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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]

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]

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]

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 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]

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]

Fiber metal laminate (FML) is a damage‐tolerant material that has gained special attention in the aircraft industry. To clarify the confusing contributions of constituents to the quasi‐static fracture performance and failure mechanism, six kinds of glass fiber reinforced aluminum laminates (Glare) were designed. Quasi‐static fracture tests were carried out to examine their crack resistance, stable crack extension, and residual strength. Moreover, postmortem characterizations were performed to reveal the macro and micro failure morphologies. It was found that the glass fiber reinforced polymer (GFRP) layers can positively contribute to Glare's quasi‐static fracture performance due to its in‐situ quasi‐brittle but not completely brittle fracture characteristics, which was shown by the special plateau formed on P–Δa curve of Glare, and by the improved crack resistance, longer critical crack length, and higher residual strength in Glare with higher content of GFRP. However, the enhancement achieved by increasing the volume fraction of GFRP was not as effective as by increasing the aluminum thickness, since thickening aluminum in a limited range could increase the fracture toughness and promote the delamination and fiber pull‐outs in Glare. To further identify the effect of the properties of the metal layer, a titanium‐reinforced Glare was designed and tested. It was found to transform the fracture process to be titanium dominant, which delayed the fracture of GFRP and meandered the fracture path, then resulted in superior quasi‐static fracture performance than the basic Glare. [ABSTRACT FROM AUTHOR]

In order to evaluate the severity of thermal degradation on the impact response of carbon (C) and glass (G) fibers reinforced polyether ether ketone laminates, low velocity impact tests have been conducted at a temperature higher than the glass transition temperature (150°C). An instrumented Charpy pendulum (CP) equipped with a heating device was specifically designed to estimate its capability to perform low velocity impact tests at high temperature. The first important effect resulting from temperature increase is a reduction of the impact energy required to induce the barely visible impact damage (BVID), whose role is utmost important regarding the damage tolerance. The second effect is that temperature has also a tremendous influence on the internal damage as there is virtually no delamination at high temperature for impact energies. Finally, compared with the impact behaviors observed with the same laminates impacted with a drop tower and quasi‐static indentation, the impact velocity is about 2.5–3 times as low during CP impacts. As a result, slow loading rates are instrumental in increasing both the dissipated energies and the permanent indentation (PI) values (1.6–2 times as high) that are always higher than the BVID. Ultimately, as higher PI is usually correlated to higher impact damage tolerance. [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]

The present study concentrates on the mechanical, morphological, water absorption and burning behavior of hemp/E‐glass fiber reinforced hybrid composites (FRHC). The surface adhesive characteristics of the acquired bi‐directional hemp fiber mats were enhanced by treating them with an alkali solution. Furthermore, the present work extends to identify the effects of two 2‐dimensional graphene and MXene nanoparticles as filler on the hardness, flexural and tensile behavior as well as water absorption and flammability characteristics of the FRHC. The glass fiber (G), hemp fiber (H), and hemp/glass (G/H) fiber reinforced epoxy LY556 laminates were fabricated by using the hand lay‐up method followed by the vacuum bagging approach. A 30% and 12% increase in the flexural and tensile strength of the H/G hybrid composite has been observed by adding 1% of graphene as an additional reinforcement compared with the neat FRHC. However, the use of MXene as additional reinforcements shows 45% and 10% enhancement in the flexural and tensile strength of the H/G hybrid composite. In addition, the water absorption capacity of MXene‐filled G/H hybrid composites is found to be almost half of that filled with graphene. Similarly, the flammability results reveal that the burning rate of graphene‐reinforced H/G hybrid composite is 17.44 mm/min. When comparing the mechanical, water absorption, and flammability characteristics of graphene and MXene‐reinforced G/H hybrid composites, graphene gives more intensifying results than MXene. The scanning electron microscopic studies are also incorporated to investigate the fractured surface topography of the FRHC. [ABSTRACT FROM AUTHOR]

