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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]

In a multi-component system, the interfacial interactions between the various components trigger the behavior of the composite under external loading and thus determine the bulk properties of the material. In the present work, composite laminates made from TiO2 modified epoxy reinforced with glass fiber are subjected to thermal loading and the effort is made to analyze the interfacial interactions through the experimental values of storage modulus, loss modulus and tan delta. The loading of TiO2 nanoparticles in the epoxy resin is varied to also understand the effect of nanoparticle addition on the interfacial interactions through DMA. The addition of TiO2 nanoparticles helped to increase the storage and loss modulus by improving the rigidity of the polymeric chain. To understand the effect of varying the loading of TiO2 nanoparticles and to gauge the optimum wt.% addition of such nanoparticle, Tan delta, the degree of entanglement and the coefficient of the effectiveness of the nanofiller is found and the results indicate that the laminates successfully withstand the applied thermal load when the TiO2 loading is kept at 2 wt.%. This optimum nanoparticle loading wt.% is further validated through the adhesion factor which is found with the help of Tan delta values. [ABSTRACT FROM AUTHOR]

In the present work, the mechanical and morphological characterization of bamboo-glass fiber-nanoclay epoxy hybrid composites is carried out. Materials are prepared using a hand lay-up process with different wt.% of bamboo fiber, glass fiber, nanoclay, and epoxy. As per ASTM standards, fabricated composite laminates are cut and tested for tensile and flexural properties. The bamboo fiber epoxy composites (BFEC) display the tensile and flexural strength of 137 and 170 MPa, respectively. Hybrid composites, viz. bamboo-glass fibers epoxy composites (BGFEC), display improved tensile (180–240 MPa) and flexural (225 to 320 MPa) strengths compared to BFECs. Glass fiber epoxy composites (GFEC) display maximum tensile (265 MPa) and flexural (360 MPa) strengths among all the composites. Furthermore, the addition of nanoclay improves the tensile (by 6 to 8%) and flexural (by 8 to 10%) strengths of epoxy, BFEC, BGFEC, and GFECs. SEM analysis is conducted for fractured tensile specimens to understand the reasons for specimen failure. [ABSTRACT FROM AUTHOR]

For commercial civil applications of laminated composite material, characterizations to forecast the interlaminar shear behavior and viscoelastic response across a wide temperature range are essential. In this study, the interlaminar shear strength (ILSS) of glass/epoxy (GE) composites dispersed with binary nanofillers nanosilica‐multilayer graphene (NS‐MLG) and nanosilica‐nanoclay (NS‐NC) was analyzed at an in‐situ testing temperature of 20, 70, and 110°C. Further, the viscoelastic property of the composites was studied using a dynamic mechanical thermal analyzer (DMTA) in the temperature range of 35–165°C. An increase in the ILSS value of around 9% and 10% was observed at room temperature for GE/MLG‐NS and GE/NC‐NS, respectively, compared to control GE composites. In contrast, the trend was seen to change at higher temperatures. There was a slight decrement in the storage modulus (E′) of GE/MLG‐NS and GE/NC‐NS composites in the glassy region compared to control GE composites. The mean Tg of the GE composite (control) was nearly 107.3°C when the E′ decline onset temperature was taken into account, but after the addition of MLG‐NS, it was 10.1°C below. The mean Tg of GE/NC‐NS was determined to be 106.3°C, and in the glass transition as well as rubbery regions, it was observed to compete with the E′ value of the control GE composites. Fractography was done using micrographs obtained from environmental scanning electron microscope (ESEM). Traces of polymeric material found at the fiber surface certified the improved interfacial adhesion between glass fiber and polymer in the matrix‐modified composite samples. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced composites have attracted great, widely used specific industrial areas such as defense, aerospace, etc. However, composite plates are defenseless to damage accumulation such as matrix cracks, fiber delamination, and delamination, which limits the application of glass composites in specific industrial areas at limited strength levels. Therefore, analysis of the behavior of composites under the outof- plane loads is essential to optimize such material. This study examines the out-of-plane loading performance of multi-scale glass/epoxy composite laminate. To improve the load-carrying performance in the direction of out-of-plane, the halloysite nanotube (HNT) particle reinforcement was introduced to the epoxy matrix. The three-point bending tests were conducted to attain the out-of-plane load-carrying performance. The findings show that the flexural strength increases by almost 20% for the HNT-modified glass/epoxy composite compared to the unmodified counterpart; meanwhile, the toughness is effectively improved with the HNT addition. Moreover, the damage process of specimens in three-point bending tests was detected by microscopic examination. [ABSTRACT FROM AUTHOR]

The current study focuses on the investigation of the synergetic effect of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) on the flexural properties, hardness and water absorption characteristics of glass fiber reinforced polymer (GFRP) laminated composite materials. The laminated composite materials were fabricated with various configuration of filler reinforcements using vacuum assisted hand lay-up technique. Further, micromechanical analysis was performed using Halpin-Tsai model to investigate the synergistic effect of CNT/GNP hybrid glass fiber reinforced epoxy nanocomposites. It was observed that the CNT and GNP reinforced hybrid composite exhibited highest value of flexural strength and hardness; the respective values being 38% and 29% higher in comparison to the neat epoxy composite. Furthermore, among GNP and CNT, the composite containing former reinforcement exhibited better mechanical properties. The composites containing nanoparticles also exhibited better water uptake characteristic, where the weight gain for hybrid composite was 1.004%, whereas, for neat epoxy composite, the weight gain was 1.210%. This was attributed to the ability of nanofillers to restrict the intermolecular movement of the surrounding GFRP composites, which delays the relaxation of polymer chains, thereby reducing the diffusion of tiny molecules through the composites. It was also observed that the addition of GNPs has a strong effect on the elastic properties of the hybrid glass fiber reinforced epoxy nanocomposite than the addition of CNTs. [ABSTRACT FROM AUTHOR]

