Search

In this study, two types of composites, polybutylene terephthalate (PBT) and epoxy resin (ER), reinforced with 20% of glass fiber (GF) are used as the comparative research objects. Their mechanical properties after thermal aging at 85~145 °C are evaluated by tensile strength and fracture morphology analysis. The results show that the composites have similar aging laws. The tensile strength of GF/PBT and GF/ER decrease gradually with the increase of aging temperature, while their elastic moduli are independent of the thermal treatment temperature. Scanning electron microscopy study of the fracture surface shows that separation of glass fiber from PBT and ER matrix becomes more obvious at higher aging temperature. The fibers on the matrix surface appear clear and smooth, and the whole pulled out GFs can be observed. As a main mechanical strength degradation mechanism, the deterioration of interface adhesion between the matrix and GF is discussed. A large difference in coefficients of thermal expansion of the matrix and GF is a main factor of the mechanical degradation. [ABSTRACT FROM AUTHOR]

This research aims to develop fiber-reinforced composites (FRC) with enhanced fire resistance, which can be particularly useful for the transport industry (e.g., aviation, automotive, and train production). The fire retardation was achieved through epoxy matrix modification with hexachlorocyclotriphosphazene (HCTP). First, the fire-resistant and mechanical properties of the epoxy matrix filled with different HCTP contents (4.8, 7.2, and 9.5 wt.%) were studied to select the most effective HCTP content for the impregnation of FRC. Then, glass, basalt, and carbon fiber fabrics were impregnated with epoxy filled with 7.2 wt.% of HCTP, and the fire resistance, flexural, and interlaminar fracture properties were studied to select the most effective HCTP-modified type of fiber reinforcement based on the test results. It was concluded that basalt fiber impregnated with epoxy filled with HCTP could be selected as the most effective reinforcement type, allowing excellent mechanical and flame-retardant properties. [ABSTRACT FROM AUTHOR]

This paper presents a study regarding the obtaining, characterizing and mechanically testing a new laminar composite material, consisting of epoxy resin reinforced with basalt plain fabric. The composites were obtained by manual lay-up, cross-link stage being developed by pressure molding in a hydraulic press. Rectangular plates were obtained and cut into samples with specific shapes, for the mechanical tests (tensile, three-point bending and compression). After testing, the fracture zone was analyzed using optical microscopy to observe the behavior of the composite following the mechanical stresses applied (fracture mechanism, voids presence and fiber delamination identification). Due to the low costs and non-hazardous nature, basalt fibers can be a serious competitor in the production of laminar composites that could successfully replace ordinary glass fiber composites. The mechanical properties in tensile, three-point bending, and compression of epoxy-resin-impregnated basalt fiber composites are comparable and even exceed those of widely used epoxy-resin-impregnated fiberglass composites. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer composites are manufactured using various methods, with vacuum-assisted resin transfer molding (VARTM or VARIM). This study's primary focus lies in assessing how the orientation of sampling impacts the mechanical properties of glass fiber-reinforced pure and nanocomposites. 2 wt.% nano Al2O3- doped and non-doped composites were produced using the VARTM process. Tensile, flexural, and density test specimens were extracted from three distinct zones and two distinc direction those aligned horizontally to the resin flow (HRF) and those oriented vertically to the resin flow (VRF). Remarkably, results showed up to a 3.91% increase in values from samples in the third zone, particularly on the vacuum outlet side. To facilitate precise stress value comparisons across plates, uniform sample orientation and consistent zone selection are essential. [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]

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]

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 intention of this research is to recapitulate the two different fillers like E glass fiber and nanocarbon fiber, which were utilized to fabricate the polymer matrix composites by the assistance of epoxy resin. The mechanical compression molding was influenced to produce the polymer-based nanocomposites under consideration of optimal process parameters. There are three different weight fractions E glass fiber (40%, 45%, and 50%), nanocarbon fiber (10%, 15%, and 20%), and epoxy concentrations (30%, 40%, and 50%), respectively, that were used to produce the polymer matrix composites. Those processing parameters were designed by the L9 Taguchi with DOE technique to conduct the mechanical tests like tensile strength and hardness properties. The signal-to-noise ratios were successfully accomplished to identify optimal process parameters for improving the individual responses. The ANOVA and interaction was additional supports to enhance the mechanical properties. The scanning electron microscope was used to examine the fracture surfaces at the tensile fracture specimens with optimal conditions. Moreover, the maximum mechanical characteristics were attained by the increasing of nanocarbon fiber in the processed polymer matrix composites. [ABSTRACT FROM AUTHOR]

In the current study, the nano-composites of unidirectional carbon and glass fiber reinforcedepoxy resin with multi-walled carbon nanotubes (MWCNTs) were separately prepared by hand lay-up and hot pressing of fiber epoxy prepregs. Three types of MWCNT derivatives (parentCNT, low carboxylated CNT (LCCNT) and higher carboxylated CNT (HCCNT)) were dispersed into the epoxy resin/fiber composites. The improved mechanical properties observed in the three component composites could be attributed to the uniform dispersion of CNTs in epoxy/ fiber matrices, nanosize of the additives and the improved interfacial interactions between the composite components. The COOH functional groups could also be effective in the increase of mechanical traits because they induce the amphiphilic nature into CNTs for better dispersion and to generate the better glass fiber/epoxy (E/G) and carbon fiber/epoxy (E/C) interactions. HCCNT led to the best mechanical properties among all the samples due to its higher carboxyl content. HCCNT also changed the curing peak of epoxy in DSC and improved its thermal stability. For instance, the final residual mass for E/HCCNT was 15.4% at 600 °C compared to 13.92% for the pure epoxy while the values of 17.55 and 16.48% were observed at 500 °C for E/HCCNT and epoxy, respectively. The observed effect of COOH functionality on the void formation within the composite and on the better CNT dispersion in the matrix can be considered as an important observation for investigating the E/C/CNTs nanocomposites. [ABSTRACT FROM AUTHOR]