In this study, two different type of glass and carbon fiber hybrid laminates were manufactured using a low‐viscosity thermoplastic resin that is, Elium®. A detailed microstructure visualization study was conducted using X‐ray computed tomography (XCT) analysis. The viscoelastic properties were examined through dynamic mechanical analysis. The mechanical performance was investigated through flexural and tensile tests along with a fractographic study using optical and scanning electron microscopy. The XCT analysis revealed a weak interface between the Elium® resin and the glass fabric, with glass fiber specimens exhibiting a void content of 1.24%, in contrast to the carbon fiber specimens which showed void content of only 0.28%. Therefore, adding glass fabric layers in the hybrid laminates increased the void content, which had a negative impact on the overall mechanical performance. The average flexural strength of the hybrid specimen having G2C4G2 stacking sequence was observed to be 254% higher than pure GFRPC specimens. Similarly, the tensile strength and Young's modulus of the same hybrid specimen showed 155% and 380% increases, respectively, compared to the GFRPC specimens. This increase was primarily due to higher stiffness of the carbon fibers and their better fiber – matrix interface. Whereas the tensile strain of the hybrid specimen having G3C2G3 stacking sequence was 37% higher than that of the CFRPC specimens. The SEM images highlighted fiber fracture and brittle failure modes in the carbon fiber specimens, in contrast to fiber pullout, interfacial failure, poor fiber‐matrix bonding and ductile failure modes in the glass fiber specimens. [ABSTRACT FROM AUTHOR]

Fiber‐metal laminates (FMLs) are attracting much attention from researchers as emerging aerospace materials. In this paper, 1060‐H112 aluminum alloy‐carbon/glass fiber laminates were prepared by vacuum bagging method. Subsequently, based on tensile, three‐point bending and low‐velocity impact experiments, the quasi‐static mechanical properties as well as the dynamic response to impact of the two fiber laminates were investigated. The results show that the carbon fiber metal laminate (CARALL) has stronger tensile strength and inter‐ply tensile consistency, while the glass fiber metal laminate (GLARE) has better bending resistance. The impact response of CARALL and GLARE is closely related to the impactor shape and impact energy. The peak loads of the FMLs increased with increasing impact energy over the range of impact energies tested. However, the peak load of CARALL is more sensitive to the impact energy, while the deformation of GLARE is more sensitive to the impact energy. With complete penetration of the impactor into the target, the fibers of GLARE were ductile fracture and fibers of CARALL were brittle fracture for the blunt impactor impact, while the fibers of both GLARE and CARALL were ductile fracture for the hemispherical impactor impact. Under the impact of both impactors, two types of FMLs showed matrix broken, delamination, and local debonding. [ABSTRACT FROM AUTHOR]

For enhancing impact characteristics, woven glass fiber epoxy laminates are reinforced with short fibers. The 6‐mm‐long slender fillers, when added up to 4% in the matrix, exhibit no influence on the flexural modulus, but at 2% they maximize the laminate's flexural strength. While the dissipation energy continues to increase up to 30 J of impact, the laminates' post‐impact load bearing capacity gets significantly affected beyond 20 J. The reinforced laminates exhibit better elastic response and enhanced damage resistance with as high as 50% reduction in the visible damage area as well as up to 35% increase in the damage initiation force. The degree of damage shows excellent correlation with the visible damage area. The distinct through thickness conical region, diverging from the impact site, is attributed to the presence of microcracks oriented along the fiber directions. The cone boundary, from where the interlaminar failure initiates, is largely the manifestation of transverse matrix cracks. While the damage cone with greater divergence indicates reduced impact resistance of the laminate, the orientation of transverse matrix cracks remains unaffected by the impact energy or the filler content. At low impact energies, the failure initiated from the fiber/matrix interfaces, coalesce to form the matrix cracks, which act as a precursor to the interlaminar failure. However, at high energy levels, several failure mechanisms simultaneously develop with no clear indication of the order of damage evolution. The short fibers enhance the laminate's impact resistance either by arresting the cracks or by developing tortuous crack path with high energy dissipation. [ABSTRACT FROM AUTHOR]

