and the energy absorption of the laminates was computed. Of the tested composite specimens, those with smaller diameters and greater curvature exhibited reduced fiber damage percentage and increased energy absorption. Compared to the flat specimens made of glass fibers, the convex specimens with a diameter of 10 cm exhibited an energy absorption increase of approximately 47%, while the specimens with diameters of 15 and 20 cm showed approximately energy absorption increases of 42% and 7%, respectively. The results were confirmed through simulation using finite element software ABAQUS/Explicit. Highlights: Curved E‐glass laminates studied under high velocity impact which is done experimentally and numerically.Convexity increases energy absorption capacity of E‐glass reinforced epoxy composites.The results show that convexity can absorb more energy compared to flat panels.The damaged area of curved laminates are smaller than the flat one.The findings suggest that convexity can be a useful design feature for improving impact resistance in various applications. [ABSTRACT FROM AUTHOR]

Orthotropic rectangular plates, featuring central cutouts and subjected to in-plane loading, are extensively employed across various engineering fields, including mechanical, automobile, aerospace, and marine. The introduction of a cutout inevitably leads to stress concentration within the plate. Incorporating carbon nanotubes (CNTs) into the polymer matrix composite has been noted to induce significant heterogeneity in stress fields. Functioning as bridges between the fibers and the matrix, CNTs can effectively mitigate stress concentration and enhance the damage tolerance of the composite. However, accurately determining stress concentration in CNT-based composites requires comprehensive understanding of the geometric discontinuity edge and well-defined evaluation techniques. Among these, the finite element method emerges as a straightforward yet precise approach for studying stress concentration around geometric discontinuities. The present work harnesses the finite element method to investigate stress concentration in CNT-based multiscale composite plates (Glass Fiber/CNT/Epoxy) with central cutouts under static in-plane loading. To validate the model, the derived results are compared with analytical data from conventional composite materials. Moreover, the impact of cutout size on stress concentration is examined for three distinct configurations: plates with a central circular cutout, plates with an elliptical central cutout (major axis in the longitudinal direction), and plates with an elliptical central cutout (major axis in the transverse direction). Preliminary findings suggest a correlation between increased cutout size and augmented percentage reduction in stress concentration. Notably, the maximum percentage reduction in stress concentration is observed in the case of plates hosting an elliptical cutout at the center with the major axis aligned in the transverse direction. [ABSTRACT FROM AUTHOR]

Now a day, there is a huge trend in research and development of bio-based products which have a wide variety of replacement for naturally existing materials. The current research intends to determine the qualities of a composite laminate material consisting of maize husk and glass fibre. The composite is created by alternately overlaying glass fibre cloths on corn husk fibre layers. The required composition and thickness are achieved by calculation of number of the layer of each fibres. The epoxy resin and hardener by weight is mixed in the ratio 10:1 respectively. It is poured between the layers of the composite to generate adhesion. Hand lay-up technique is adopted in manufacturing of the material and the material is pressed for certain duration using nut and bolt template assembly allowing it for natural curing. The composite is been tested for bending, tensile and water absorption tests according to standards. [ABSTRACT FROM AUTHOR]

Laminated composites with complex structures, such as L, C, or T-shaped geometries, are used at junction parts in the automotive and aerospace industries. Due to delamination failure in the curved or angled region, these structures are relatively weak in the through-thickness direction when subjected to complex loading. To overcome the issue of weak delamination resistance, this study is aimed at investigating the effect of various reinforcements on the strength properties and delamination resistance of glass/epoxy curved laminates under a four-point bending test. Experimental research was carried out on glass/epoxy curved laminates strengthened by combining three different types and geometries of reinforcement. These included chopped short fibers and glass fiber patches between each ply at the corner region of curvature, and stitching of aramid filament at the corner region of 90-degree bending. A 4 mm pitch interval was observed to enhance curved beam strength, interlaminar tensile strength and delamination resistance. The obtained findings show that glass/epoxy curved laminates reinforced with chopped kenaf short fiber, 45° glass fiber and a single stitch at the corner show greater enhancement in curved beam strength by 52.7, 34.3, and 5.6%, respectively, compared to the baseline sample. Similarly, interlaminar tensile strength improved by 69.3, 40, and 78.5% compared to the baseline sample. On the other hand, curved laminates needled with a single stitch at the corner show higher delamination resistance than other reinforcements. The experimental results correlate well with the damage morphology indicated in SEM fractographic images. [ABSTRACT FROM AUTHOR]

Currently, hybridization of natural-synthetic fibers within a polymeric matrix has received wide attention owing to its promising properties. This study investigated the mechanical properties of interply and intraply hybrid jute (J)-glass (G) fiber/epoxy composites. The mechanical properties (i.e., tensile, flexural, and impact) of the pure jute, pure glass, and their hybrid composites were evaluated. The prepared composite samples consisted of five plies of woven fabrics. Interply hybrid composites comprised three layering sequences: G3JG, GJGJG, and 2GJ2G. Intraply hybrid composites of similar co-woven plies were fabricated by either the alternative replacement of a single glass yarn with a single jute yarn (G1J1) or two jute yarns (G1J2). The results showed that increasing the glass fraction in the interply hybrid composites improved their tensile properties. The two intraply hybrid composites provided almost similar tensile moduli, while the tensile strength of the G1J1 samples was approximately 41% higher than that of the G1J2 counterparts. The maximum flexural properties were provided by 2GJ2G composites, followed by GJGJG, and they were interestingly higher than those of pure glass composites. The G1J1 intraply hybrid composites offered a higher flexural strength and a lower flexural modulus than those provided by the pure glass composites. Compared to the pure glass composites, the impact strengths of the 2GJ2G and GJGJG samples decreased by 4% and 16%, respectively. In summary, the GJGJG hybrid composites exhibited the highest specific tensile, flexural, and impact properties compared to the other hybrid composites. [ABSTRACT FROM AUTHOR]

Poor interlaminar fracture toughness has been a major issue in glass fiber-reinforced epoxy resin (GF/EP) laminate composites. In this paper, soft carboxy-terminated nitrile (CTBN) rubber particles and rigid nano-SiO2 are used to toughen the epoxy resin (EP) matrix to improve the interlayer properties of GF/EP laminate composites. The effects of adding two toughening agents on the mechanical and interlayer properties of GF/EP laminates were studied. The results showed that adding the two kinds of particles improved the mechanical properties of the epoxy matrix. When the additional amount of flexible CTBN rubber particles was 8 wt%, and the rigid nano-SiO2 was 0.5 wt%, the fracture toughness of the matrix resin was increased by 215.8%, and the tensile strength was only decreased by 2.3% compared with the pure epoxy resin. On this basis, the effects of two kinds of particles on the interlayer properties of GF/EP composites were studied. Compared with the unmodified GF/EP laminates, the interlayer shear strength and mode I interlayer fracture toughness is significantly improved by a toughening agent, and the energy release rate GIC of interlayer shear strength and interlayer fracture toughness is increased by 109.2%, and 86.8%, respectively. The flexible CTBN rubber particles and rigid nano-SiO2 improve the interfacial adhesion between GF and EP. The cavitation of the two particles and the plastic deformation of the matrix is the toughening mechanism of the interlayer properties of the composite. Such excellent interlaminar mechanical properties make it possible for GF/EP laminates to be widely used as engineering materials in various industries (e.g., aerospace, hydrogen energy, marine). [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]