This paper presents the behavior of composite panels based on glass fiber unidirectional fabrics and a bi-component epoxy resin under ballistic impacts that characterize two threat levels: FB2 and FB3, according to EN 1523:2004. The tested panels had characteristics kept in narrow ranges: thickness 18.26 ± 0.22 mm, mass ratio fabrics/panel 0.788 ± 0.015, surface density 27.51 ± 0.26 kg/m2. After testing the panels, the failure mechanisms of the panel were evidenced by scanning electron microscopy and photographs. Here the authors present a finite-element model at meso scale that was used for evaluating if the composite, initially tested at level FB2 (9 mm FMJ, v0 = 375 m/s), could withstand the higher level of impact, FB3 (projectile type 0.357 Magnum and impact velocity of v0 = 433 m/s). Simulation was performed in Explicit Dynamics (Ansys), keeping the same target but changing the projectile for the two different levels of threat. The results of the simulation were encouraging for making tests at level FB3, indicating the importance of alternating actual tests with simulations in order to achieve better protection with reduced surface weight. The simulation illustrated differences in impact duration and number of layers broken on the panel for each level. Validation of the model was based on the number of broken layers and the dimension of the delamination zone between the last two layers. Scanning electron microscopy was used for identifying failure mechanisms at the micro and meso scale. We found that damage to the composite was intensively dependent on impact velocity, this being quantitatively evaluated using the number of layers broken, the effect of delamination on separating layers and the deformation of the last layer. [ABSTRACT FROM AUTHOR]

To improve the thermal and mechanical properties of epoxy resins, epoxy-functionalized POSS (E-POSS) and glass fiber (GF) were used to reinforce epoxy resin (E51) composites. The tensile, thermo-mechanical, fractured, and thermal tests were carried out to characterize these hybrid materials. The results show that E-POSS and GF could significantly improve the mechanical and thermal properties of epoxy resins due to high crosslink density of resin matrix and synergistic interaction between the epoxy resin, E-POSS, and GF. Compared with the pure E51 resin, the tensile strength of the E51 + E-POSS (10%) + GF (16%) sample increased by 257.6%, and the thermal decomposition temperature (Td5%) of the E51 + E-POSS (10%) + GF (16%) sample increased by 32 °C to 378 °C. [ABSTRACT FROM AUTHOR]

The addition of fillers to polymer composites induces a positive influence on the mechanical and tribological properties of the hybrid composites. These properties can be validated for possible uses such as automobile, construction, shipping, aerospace, sports equipment, electronics, and biomedical domains. In the present research, epoxy matrix reinforced with nylon-6 fibers and glass fibers were prepared using the solution blend technique. Alumina nanoparticles are added as fillers to enhance the properties of epoxy hybrid composites. The large surface area of interaction of nanofillers exhibits better adhesion between matrix and fibers of composites, and it significantly affects the various properties of composites. The tribological characteristics of fabricated epoxy hybrid composites were evaluated under various parameters and conditions. The results revealed that the addition of nanofiller significantly reduces the wear loss of epoxy hybrid nanocomposites. The wear resistance of epoxy hybrid composites increased with increase in addition of nanofiller up to 1.0%, and it slightly decreased with the further addition of filler. The Taguchi analysis was carried out for the least coefficient of friction and specific wear rate. The analysis found that the specific wear rate and coefficient of friction mainly depend on load, followed by speed and nanofiller. The fractured and worn surface of Al2O3-filled epoxy hybrid composites was analysed using SEM. [ABSTRACT FROM AUTHOR]

To further improve the preparation efficiency and properties of bamboo fiber reinforced polymer composites (BFRPs) fabricated by the vacuum-assisted resin transfer molding (VARTM) process. Here, the bamboo fiber/glass fiber mesh reinforced polymer hybrid composites (BGRPs) were fabricated by VARTM to determine the effects of three fiber stacking sequences (namely, GBBGBBG, BGBGBGB, and BBGGGBB; B: bamboo fiber, G: glass fiber mesh) on the physical and mechanical properties, as well as void characteristics of BGRPs (i.e. BGRP-1, BGRP-2, and BGRP-3). The results showed that the incorporation of glass fiber meshes could shorten the injection time of epoxy resin and improve the mechanical properties of BFRPs. BGRP-1 exhibited the lowest water absorption (1.31%) and the highest shear strength (15.55 MPa). Glass fiber meshes on the surface and bottom of BGRP-1, respectively, served as buffer layers to retard mechanical damage, so that BGRP-1 had the best drop hammer impact properties. BGRP-2 represented the highest flexural strength and flexural modulus of 92.22 MPa and 6.69 GPa, respectively. The mechanical properties of BGRP-3 were inferior to those of BGRP-1 and BGRP- 2, and more voids were observed in the middle of BGRP-3 in micro-CT slices induced by inadequate epoxy resin impregnation on bamboo fibers. [ABSTRACT FROM AUTHOR]

Investigations into polymer composites are mainly focused on properties dependent on glass fiber reinforcement and particulate fillers. In the present study, the effect of the binder was examined. The specimens were produced with two types of epoxy resin, with similar numbers of glass mat layers and similar proportions of quartz powder added. However, one group was fabricated with an emulsion binder in the glass mats and another group with a powder binder. Attention was concentrated on the tribological properties of the as-prepared composites, though their strength was examined as well. The hardness of the Sikafloor matrix was found to be much more sensitive to the applied binder than that of the MC-DUR matrix. No direct correlation between the microhardness and the specific wear rate was observed and increasing the particulate filler proportion did not cause a direct increase of the specific wear rate. In particular, the highest specific wear rate, around 350 J/g, was reached for both matrices with a 1% quartz addition when the emulsion binder was applied, while in the case of the powder binder it was with 6% quartz with the MC-DUR matrix, and there was no quartz addition with the Sikafloor matrix. The highest microhardness, HV0.5 = 25, in turn, was reached for the mats with the emulsion binder in the Sikafloor matrix with an addition of 10% quartz powder, while the highest friction coefficient was exhibited in the composite with the MC-DUR matrix, when 1% of the quartz powder and the emulsion binder were applied. [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]