Drilling process of fiber metal laminates (FML) requires a proper design of the processing parameters to prevent the occurrence of several issues and minimize defects, which can be detrimental for the integrity of the parts. These aspects become more critical in dry machining used in aeronautic field. In this scenario, the monitoring of process temperature is crucial to obtain useful information for machining optimization since many critical factors, such as matrix burnout, fiber pull‐out and delamination, depend on the heat generated during the machining. The aim of this work is to monitor the temperature measured on the tool and workpiece during dry drilling of Al/GFRP (GLARE) and Al/CFRP (CARALL) hybrid laminates. The influence of the cutting speed on the temperature trends was analyzed. Two different set‐ups were designed to measure the temperature on the tool, near the cutting edge and on the flank, and inside the laminate, in both the metallic and the composite parts. In addition, a numerical model to analyze the process temperature trend during drilling has been developed. The increasing the spindle speed from 1500 to 8000 rpm resulted in a decreasing of maximum temperatures of approximately 10°C on the tool tip and on the flank for the GLARE, and of almost 20°C in the CARALL laminates. The numerical simulation also pointed that the temperature fields is dictated by the thermal properties of carbon and glass fibers: temperature profiles within the CARALL were found smoother than those observed in GLARE. [ABSTRACT FROM AUTHOR]

Due to environmental issues and high cost of synthetic fibers, natural or cellulosic fibers have emerged as a promising reinforcement for polymer composites. The hybridization of natural fiber with synthetic fiber is a useful technique to improve the mechanical properties instead of using the natural fibers alone. This research aims to evaluate the influence of glass fiber hybridization on the mechanical properties of continuous, unidirectional, alkali (NaOH)‐treated kenaf‐epoxy composites. At first, the effect of treatment of various concentrations (3, 5, 7, and 9% w/v) of NaOH on the structure of single kenaf fiber was characterized using XRD, SEM, FTIR, and tensile testing. At the optimum 5% alkali concentration the tensile strength, modulus, and %elongation of the kenaf fibers were enhanced by 81%, 114%, and 42%, respectively. The effect of hybridization of 5% NaOH treated kenaf along with glass fiber on the improvement in tensile, flexural, and impact properties for hand laid kenaf‐glass‐epoxy hybrid composite laminates was established. The overall matrix to fiber weight ratio of five different layup sequence laminates was maintained constant at 70:30. It can be concluded from the obtained results that the 15% glass and 15% kenaf fiber hybridized composites exhibited the maximum increment in tensile strength and modulus (68.5% and 19.5%, respectively) in comparison to the unhybridized composites. Further, the flexural strength and modulus were also improved by 21% and 67%, respectively, and the impact strength by 153%. The SEM fractography proved that alkali treatment of fibers improved the fiber‐matrix interfacial bonding whereas fiber breakage, fiber pull‐out and debonding were established as the main fracture mechanisms of hybrid composites. The findings of the present investigation on kenaf‐glass hybrid composites corroborate that they are suitable for secondary structural applications in construction and automobile sectors. [ABSTRACT FROM AUTHOR]

In this present study, a high‐performance structural epoxy biocomposite has been prepared and characterized for its mechanical, wear, and fatigue behavior. The main aim of this research was to determine the effect of fiber stacking order and the biosilica addition in the epoxy hybrid composite when it is subjected to external loading. The research also focused on how the surface treatment process on fiber and particle affects the mechanical, wear, and fatigue behavior of composite. The biosilica particles were synthesized from black rice husks and then surface treated with 3‐aminopropyltriethoxysilane. Similarly, a base treatment was applied to fiber mats and the composite laminates for this investigation were fabricated by hand layup process. It is noted that the composite designations E12 and E22 exhibited an improved tensile strength of 58, 62% and flexural strength of 45, 51% for 1.0 vol% biosilica in both staking sequence models. Similarly, in inter‐laminar shear strength the composites E2, E21 and E22 outperformed than E1, E11, and E12. In terms of Izod impact toughness and hardness, composite designation E22 provides maximum increment of about 94% and 5%. The wear resistance of composite E22 exhibited lower wear loss and COF. The highest fatigue life count of 41,782 was observed for the composite designation E22 in tension‐tension fatigue mode. Overall the stacking order R/A/G/A/R gives better results than others. These load bearing properties enhanced hybrid composites might be employed in structural, industrial, automotive, home appliance, defense, and lightweight industrial applications. [ABSTRACT FROM AUTHOR]