Natural fiber composites (NFC) exhibit good specific mechanical properties in comparison to synthetic fiber composites (SFC). The study investigates interlaminar glass (G) fiber hybridized jute (J) and flax (F) reinforced epoxy composites designated as JGGJ, GJJG, FGGF, and GFFG along with their virgin counterparts. Composite laminates of four plies are manufactured by hand-layup followed by compression molding to investigate tensile, flexural, and interlaminar shear properties. Further the effect of hybridization is also investigated for modal frequencies and damping ratio obtained from experimental modal analysis. Glass fiber hybridization as extreme layers shows significant improvement in flexural and shear properties as compared to tensile. Glass fiber reinforcement, as core layers improve the damping by 155.55% and 101.31% for JGGJ and FGGF, respectively, over pure glass epoxy. However with increase in bending stiffness of GJJG and GFFG, the bending modal frequency is improved. Also, the modal frequency and damping ratio increases following a power-law variation with a decrease in the free length. Finite element and analytical validations are presented to the experimental frequencies and flexural modulus, respectively. These studied hybrid composites can serve as semi-structural members like interior trim panels in automotive applications that possess significant strength and dissipate in-service vibrations effectively. [ABSTRACT FROM AUTHOR]

Hybrid multiscale fiber reinforced epoxy composite laminates were developed and characterized from woven glass fiber mats reinforced with nonwoven PAN nanofibers (diameters of 200 nm) produced via electrospinning. An electrospinning setup was designed and developed to produce continuous E‐spun nonwoven nanofiber (NWNF) mats, which were then used as interlaminar reinforcements for producing multiscale hybrid composites. A detailed study for producing E‐spun nanomats considering both solution and operation parameters was undertaken discussed and optimum spinning parameters were obtained. These parameters were used to produce the E‐spun NWNF mats, which were inserted into the interlaminar region of glass fiber reinforced epoxy laminates. The impact absorption energy, tensile strength, and flexural strength of the hybrid multiscale composites were found to increase with an increase in E‐spun NWNF mat weight fraction. These properties were compared to those of a conventional glass fiber composite laminates prepared from the neat epoxy resin with 32% glass fiber volume fraction. The effectiveness of the strengthening/toughening strategy formulated in this study indicates that the feasibility of using the E‐spun NWNF mat reinforcements for improving the mechanical properties of structured high‐performance composites. In addition, the present study provides motivation for the long‐term development of high‐strength high toughness bulk structural nanocomposites for broader engineering applications. [ABSTRACT FROM AUTHOR]

This work focuses on the study of variation in behaviour of Glass Fiber Reinforced Epoxy Composite laminate in the presence of healing agent filled microcapsules. Healing capacity was tested for the newly developed laminate with capsules. Two types of microcapsules were made and included in the resin system. One type consists of healing agent and other type consists of curing agent. These capsules were blended in the ratio of 10:3 in the resin system and laminate was fabricated by hand lay-up technique. Initially, the effect of microcapsules on the tensile properties of glass fiber epoxy composites was studied. No conspicuous variation was discerned in the tensile nature. The healing ability of the laminate was checked by producing minor indentation damage on the surface of the laminate with a 0.5 mm ball indenter. It was noticed that 80% of the indentation was recovered within the time span of 48 hours and 93% of healing efficiency was attained. FE analysis was performed with MIDAS NFX software to confirm the results. Both experimental and FE analysis results were observed to be identical. [ABSTRACT FROM AUTHOR]

The curing kinetics can influence the final macroscopic properties, particularly the three-point bending of the fiber-reinforced composite materials. In this research, the curing kinetics of commercially available glass fiber/epoxy resin prepregs were studied by non-isothermal differential scanning calorimetry (DSC). The curing kinetic parameters were obtained by fitting and the apparent activation energy Ea of the prepreg, the pre-exponent factor, and the reaction order value obtained. A phenomenological nth-order curing reaction kinetic model was established according to Kissinger equation and Crane equation. Furthermore, the optimal curing temperature of the prepregs was obtained by the T-β extrapolation method. A vacuum hot pressing technique was applied to prepare composite laminates. The pre-curing, curing, and post-curing temperatures were 116, 130, and 153 °C respectively. In addition, three-point bending was used to test the specimens' fracture behavior, and the surface morphology was analyzed. The results show that the differences in the mechanical properties of the samples are relatively small, indicating that the process settings are reasonable. [ABSTRACT FROM AUTHOR]

In this study, conductive carbon nanofibers (CNFs) were dispersed into epoxy resin and then infused into glass fiber fabric to fabricate CNF/glass fiber-reinforced polymer (GFRP) laminates. The electrical resistance and strain of CNF/GFRP laminates were measured simultaneously during tensile loadings to investigate the in situ strain and damage monitoring capability of CNF/GFRP laminates. The damage evolution and conduction mechanisms of the laminates were also presented. The results indicated that the percolation threshold of CNFs content for CNF/GFRP laminates was 0.86 wt % based on a typical power law. The resistance response during monotonic tensile loading could be classified into three stages corresponding to different damage mechanisms, which demonstrated a good ability of in situ damage monitoring of the CNF/GFRP laminates. In addition, the capacity of in situ strain monitoring of the laminates during small strain stages was also confirmed according to the synchronous and reversible resistance responses to strain under constant cyclic tensile loading. Moreover, the analysis of the resistance responses during incremental amplitude cyclic tensile loading with the maximum strain of 1.5% suggested that in situ strain and damage monitoring of the CNF/GFRP laminates were feasible and stable. [ABSTRACT FROM AUTHOR]