Reinforcing fibers, nanofillers, matrix materials, and manufacturing techniques all have a role in the mechanical characteristics of hybrid composites. MWCNTs-reinforced E-glass/Kevlar/epoxy composites are appropriate fillers for structural applications. The impact of different concentrations of MWCNT fillers (0.4%, 0.8%, and 1.2% wt) on the mechanical characteristics of hybrid composites has been studied. Tensile and bending strength, as well as hardness, were measured in compression-molded composites. The effects of compression pressure, mold temperature, and applied pressure on hybrid (0.8% MWCNT) were investigated. When it came to composite tensile and bending strength, compression pressure was the most important factor, closely succeeded by mold temperature and pressure period. Compression molding were optimized, resulting in a tensile strength of 183 MPa, a bending strength of 158.3 MPa, and a hardness value of 23.8 HV. [ABSTRACT FROM AUTHOR]

Water invasion induced aging and degradation of the unidirectional glass fiber reinforced epoxy resin (UGFRE) rod is inferred as the primary reason for the decay-like fracture of the composite insulator. In this paper, the moisture diffusion processes in the UGFRE from different directions at various test humidities and temperatures are studied. The moisture diffusion of the UGFRE sample obeys the Langmuir diffusion law under the humidity conditions of 53%, 82% and 100% at 40 °C. In deionized water, the moisture diffusion of the UGFRE sample also obeys the Langmuir diffusion law when the invading direction is vertical to the glass fiber. However, when the water invades the UGFRE sample, parallel with the glass fiber, the weight loss caused by composite degradation should not be neglected. A modified Langmuir model, taking Arrhenius Theory and the nonlinear aging characteristic of the composite into consideration, is proposed and can successfully describe the moisture diffusion process. Both the glass fibers and epoxy resin will degrade in the deionized water. The glass fibers show better resistance to degradation than the epoxy resin. The epoxy resin degrades from the glass fiber/epoxy resin interface and become fragments. For composite insulators, the water invasion through the ends should be avoided as far as possible, or the degradation of the UGFRE rod will result in decay-like fracture. [ABSTRACT FROM AUTHOR]

The present study is focused on investigating the mechanical properties of hybrid polymer composites. The reinforcement materials are animal bone (ox) particulate and E-glass fiber. The matrix material is epoxy resin. The following combinations are considered for investigation: (a) bone particulate weight percent (20%, 30%, and 40%), (b) E-glass fiber weight percent (20%, 30%, and 40%), and (c) bone particulate (10%, 20%, and 30%) and E-glass fiber (30%, 20%, and 10%) with epoxy resin 60% by weight percent. The test specimens are prepared as per the required ASTM standard for tensile, compressive, and flexural tests. The test results show that maximum tensile and compressive strength observed in 40% of E-glass fiber with 60% of epoxy matrix, correspondingly, is 254.964 MPa and 37.52 MPa. The maximum flexural strength observed in E-glass fiber reinforced composites is 250.43 MPa. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymer (FRP) composites possess excellent specific strength, specific stiffness and controlled anisotropy for which these are extensively used in various engineering applications, like automobile industries, aerospace industries, marine industries, space industries, electronics industries and many more. Glass fibers (GF), carbon fibers (CF) and aramid fibers (AF) are common reinforcements for polymer matrix composites (PMCs). High mechanical properties and wear resistance behaviour of glass fiber reinforced composites are the premises for the current experimental research on the effect of fiber orientation on the tensile strength of the polymeric composite materials. The glass fiber reinforced epoxy resin composite was prepared by wet lay-up method, followed by thermal treatment. [ABSTRACT FROM AUTHOR]

Nanodiamonds (NDs) are the potential fillers to provide excellent mechanical and multi-functional capabilities. The growing interest in using NDs in a variety of fields has prompted researchers to use NDs to prepare various structural composites. Proper dispersion and interfacial adhesion between the NDs and the polymer matrix are required to use NDs as effective reinforcement in polymer nanocomposites. In this study, the mechanical properties of the epoxy-based glass fiber (GF)- and carbon fiber (CF)-reinforced laminated composites with the incorporation of annealed nanodiamonds (NDs) in the epoxy matrix was analyzed. The epoxy resin was modified through the step-wise addition of annealed NDs from 0.1 to 0.5 wt.%. The surface-modified NDs were characterized by SEM, XRD, FTIR, and TEM. The test results predict that the tensile strength was increased by 25, 23%, and tensile modulus increases by 33, 135% for GF- and CF-reinforced hybrid composites corresponding to the addition of 0.3 wt.% NDs into the epoxy matrix. Also, the flexural strength increased by 36, 37%, and flexural modulus increased by 71, 37% for the GF- and the CF-reinforced hybrid composites corresponding to the addition of 0.3 wt.% NDs into the epoxy matrix. These improved properties of hybrid composites are mainly due to the enhanced mechanical interlocking and weak Van der Waals force between the NDs particles that caused the efficient dispersion of NDs in the epoxy matrix and it has been reported in this study. [ABSTRACT FROM AUTHOR]

Recently, the utilization of hybrid basalt/glass fiber reinforced polymer (HBGFRP) nanocomposites has increased significantly in structural applications due to their light weight nature, superior strength-to-weight ratio, and excellent mechanical, chemical, and thermal properties. This study aims to investigate the effects of various drilling parameters and filler weight content on delamination and surface roughness on HBGFRP nanocomposites filled with combination of multi-walled carbon nanotubes (MWCNTs) and nano-silica particles (SiO2) in equal weight proportions of 0%, 1%, and 2%. These nanocomposite laminates were fabricated using the manual lay-up method followed by compression molding with a novel stacking order of fibers 01B/02G/02B/02G/02B/02G/01B consisting of 12 layers.. In this work, the Box-Benkhen Design of Response Surface Methodology (RSM) was employed to optimize the drilling parameters, including spindle speed, feed rate, drill diameter, and weight content of MWCNTs + SiO2. The nanocomposites containing 1.0wt. % MWCNTs + SiO2 demonstrated the most significant reduction in the delamination factor, achieving a 24% reduction. The lowest delamination factor recorded was 1.29, obtained with a spindle speed of 1350 rpm, a feed rate of 0.1 mm/rev, a drill diameter of 6 mm, and the addition of 1.0wt. % MWCNTs + SiO2. Increasing the spindle speed resulted in a further reduction in the delamination factor. The surface roughness measured was 1.213 µm, indicating a relatively smooth surface. It was evident that increase in feed rate and drill diameter corresponded to increase in both delamination factor and surface roughness. [ABSTRACT FROM AUTHOR]