This research deals with the effect of stacking sequence over, the mechanical behavior of laminates that includes tensile, flexural, fractography, area of impact damage, and residual tensile strength. The angle‐ply laminate specimens were analyzed theoretically and correlated with experimental results. The highest interlaminar shear strength 32.89 MPa was exhibited by (60/30/60/30)S with better transverse stiffness of 444 N/mm. Among the developed laminates, (60/30/60/30)S showed the highest rate of residual strength degradation of 0.271. It has been found that an increase in interlaminar shear strength decreases the impact damage resistance of the composites. The angle‐ply laminate composites exhibited superior residual tensile and impact resistant properties when compared with uniply laminate composites. [ABSTRACT FROM AUTHOR]

Steel fiber is the most common metal fiber used due to its cost‐effectiveness, high performance, and availability despite its heavyweight. This study is an attempt to evaluate the mechanical properties of steel/glass fiber and steel/basalt fiber‐reinforced epoxy composites. The symmetric hybrid laminates were produced by replacing the innermost 1, 2, 3, and 4 layers of steel fiber (200 mesh size) with basalt and glass fiber layers. The specimens were subjected to tensile, flexural, and Charpy impact tests in accordance with relevant ASTM standards. Moreover, fracture surfaces were analyzed, and the micrographs were obtained using a scanning electron microscope. The results showed that a high improvement in tensile strength was achieved with BS1–E (1 layer steel mesh–8 layers basalt) and GS1–E (1 layer steel mesh–8 layers glass) hybrid composites, with an increase of 528% and 233%, respectively, compared to steel fiber reinforced epoxy composites. Similarly, BS1–E and GS1–E hybrid composites showed the highest flexural strength increase of 82.2% and 66.8%, respectively, compared to steel fiber reinforced epoxy composites. Consequently, the potential to hybridize steel fiber with glass fiber and basalt fiber could create new materials with unique physical structures and synergistic effects on mechanical properties. [ABSTRACT FROM AUTHOR]

In the present study, an attempt is made to replace the synthetic glass fiber used in the FRP structures in terms of natural flax fibers without much sacrifice on static and dynamic stability of the structure. Three types of glass/flax hybrid composite laminates were prepared with different fiber volume fraction of glass and flax fibers. For better understanding purpose, a dedicated glass and dedicated flax laminates were also fabricated. All the laminates were fabricated by vacuum bag molding method with uniform laminate thickness. The mechanical properties of the fabricated laminates, such as tensile strength and flexural strength, were evaluated in accordance with ASTM standards. The impulse excitation technique was used to assess the free vibration characteristics of glass/flax laminates such as modal frequency and material damping. Based on experimentally evaluated mechanical and vibration characteristics a suitable fiber volume fraction for the preferred laminate thickness was suggested to achieve optimum static and dynamic stability. [ABSTRACT FROM AUTHOR]

In this article, continuous glass fiber reinforced thermoplastic prepreg is proposed using maleic anhydride grafted polypropylene (MAPP) as the matrix resin. The compression molding parameters and plying sequences are optimized. Under the process parameters of 155°C and 15 MPa, both the tensile and flexural properties achieve the maximum values, and the plying sequence of (0°/90°) possess a balanced mechanical performance. Then, MAPP/GF/Al fiber‐metal laminates are further fabricated in two stacking configurations of 2/1 and 3/2. The mechanical results showed that the tensile and bending strength were basically maintained, while the modulus are significantly enhanced by 114.9% and 135.4% in 2/1 and 3/2 fiber metal laminates (FMLs) in contrast with MAPP/GF controls. In addition, the large deflection behavior in bending test for FMLs suggest that MAPP/GF and aluminum alloy show a synergy deformation due to the good bonding between metal layer and thermoplastic resin. The optical microstructure also revealed that the interlaminar adhesion are well joined between FML constituents. The findings in this study are important from a design viewpoint of FMLs because of the lower material cost, less processing time, and good lightweight effect, which potentially be tailored to use as structural parts in automobile applications. [ABSTRACT FROM AUTHOR]

Monitoring the curing defects as well as damages that occur in the fabrication and application process is important for ensuring the safety of composite structures. In this paper, a highly sensitive 1‐D line sensor is designed to achieve self‐sensing and diagnosing functionalities in both the fabrication and application of glass fiber reinforced epoxy (GF/epoxy) composites. The sensor consists of multi‐walled carbon nanotube coated glass fiber (MWCNT@GF), which is sensing the damage by the principle of resistance change. Due to the vacuum‐assisted resin infusion process, the MWCNT@GF sensor is embedded into GF/epoxy composite laminates, and hence, it can monitor the resin frontal flow, curing, and especially the flow defects. In the subsequent application, the tensile performance of a GF/epoxy composite joint is evaluated by not only the force‐displacement curve but also the displacement‐dependent resistance change of the sensor. Tensile damage modes are distinguished, which is for the first time to be reported. The MWCNT@GF sensor is mechanically stable and highly sensitive; hence, it can be used to follow the composite performance from fabrication until the end of life. [ABSTRACT FROM AUTHOR]

This paper reports the effect of weight concentration of graphene nanoplatelets (GNPs) on the electrical, mechanical, thermo‐mechanical, and piezoresistive properties of unidirectional glass fiber/epoxy composite laminates. The neat (without GNPs) and multiscale laminates (with GNPs) were fabricated with different GNPs contents (0.25, 0.50, 0.75, and 1.00 wt%) using a simple and feasible process based on spray coating followed by vacuum assisted resin infusion. The morphological analysis on glass fiber surfaces evidenced the presence of an effective GNP network formation which tends to be denser as GNPs content increases. As a result, the electrical conductivity and gauge factor measured on top and bottom surfaces of specimens were greatly increased in laminates. Short beam shear and flexural test results showed that the addition of GNPs to the laminates causes a significant reduction in their interlaminar shear strength, flexural strength, and strain to failure with respect to the neat laminate. However, the flexural modulus of laminates does not suffer any apparent change in its reference value and the glass transition temperature was slightly increased in samples with 1.00 wt% GNPs. The fractographic analysis revealed that delamination was the main damage mechanism detected upon mechanical testing, suggesting that relative high concentrations of GNPs cause that interlaminar regions of laminated composites become weaker. In spite of this, excellent strain self‐sensing capabilities and internal damage detection were observed during flexural electromechanical tests performed in beam‐type specimens with higher GNP content. [ABSTRACT FROM AUTHOR]

Hybrid composites have become the focal point of research communities due to the balance in mechanical and ecological properties of such materials. Hybridization is an efficient technique to strengthen and enhance the performance of composite materials. In this research study, hybrid composites were prepared by embedding pineapple leaf and glass fibers in polypropylene polymers via the hot press molding compression technique. Mechanical tests were carried out to determine the tensile, flexural and Charpy impact properties of pineapple leaf/glass fiber‐reinforced hybrid composite laminates. Additionally, water absorption test was also conducted to investigate the influence of hybridization on the moisture uptake of hybrid composites. In accordance with the findings obtained, the hybridization of pineapple leaf with glass fibers was found to improve the mechanical properties and moisture uptake sensitivity of the composite laminates. The [G/P/G] composite laminates are especially promising, having comparable mechanical strengths to those of non‐hybrid [G/G/G] composite laminates. Meanwhile, the water absorption and diffusion coefficient of [G/P/G] composite laminates were 66.64% and 40.71% lower than non‐hybrid [P/P/P] composite laminates. Based on the findings obtained, it is anticipated that the hybridization of pineapple leaf and glass fibers endows the composite laminates with lightweight characteristic, remarkable mechanical properties and low moisture uptake sensitivity while improving the environmental friendliness of the materials. Therefore, hybrid composites have indeed attested a very high potential to be used in transportation sectors. [ABSTRACT FROM AUTHOR]