In this study the experimental investigation of mechanical behaviour of Multi-Walled Carbon nanotubes (MWCNTs) and Aluminium Oxide (Al2O3) reinforced with EGlass/ Epoxy nanocomposites at 0.5%, 1.5% and 2.0% of weight rated with 225 GSM, 300 GSM and 450 GSM glass fibres were studied. Test specimens were prepared at the standardof ASTM D638 for tensile specimen ASTM D256 for impact specimen. Testspecimens were prepared at the ratio of MWCNTs: Al2O3 is 1:4. 1.5 wt. % of Multi- Walled CNTs filledE-Glass/Epoxy nanocomposites showed improved mechanical properties than glass fiber reinforced epoxy composites.450 GSM reinforced glass fiber epoxy composites containing 1.5wt. % of MWCNTs improved 36.27 % of higher tensile value and 28.57 % of impact value than the glass fibre reinforced epoxy composites. 225 and 300 GSM reinforced glass fibre epoxy composites with 1.5 wt. % of MWCNTs composites also has improved tensile and impact value than glass fibre reinforced epoxy composites. But, overall 450 GSM reinforced fibre nanocomposites showed enhanced mechanical properties than the other GSM reinforced nanocomposites. This proves Multi- Walled Carbon Nanotubes is a successful reinforcement for E-Glass/Epoxy matrix and it improves its properties and performance. [ABSTRACT FROM AUTHOR]

Abstract Ramie fiber in combination with glass has proved to be excellent for making cost effective composite materials. They are prepared by hand layup method using E-glass and ramie fibers. The resin used in the preparation of composites was epoxy. Fiber reinforced composites were hybridised at two weight percentages (20% and 30%). Samples prepared were tested to evaluate its properties, such as tensile strength, flexural strength, impact strength, and scanning electron microscope (SEM). Scanning electron microscope analysis revealed the morphological features. HFREC (Hybrid fiber reinforced epoxy composite) exhibited better mechanical properties than the individual samples. [ABSTRACT FROM AUTHOR]

Abstract Owing to the outstanding properties of nano-Al 2 O 3 particles have incited material researchers to have a promising invasion in the field of fibrous polymeric composites. There is an uncertainty of nano-Al 2 O 3 /polymer interfacial stability at high temperature engineering applications. Current investigations explicate the effects of nano-Al 2 O 3 content on the mechanical behavior of glass/epoxy (GE) composites at various in-situ elevated temperatures. The flexural properties and viscoelastic behavior of the composites have been investigated and evaluated. The Weibull design parameters were analysed as a function of nano-Al 2 O 3 content and different test temperatures. Scanning electron microscopy analyses were carried out to understand various interfacial strengthening mechanism and micro-mechanism failures. These results indicated that incorporation of 0.1 wt% of nano-Al 2 O 3 in GE composites at room temperature could be considered an optimal value in flexural strength enhancement. The fracture surfaces demonstrated a combination of fiber pullout, interfacial debonding, matrix drainage and fiber imprints failure morphologies. Weibull analyses responded a reasonable agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract Flax composites demonstrate superior damping properties to conventional fibres. These materials are already being utilised in some products but the mechanical properties they exhibit are too low for many structural applications. Hybridization of flax with higher strength fibres has been shown to yield materials, which balance damping and load carrying capabilities alongside improved environmental credentials for flax/carbon hybrids. However, the most used composite material is E-glass but the current literature does not facilitate the prediction of damping properties for these hybrid composites, where it is expected that they will behave differently due to the difference in material properties. The woven flax and E-glass fibres specimens embedded with epoxy resin are manufactured via resin infusion to understand the damping and mechanical properties possible from an industrial process and the dominant factors affecting them, rather than the relationships between individual variables and these properties. These experiments allow the hybrids to be profiled for the first time and it is observed that hybridization of flax and E-glass fibres results in an increase in damping, from 1.97% to 2.63% for the best hybrid, especially when the flax plies are placed on the outer skin, however the compromise in tensile properties is significant, from 473.28 MPa to 166.53 MPa. [ABSTRACT FROM AUTHOR]

Abstract Fiber reinforced sandwich composites are frequently used today. The inability to recycle these frequently used materials ensured that the repairs of these materials became more important. There are a several different methods developed on this area, but most of them are basically based on the patch repair method. In this study it is aimed to improve the efficiency of repair with newly proposed patch types to be applied during the patch repair process, which is used in the repair of sandwich composites. Sandwich composite plates were made of glass fiber, PVC foam and epoxy resin with vacuum assisted resin infusion method. Prepared specimens were subjected to the three-point bending test taking into consideration parameters such as specimen width, damage diameter and the results were evaluated. As a result, it has been seen that the proposed methods significantly affect the efficiency of patch repair. Highlights • This study aimed to improve the efficiency of sandwich composite repair with newly proposed patch types. • Improvement studies were carried out to repair a damaged sandwich composite using the minimum number of repair plies. • Patch type repair method was applied and three different types of patches are proposed on this method for improving strength. • All specimens were subjected to three-point bending tests under the parameters of specimen width, damage diameter. • As a result, the quality of the repairs has got improved with the modifications which applied to the patch type repair. • Load carrying capacity of developed methods increased the repair strength according to the conventional patch repair method. [ABSTRACT FROM AUTHOR]

The interfacial properties for three different glass fiber (GF) mats were evaluated by examining permeability through combining the results of wettability and interlaminar shear strength (ILSS) testing. Three types of GF mats were studied: (1) unidirectional (UD), (2) bidirectional (BD, 0/90°), and (3) randomly-chopped (RC). Single fiber tensile tests were used to compare the fibers in the 3 mats, forty single fibers were extracted from each mat. FE-SEM was used to study damages on the GF in each of the mat types. Fibers from the UD mat exhibited the best mechanical properties and less damage was observed with the FE-SEM. Vacuum assisted resin transfer molding (VARTM) was used to manufacture glass fiber reinforced composite (GFRC) specimens, with the three different mat types. The permeability of the different GF mats was measured, during manufacture of the GFRC, and related to the spreading of the epoxy resins in the GF mats. Short beam tests were performed as a measure of interfacial properties and related to the observed permeability and spreading. GFRC manufactured with UD GF mat exhibited the best interfacial and mechanical properties and displayed the least physical damage while GFRC manufactured with BD GF mat had the poorest interfacial and mechanical properties while exhibiting the most visible damage. The UD GF mat also displayed the smallest change in contact angle and the best permeability. The longitudinal fiber pattern in the UD GF mat apparently promotes capillary effects leading to an increase in wetting rate. This study demonstrates that GF mat pattern affect the interfacial and mechanical properties as well as matt permeability and resin spreading. [ABSTRACT FROM AUTHOR]