Sheet molding compounds (SMC) are commonly used in automotive applications as they lead to increased fuel efficiency of vehicles due to their high strength to weight ratios. This study focuses on understanding the effect of replacing calcium carbonate (CaCO3) with hollow glass spheres (HGS) in an unsaturated polyester resin matrix SMC composite with the ultimate goal to further reduce density without compromising performance. The resulting glass fiber (GF)‐reinforced syntactic foam laminate composites with GF content ranging from 10 to 15 vol% have densities of 1.2 and 1 g/cm3, respectively. This is significantly lower than the industry standard SMC density of 1.9 g/cm3. The HGS parameters of interest are primarily HGS type (S28HS and S32HS), loading level (33–44 vol%), and surface functionalization (methacrylsilane). The syntactic foam composites were characterized in terms of tensile, flexural, and impact properties, and their properties were compared to those of standard density SMC. As expected, the flexural, tensile, and impact properties were compromised with a decrease of density. However, they were higher than the corresponding properties of low‐ and ultra‐low density composites reported in the literature, as we were able to add higher GF content in these low‐density SMC formulations. It was also concluded that methacrylsilanized surface treated HGS showed promise in maintaining the mechanical properties, especially at high sphere loadings. The impact energy of the low‐density formulations was relatively unaffected by HGS type or loading. [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]

In this research work, the low‐velocity impact behavior and post impact performance of carbon/epoxy laminates modified with milled glass fibers was investigated. Unidirectional (UD) and Cross‐ply (CP) carbon/epoxy laminates were incorporated with milled glass fibers by 5 wt% of epoxy. Low‐velocity impact test was performed at impact velocity of 3, 3.5, 4, 4.5, and 5 m/s, respectively and the results were correlated with the baseline samples without filler. The filler loaded samples exhibited higher peak force, lesser deformation, and lower damage degree than the baseline samples. The milled glass fibers in the interlaminar zone restricts the delamination crack propagation resulting in reduced impact damage area and also promotes additional energy dissipation mechanism including filler debonding/pullout. Furthermore, the CP filler‐loaded samples show higher residual load‐bearing capacity for impact velocities 3, 3.5, and 4 m/s, respectively. Although the unidirectional filler‐loaded samples showed better load bearing capacity for impact velocities beyond 4 m/s. POLYM. COMPOS., 40:2441–2451, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Aim of this article is the assessment of the bearing mechanical performances of pin‐loaded glass laminates as function of their geometrical configuration. To this concern, 32 specimens having different hole diameter (D), laminate width (W), and hole center to laminate free edge distance (E) have been tested under bearing conditions. The maximum bearing stress and the stress‐displacement curves were analyzed as function both of hole to laminate free edge distance E and hole diameter D. Moreover, an experimental 2D failure map was created by placing the experimental results (i.e., the kind of failure mechanism occurred for each geometrical configuration) in the plane E/D versus W/D ratios. In order to identify a simplified methodology able to design mechanically fastened joints in an easy and effective way, a simplified theoretical failure map on E/D and W/D axes was proposed. The theoretical model showed a good matching with the experimental results validating the proposed approach. In particular, the proposed simplified failure map highlighted that woven glass fiber composite laminates fastened joints should have E/D and W/D ratios higher than 1.6 and 2.1, respectively, in order to stimulate a progressive bearing failure mechanism and achieve the full laminate strength. Finally, another goal of this article was to assess failure mechanisms evolution by drawing a 3D plot (i.e., at varying E/D and W/D geometrical ratios) of the failure index evaluated for each failure mechanism according to the maximum stress criterion. POLYM. COMPOS., 40:1087–1096, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Present study addresses the influence of stacking sequence effect on damage tolerance and impact behavior of hybrid composite laminates. Hybrid composite samples were fabricated with two and three different fiber combinations of woven carbon, Kevlar, and glass fibers. The behavior of impact resistance was measured by using as instrumented drop weight impact machine. The resulting failure and damage tolerances were compared with observing the impacted and nonimpacted surfaces. The degree of the hybridization effects was evaluated with reference to rule of mixture in terms of absorbed energy. The results from this study showed that the position of fibers in the hybrid samples was a major factor regarding to damage mechanism and impact resistance. Due to the asymmetric structure of the hybrid samples, the side of their impacted surfaces was significantly affected the load and deflection characteristics during the impact event. POLYM. COMPOS., 39:3129–3139, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Glass woven fabric/polypropylene laminates have been studied given their outstanding performance/cost ratio. Their flexural properties, mainly influenced by the adhesion between matrix and reinforcing fibers, have been investigated for systems containing maleated polypropylene (PP- g-MA) amounts ranging from 0% to 10% by weight. Results have shown that the presence of the compatibilizer improves both flexural modulus and strength, achieving plateau values approximately for 5 and 2 wt% of PP- g-MA, respectively. On the contrary, an inverse proportion between the compatibilizer content and the energy dissipated at perforation emerged from low velocity impact tests. The different dependence can be related to the failure mechanisms occurring at the fiber/matrix interface. These mechanisms are able to dissipate large amounts of energy through friction phenomena, and are pronounced when the fiber/matrix adhesion is weak. Pull-out of fibers from the matrix has been detected, in particular, in systems containing low contents of compatibilizer and evidenced by the morphological analysis of fracture surfaces after failure. The large amount of energy dissipation allowed by the relative motion of fibers and matrix occurred before fiber breakage, as confirmed by the evaluation of the laminates ductility index. POLYM. COMPOS., 37:2452-2459, 2016. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The empirical model recently found by the authors for the prediction of the indentation depth was verified for composite laminates different in matrix and fiber subjected to low velocity impact loads. The data obtained in a previous research on common glass and carbon fiber laminates made by commonly used epoxy matrix, were here compared to the results obtained on laminates made by glass fibers immersed in phenolic matrix and novel basalt fibers immersed in epoxy resin. The model takes into explicitly account the tup diameter and presents the advantage that only a single material constant to be experimentally determined is necessary for the prediction. The comparison showed that the value of the constant is different for the different material systems analyzed so that it can be assumed as an index for the indentation sensitivity. POLYM. COMPOS., 36:987-991, 2015. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Bisphthalonitrile (BAPh)/polyarylene ether nitrile end-capped with hydroxyl groups (PEN-OH) composite laminates reinforced with glass fiber (GF) have been fabricated in this article. The curing behaviors of BAPh/PEN-OH prepolymers have been characterized by differential scanning calorimetry and dynamic rheological analysis. The results indicate that with the introduction of PEN-OH the curing temperature of BAPh has decreased to 229.6-234.8°C and BAPh/PEN-OH prepolymers exhibit large processing windows with relatively low melt viscosity. The BAPh/PEN-OH/GF composite laminates exhibit tensile strength (272.4-456.5 MPa) and modulus (4.9-10.0 GPa), flexural strength (507.1-560.9 MPa), and flexural modulus (24.0-30.4 GPa) with high thermal (stable up to 538.3°C) and thermal stabilities (stable up to 475.5°C). The dielectric properties of BAPh/PEN-OH/GF composite laminates have also been investigated, which had little dependence on the frequency. Meanwhile, scanning electron microscopy results show that the BAPh/PEN-OH/GF composite laminates display excellent interfacial adhesions between the matrix and GFs. Herein, the BAPh/PEN-OH matrix can be a good matrix for high-performance polymeric materials and the advanced BAPh/PEN-OH/GF composite laminates can be used under high temperature environment. POLYM. COMPOS., 34:2160-2168, 2013. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A correction to the article "The Comparison of Low-velocity Impact Resistance of Aluminum/Carbon and Glass Fiber Metal Laminates," that was published in a previous issue is presented.