The paper deals with analysis of relationships between the microgeometry and mechanical properties of fiberglass i.e. epoxy resin composites with random fibers distribution. The mechanical properties (e.g. a flexural modulus E f , taking into account shear effects) of the material were determined in bending by Short Beam Shear Tests (SBST). Microgeometry of the structure was characterized on the basis of microscopic images of test specimens. The paper proposes a new measure of irregular reinforcement distribution expressed as an area ratio of the matrix surrounding the single fiber to the circuit of the fiber. The measure, denoted by G AB , is expressed in microns. In particular the relationship between the results obtained in the test samples with random distribution of fibers and theoretical regular structures of square (K) and hexagonal (H) type is presented. Specimens of the investigated composite (E-glass fibers and Epidian 5 epoxy resin), supplied by industrial partner, were cut out from raw material of helicopter blades girders. The obtained experimental results for the analyzed composite corresponded to approximation by the theoretical model of the square (K) type. The results can be used to estimate the flexural elastic modulus E f of the unidirectional composites with irregular arrangement of fibers, made manually or using the molding apparatus. Based on those results, it can be concluded that the square distribution model (K) is appropriate for numerical estimation of the strength composites properties reinforced with glass fibers of circular cross-section, having the diameter in the range of 10–16 μm. [ABSTRACT FROM AUTHOR]

This study aims to improve the web crippling performance of pultruded glass fibre-reinforced polymer (GFRP) C sections using fibre-reinforced epoxy composite (FEC). The strengthened GFRP C sections were subjected to two loading conditions: interior-two-flange (ITF) and exterior two-flange (ETF). The parameters considered were bearing lengths, FEC strengthening length and thicknesses. Two failure modes, namely web-flange junction failure and web buckling failure were observed for the pultruded GFRP C sections under ETF loading conditions as the bearing length changed. While the combination of the web-flange junction and FEC crushing failures were observed under ITF loading conditions at 20 mm and 50 mm bearing lengths. Furthermore, the average web crippling capacity of strengthened GFRP C sections improved by up to 426 % and 488 %, in comparison to control samples under ETF and ITF loading conditions, respectively. The average web crippling capacity of pultruded GFRP C sections increased up to 45 % when the bearing length increased from 20 mm to 50 mm. The finite element (FE) outcomes showed an agreement with experimental results in the context of failure patterns, load-displacement profiles and web crippling capacities. Finally, equations were proposed to estimate the web crippling capacity of pultruded GFRP C sections strengthened with FEC. [ABSTRACT FROM AUTHOR]

While conventional fiber-reinforced polymer composites offer high strength and stiffness, they lack ductility and the ability to absorb energy before failure. This work investigates hybrid fiber composites for structural applications comprised of polymer, steel fiber, and glass fibers to address this shortcoming. Varying volume fractions of thin, ductile steel fibers were introduced into glass fiber reinforced epoxy composites. Non-hybrid and hybrid composite specimens were prepared and subjected to monolithic and half-cyclic tensile testing to obtain stress-strain relationships, hysteresis behavior, and insight into failure mechanisms. Open-hole testing was used to assess the vulnerability of the composites to stress concentration. Incorporating steel fibers into glass/epoxy composites offered a significant improvement in energy absorption prior to failure and material re-centering capabilities. It was found that a lower percentage of steel fibers (8.2%) in the hybrid composite outperformed those with higher percentages (15.7% and 22.8%) in terms of energy absorption and re-centering, as the glass reinforcement distributed the plasticity over a larger area. A bilinear hysteresis model was developed to predict cyclic behavior of the hybrid composite. [ABSTRACT FROM AUTHOR]

The effect of nanoclay addition in Glass Fiber Reinforced Epoxy (GFRE) composites on impact response was studied. The epoxy nanocomposite matrix with 1.5 and 3.0 wt% loading of I.30E nanoclay was produced by high shear mixing. Hybrid GFRE nanoclay composite plates were manufactured by hand layup and hot pressing techniques using electrical grade-corrosion resistant (E-CR) glass fiber mats. The laminates were then subjected to low-velocity impact with energies between 10 and 50 J. Addition of nanoclay was found to improve peak load and stiffness of GFRE. Nanoclay loading of 1.5 wt% resulted in optimum properties, with 23% improvement in peak load and 11% increase in stiffness. A significant reduction in physical damage was also observed for hybrid nanocomposite samples as compared to GFRE. This was mainly attributed to transition in damage mechanism due to nanoclay addition. Clay agglomeration in samples with 3.0 wt% loading contributed towards limiting the improvement in impact resistance. [ABSTRACT FROM AUTHOR]

In this work, flame-retardant glass fiber reinforced epoxy composites (FGRE) were successfully prepared via adding a novel phenylphosphonate-based flame retardant, N, N '-diamyl- p -phenylphosphonicdiamide (P-MA) into GRE. FGRE12 showed high LOI value of 33%. Meanwhile, FGRE12 passed V-0 rating in UL 94 test and the peak of heating release rate (pHRR) decreased by 54% in comparison with that of GRE. The flame-retardant efficiency of P-MA in GRE was compared with that in epoxy matrix (EP). Moreover, the influences of P-MA on mechanical and thermal stability properties of GRE were studied systemically. Dynamic mechanical analysis (DMA) studied the influence of P-MA on viscoelasticity of GRE. Fiber push-in test and three-point-bending test were used to evaluate the influence of P-MA on the EP matrix/fiber interface strength and interlamilnar shear strength, respectively. In addition, nanoindentation test was used to study the hardness and Young's modulus of EP matrix. The above results showed that the addition of P-MA did not affect the hardness of epoxy matrix and interfacial strength (epoxy matrix/glass fiber). The influence of P-MA on thermal stability of GRE was studied by thermalgravimetric analysis (TGA). These results would be very important in designing new generation multifunctional epoxy-based composite materials. [ABSTRACT FROM AUTHOR]

The goal is to study the effect of the SiO2 micro and nano – particles addition on the strength of epoxy composite based on glass fibers using (2, 4, 6 and 8) wt% of SiO2, the interlaminar fracture toughness (GIC) of 16-plies [M]16 of woven roving glass fiber /epoxy composites prepared by hand lay – up technique were investigated, using DCB test (mode I). The results computed using area method shows that the Interlaminar fracture toughness was increase with the filler content, higher values of GIC were observed for nano SiO2 composites as compared to microcomposites, because nano SiO2 behave as a barrier for crack propagation and the large surface density of these nanoparticles take a position in the polymeric chain restricting the movement for these chains leading to higher values of GIC in comparison with micro SiO2. The lower value of GIC found in 6 and 8 wt% is lower because, of the agglomeration of nano particles. This reflects the behavior of laminated nanocomposites into the same as microcomposites. [ABSTRACT FROM AUTHOR]

In this study, the interfacial and mechanical properties of cellulose nanocrystals (CNC) coated glass fiber/epoxy composites were investigated as a function of the CNC content on the surface of glass fibers (GF). Chopped GF rovings were coated with CNC by immersing the GF in CNC (0-5 wt%) aqueous suspensions. Single fiber fragmentation (SFF) tests showed that the interfacial shear strength (IFSS) increased by ~69% in composites produced with CNC coated GF as compared to uncoated GF, suggesting an enhancement of stress transfer across the GF/matrix interface. The role of CNC coatings on the tensile, flexural, and thermo-mechanical properties of the CNC-coated GF/epoxy composites was investigated. Incorporation of 0.17 wt% CNC in the composite resulted in increases of ~10% in both elastic modulus and tensile strength, and 40 and 43 % in flexural modulus and strength respectively. In conclusion CNC coatings on GF alter the GF/matrix interface resulting in improvement of the mechanical performance of the corresponding composites. [ABSTRACT FROM AUTHOR]

Electrospun glass nanofibers (EGNFs) are emerging fillers to improve mechanical properties of polymer matrix composite materials. However, questions concerning their reinforcing effectiveness in comparison with other nanoscale fillers such as glass/silica nanoparticles (GNPs) are still to be answered because reinforcing mechanisms for conventional fiber reinforced polymer composites might not be applicable at distinctive nanometer scale. Herein a comparative study on reinforcing effect of EGNFs and their conventional counterpart GNPs was carried out for the first time. Four types of glass nanofillers, including pristine EGNFs and GNPs as well as amino surface-functionalized EGNFs and GNPs were investigated to make epoxy matrix nanocomposites at ultra-low loading level (≤0.5 wt%). Mechanical properties of these glass nanofiller reinforced epoxy composites were investigated and corresponding reinforcing and toughening mechanisms at nanometer scale were discussed. Due to shape factor (aspect ratio), EGNFs demonstrated much more pronounced reinforcing and toughening effectiveness and completely outperformed GNPs in all cases despite much lower specific surface area. This research provided meaningful data to fully understand the merit of EGNFs as reinforcing filler in polymer nanocomposites and paved the road for designing and modeling next-generation polymer matrix composite materials. [ABSTRACT FROM AUTHOR]

This investigation describes the design, fabrication, and testing of woven glass fiber reinforced epoxy matrix laminates with aligned CNT sheets integrated between plies in order to improve the matrix dominated through thickness properties such as the interlaminar fracture toughness at ply interfaces. Using aligned CNT sheets allows for a concentration of millimeter long CNTs at the most likely point of laminate failure. Mode I and Mode II interlaminar fracture toughness of various CNT modified samples were investigated using double cantilever beam (DCB) and end notched flexure (ENF) experiments, respectively. Short beam strength (SBS) and in-plane tensile properties of the CNT modified samples were also investigated. Moderate improvement was observed in Mode I and Mode II fracture toughness at crack initiation when aligned CNT sheets with a basis weight of 0.354 g/m2 were used to modify the ply interface. No compromise in the in-plane mechanical properties of the laminate was observed and very little improvement was observed in the shear related short beam strength of the CNT modified laminates as compared to the control samples. Integration of aligned CNT sheets into the composite laminate imparted in-plane and through thickness electrical properties into the nonconductive glass fiber reinforced epoxy composite laminates. [ABSTRACT FROM AUTHOR]

Epoxy resins are widely used polymers, which are popular due to their workability, high tensile strength and a chemical resistance. The glass fibre fabric interlayer was used for improving the tensile and the quasi-.static lap shear strength of joints bonded with an epoxy adhesive. The aim of the experiment is to clarify a fatigue behaviour (low-cyclic tests of the fatigue) of structural two-component epoxy adhesive applied to a constructional steel S235J0. The fabric was composed from type E glass fibres in a plain weave. For optimization of properties of the composite bond it was used various weights in grams of the fabric in the extent of 80, 110, 160 g m-2 for the fabric treated by a wax, where this treatment is determined for better spinning of fibres at the production of the fabric, and weights of grams of 80, 110, 163 g m-2 at the fabric with a chemical dressing determined for improving the adhesion between the fibres and the epoxy resin. The specimens for quasi-static and lap shear strength tests were made in accordance with EN 1465:2009. The difference of the saturation of the various types of fabrics with the epoxy adhesive was observed with SEM (Scanning Electron Microscopy). It is obvious from the experiment results that it came to the improvement of the quasi-static loading at all adhesive bonds reinforced with glass fibres. The adhesive bonds specimens A110, A160, B110 and B160 resisted to required 200 cycles at 80% loading. The test specimens without the fabric showed worse properties. [ABSTRACT FROM AUTHOR]

In this paper, the results of experimental and numerical simulation of low velocity impact process have been carried out to investigate energy absorption of composite sandwich panels with 3D woven fabrics of glass fibers and epoxy resin. For this purpose, diagrams of force-displacement of the quasi-static and quasi-dynamic impact tests were studied. For the finite element simulation, Sandwich panel is considered as a composite material with anisotropic elastic properties. In this simulation, Hashin's damage criteria have been used to model the fracture mechanics. The energy absorption in quasi dynamic test is greater than the quasi static test. Comparison of numerical and experimental shows good agreement between the results. [ABSTRACT FROM AUTHOR]

The mutual exclusiveness between strength and toughness restricts the engineering application of glass fiber/epoxy composites requiring both high strength and suitable toughness. Inspired by natural nacre, a hetero-structural montmorillonite−multiwalled carbon nanotube (Mt−MWCNT) hybrid was coated on the curved surface of glass fibers to construct a nacre-like interface layer, consisting of Mt as "brick", MWCNTs as "anchor" and initial epoxy resin as "mortar". MWCNTs were employed for guaranteeing the effective separation of Mt nanosheets and strong interfacial interactions among the Mt, matrix and fiber. The enhanced dispersion degree of Mt−MWCNT hybrids and strongly bonded interface layer were established, and synergistic effects of Mt and MWCNTs on the strength and toughness of composites were also demonstrated. Compared with pure glass fiber/epoxy composite, interlaminar shear strength and work of break of resulting composites were improved by approximately 28% and 189%, respectively; meanwhile, such composite exhibits higher storage modulus in the glassy region and superior thermal stability. This work demonstrates a practical and effective strategy for fabricating high-performance yet low-cost fiber-reinforced composites through the nature-inspired interface. [Display omitted] • A nacre-inspired interface layer consisting of Mt as "brick", MWCNTs as "anchor" and epoxy resin as "mortar" was constructed. • A "Mt-MWCNTs/epoxy" interface layer was designed to efficiently reinforce GF/EP composites. • The simultaneous improvements in both strength and toughness were obtained for GF/EP composites. [ABSTRACT FROM AUTHOR]

The optimum condition of glass fiber/epoxy composites was investigated according to mixing ratio of two epoxy matrices. Novolac type epoxy and isocyanate modified epoxy were used as composites matrix. Based on chemical composition of mixing matrix, optimum mixing ratio of epoxy resins was obtained through FT-IR instrument. In order to investigate thermal stability and interface of epoxy resin, glass transition temperature was observed by DSC instrument, and static contact angle was measured by reflecting microscope. Change of IR peak and T g was conformed according to different epoxy mixing ratios. After fabrication of glass fiber/epoxy composites, tensile, compression, and flexural properties were tested by UTM by room and high temperature. The composites exhibited best mechanical properties when epoxy mixing ratio was 1:1. [ABSTRACT FROM AUTHOR]

Inspired by biological systems in which damage triggers an autonomic healing response, a polymer composite material that can heal itself when cracked has been developed. In this work, compression and tensile properties of a self-healed fibre reinforced epoxy composites were investigated. Microencapsulated epoxy and mercaptan healing agents were incorporated into a glass fibre reinforced epoxy matrix to produce a polymer composite capable of self-healing. The self-repair microcapsules in the epoxy resin would break as a result of microcrack expansion in the matrix, and letting out the strong repair agent to recover the mechanical strength with a relative healing efficiency of up to 140% which is a ratio of healed property value to initial property value or healing efficiency up to 119% if using the healed strength with the damaged strength. [ABSTRACT FROM AUTHOR]

Mesoscale models have been successfully used to simulate impact on fabrics and composites at ordnance velocities. There are many advantages of the mesoscale models: 1) individual components of the model (e.g. yarns) can be easily tested to check if they capture the important physics of the problem, 2) the components of the model often have simple material models (e.g. a yarn is often linear elastic up to failure), and 3) a multi-tier validation with material and ballistics tests at meso- and macroscale levels can be performed. The authors have successfully developed mesoscale models for a glass fiber reinforced composite (S-2 glass fiber with epoxy resin) that were validated by unconventional composite tests (e.g., torsion, out-of-plane delamination). In this paper the models are exercised at impact velocities ranging from 2 to 5 km/s. The original material models have simple constitutive laws (linear-elastic and elasto-plastic) that, in principle, have limited validity for hypervelocity impact. Therefore, modifications are made to better model the high-rate behavior of the epoxy resin matrix. The simulation results capture complicated damage mechanisms that might provide insight into future experimental data. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental research on unstrengthened and strengthened laminated veneer beams subjected to 4-point bending. Aramid, glass and carbon sheets with high tensile strength (HS) and ultra-high modulus of elasticity (UHM) glued to external surfaces with an epoxy resin adhesive were used as reinforcement. Two reinforcement layouts were used: (1) sheets glued along the bottom surface and (2) sheets glued to the bottom and side surfaces. Based on the test results, the flexural strength, flexural ductility and stiffness were estimated. Compared to the reference beams, the maximum bending moment was higher by 15%, 20%, 30% and by 16%, 22% and 35% for the Aramid Fiber Reinforced Polymers (AFRP), Glass Fiber Reinforced Polymers (GFRP) and Carbon Fiber Reinforced Polymers (CFRP) HS sheets, respectively. There was no significant increase in the flexural bending capacity for beams reinforced with UHM CFRP sheets. Similar values of bending ductility indices based on deflection and energy absorption were obtained. Higher increases in ductility were observed for AFRP, GFRP and CFRP HS sheets in "U" reinforcement layout. The average increase in bending stiffness coefficient ranged from 8% for AFRP sheets to 33% for UHM CFRP sheets compared to the reference beams. [ABSTRACT FROM AUTHOR]

• Epoxy/vinyl ester interpenetrating polymer network showed a significant improvement in the mechanical performance of GFRP composites w.r.t. GE and GVE composites. • The highest creep resistance of the GEVIPN composite was observed at a reference temperature of 30 °C. GEVIPN composite exhibited superior flexural performance at 30 °C but showed poor properties at 90 °C, over GE and GVE composites. GEVIPN composite exhibited a better damping ability as compared to GE and GVE composites. • Interfacial strengthening and weakening mechanisms of experimented composites are demonstrated. Fiber reinforced polymer (FRP) composites have become promising materials of modern times and find numerous applications in critical engineering fields including aerospace, marine and automobile sector. Due to their increasing demand, it becomes apparently essential to employ advanced techniques, which can predict the long-term behavior of such materials in various in-service conditions. Epoxy and vinyl ester based composites are most commonly used in structural FRP composites. As each polymer has its own advantages and disadvantages, hybridization or blending of different polymers is a trending technology to improve the performance of resulting FRP composite. The present article aims at comparing the performance of glass fiber reinforced epoxy-vinyl ester interpenetrating polymer network (GEVIPN) composite with that of the base materials, i.e. glass fiber reinforced epoxy (GE) and glass fiber reinforced vinyl ester (GVE) composites. Flexural testing has been conducted at various in-situ temperatures (30 °C, 60 °C and 90 °C) where GEVIPN composite showed highest properties at 30 °C. The lifetime prediction of the composite materials has been carried out using accelerated deformation and time-temperature superposition (TTSP) principle. It was observed that GEVIPN composite showed highest creep resistance as compared to the other two composites at lower temperature, whereas opposite trend was observed at elevated temperature. At 30 °C, GEVIPN composite showed positive reinforcement efficiency for ∼385 days with respect to GE and ∼46.27 years with respect to GVE. Similar studies were done for the other reference temperatures. Following this, fractography analysis of the fractured surface was done under FESEM to identify the failure mechanisms and draw a comparison between the composites. [Display omitted] [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]

This paper investigates the influence of silica nanoparticles on the mechanical properties of a unidirectional (UD) kenaf fiber reinforced polymer (KFRP) and hybrid woven glass/UD kenaf fiber reinforced polymer (GKFRP) composites. In this study, three different nanosilica loadings, i.e., 5, 13 and 25 wt %, and untreated kenaf fiber yarns were used. The untreated long kenaf fiber yarn was wound onto metal frames to produce UD kenaf dry mat layers. The silane-surface-treated nanosilica was initially dispersed into epoxy resin using a high-vacuum mechanical stirrer before being incorporated into the UD untreated kenaf and hybrid woven glass/UD kenaf fiber layers. Eight different composite systems were made, namely KFRP, 5 wt % nanosilica in UD kenaf fiber reinforced polymer composites (5NS-KFRP), 13% nanosilica in UD kenaf fiber reinforced polymer composites (13NS-KFRP), 25 wt % nanosilica in UD kenaf fiber reinforced polymer composites (25NS-KFRP), GKFRP, 5 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (5NS-GKFRP), 13 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (13NS-GKFRP) and 25 wt % nanosilica in hybrid woven glass/UD kenaf fiber reinforced polymer composites (25NS-GKFRP). All composite systems were tested in tension and bending in accordance with ASTM standards D3039 and D7264, respectively. Based on the results, it was found that the incorporation of homogeneously dispersed nanosilica significantly improved the tensile and flexural properties of KFRP and hybrid GKFRP composites even at the highest loading of 25 wt % nanosilica. Based on the scanning electron microscopy (SEM) examination of the fractured surfaces, it is suggested that the silane-treated nanosilica exhibits good interactions with epoxy and the kenaf and glass fibers. Therefore, the presence of nanosilica in an epoxy polymer contributes to a stiffer matrix that, effectively, enhances the capability of transferring a load to the fibers. Thus, this supports greater loads and improves the mechanical properties of the kenaf and hybrid composites. [ABSTRACT FROM AUTHOR]

Fiber fracture is a major contributor for the initiation of failure in fiber-reinforced polymer composites. The purpose of this study was to identify where damage occurs when a fiber fractures in a composite. Because this dynamic event occurs in less than 100 1ns, obtaining experimental evidence has been prohibitively difficult. Here, we report a novel method using a model composite, comprised of a spirolactam-based mechanophore-functionalized epoxy resin with a single embedded glass fiber. The ductile epoxy matrix is loaded under tension, which transfers load through interfacial shearing to the embedded brittle fiber, causing the fiber to break into segments. Fluorescence lifetime imaging microscopy (FLIM) is used to visualize regions of mechanophore activation and quantify changes in the dye's local environment such as relaxations on the nanosecond timescale. FLIM of these single fiber fragmentation test (SFFT) samples reveals localized damage zones in the epoxy matrix, not only at the point of fiber fragmentation, but also at distances remote from the fracture site that extend radially into the matrix up to two fiber diameters. The average mechanophore lifetime in the bulk epoxy is (1.5 ± 0.5) ns and in the damage regions is (0.75 ± 0.15) ns. This new data reveals the existence of polymer matrix yielding, which occurs during the fiber fracture event, and agrees with a dynamic model that predicts yielding behavior in the matrix during fracture. These results suggest that the damage from fiber fracture is more extensive than previously recognized. This new approach can be used to elucidate damage in other mechanical tests. The subsequent insights into composite damage mechanisms promises to dramatically accelerate the development of tough, durable, and damage tolerant composites. [ABSTRACT FROM AUTHOR]

This study aims to provide an algorithmic solution to create convertible products, which is then used to fabricate composite components. The shortest optimization path is adapted to this specific conversion problem. The first task was consecutive subcritical water processing and enzymatic hydrolysis optimized by response surface methodology, whereas the second task focused on lignin added composite material to fabricate reinforcement composite and reduce resin rate. The maximum fermentable sugar amount was obtained as 310.9 g/kg under the optimized conditions of 150 bar, 150.9 °C at a flow rate of 8 ml/min for 45 min. Subsequent to subcritical water extraction, remaining solids were processed with enzymes to breakdown cellulose for conversion into simple sugars that can be fermented into biofuels and chemicals, where the highest sugar concentration of 429.45 g/L was reached. Finally, lignin was mixed with epoxy resin at 3 different ratios to fabricate lignin-based glass fiber reinforced composite material. • Subcritical water process was optimized for fractionation of spruce into fermentable sugars and lignin. • Lignin was mixed with epoxy resin to fabricate lignin-based glass fiber reinforced composite material. • The lignin added at low ratios provided increased ductility and strength. • The reversible state was observed by the increase of the lignin ratio in the epoxy. • Lignin-based composite material can be utilized for manufacturing of wind turbine blades. [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]