Interlaminar Shear Strength Research Articles

Mechanical improvement of carbon fiber/epoxy composites by sizing functionalized carbon nanotubes on fibers

AbstractA sizing agent mainly consisting of polyethersulfone and acidified multi‐walled carbon nanotubes (MWCNT) was developed for surface modification of carbon fibers (CF) to enhance the interfacial bond and to form carbon fiber‐carbon nanotube (CF‐MWCNT) multiscale reinforcements. To prepare the modified carbon fiber/epoxy resin composites (CFRP), a vacuum molding technique was used in this study. The effects of the MWCNT‐containing sizing agent on the morphology and chemical structure of the CF surface were observed by scanning electron microscopy and Fourier transform infrared spectroscopy. The influence of MWCNT length and content on the mechanical properties of CFRP were also studied. The experimental results showed that the strength of the CFRP decreased with the increase of MWCNT length, and the MWCNT with a content of 0.05 wt% had a good reinforced effect on the CFRP. After the sizing treatment, the interlaminar shear strength (ILSS) of the CFRP is increased. These enhancements are attributed to the improved mechanical bonding and chemical bonding between CF and resin matrix. The MWCNT provides nanosized rough surface to CF and these acidified MWCNTs attached to the surface of CF with polar oxygen‐containing functional groups improve the compatibility with reinforcement and resin matrix.Highlights Carbon fiber was modified by a sizing agent mainly consisting of polyethersulfone and acidified carbon nanotube (CNT). CNTs enhance the interfacial chemical bonding and mechanical bonding. The CNT length affects the mechanical properties of the carbon fiber/epoxy resin composites (CFRP). The modified carbon fiber has enhanced the mechanical properties of the CFRP.

Synergistic cooperation of a Magnolol-based waterborne cross-linkable PEEK sizing agent and click chemistry to construct exceptional solvent-resistance and interfacial properties of CF/PEEK composites

Despite the impressive strides on waterborne cross-linkable sizing agents for carbon fiber (CF)-reinforced polyether ether ketone (PEEK) composites, the vast majority of polymer precursors employed for sizing agents in existing researches are derived from petroleum resources. On the other hand, the notable influence of the adhesive strength between sizing agent and CF on the interfacial properties of composites has been consistently disregarded. Herein, a waterborne cross-linkable sizing agent was prepared capitalizing on naturally existing magnolol. Meanwhile, sulfhydryl groups were chemical-grafted on the surface of CF via click reaction, setting stages for subsequent interaction with magnolol units via a second click reaction to effectively enrich the force between CF and sizing layer. As a unique feature of the system, the inherent mechanism of the sizing coating layer comprises self-crosslinking of the orchestrated propenyl groups toward sturdy structures during hot-pressing, contributing to unrivalled solvent-resistance and unorthodox interfacial robustness. As a result, the bending strength, interlaminar and interfacial shear strength of the derived composites were promoted by 35.48 %, 47.87 % and 61.03 %, respectively. Noteworthy, the mechanical properties of Sized-CF composites were well-preserved after solvent aging treatment. Therefore, this protocol developed a novel bio-based waterborne cross-linkable sizing agents of PEEK derivative, laying a good foundation for advanced CF/PEEK composites with excellent interfacial performance.

High Temperature Experiments and Properties of Carbon Polyimide Composites

The interlayer shear tests of AC741/M55JB carbon fiber reinforced composite at room temperature, 400℃, 600℃ and 800℃ were carried out.The longitudinal and transverse shear tests of AC741/CCF800 carbon fiber reinforced composite were carried out at room temperature, 400℃, 600℃ and 800℃ dry conditions, as well as the experiments to calculate material property parameters. The results showed that the main failure mode of the sample in the interlayer shear test was stratified damage, and the fracture of the upper surface material was not obvious.This is due to the different types of tests, the interlayer shear pattern is short and small, and it is not easy to occur the fracture damage of the material without stratification.In addition, with the increase of temperature, the interlaminar shear strength also decreased significantly.In crossbar shear test, the maximum in-plane shear stress, maximum in-plane shear strength and in-plane shear modulus of the material gradually decrease with the increase of temperature, thus changing the bearing property of the material.

Impact of ply stacking sequence on the mechanical response of hybrid Jute-Banana fiber phenoplast composites

Natural fiber composites are increasingly gaining popularity as a cost-effective and environmentally friendly alternative to synthetic fibers. Incorporating a variety of fibers enhances mechanical properties. The arrangement of fibers plays a crucial role in determining the mechanical characteristics of laminate composites. Therefore, the primary objective of this study is to investigate how the stacking order of jute (J) and banana (B) fibers affects the mechanical behaviour of composites made from phenolic resins. Four different fiber mat stacking sequences (J/B/B/J, B/J/J/B, J/B/J/B, and J/J/B/B) were used for developing the eco-fiber composites using the heat-press technique. Several mechanical parameters were assessed, including tensile strength, flexural strength, impact strength, and inter-laminar shear strength (ILSS). The experimental results indicated that the JBBJ composite exhibits superior tensile strength (46.65 MPa) and modulus (993 MPa) compared to the other composites due to the presence of high-strength jute fibers on the surface. Additionally, the flexural strength of the JBBJ composite (87.24 MPa) was found to be noteworthy. It was observed that the impact strength of jute fibers surpasses that of banana fibers. Consequently, the JBBJ composite demonstrates higher values for energy absorption (0.482 J) and impact strength (120 J m−1) compared to the other composites tested. Moreover, the JBBJ composite displays higher inter-laminar shear strength and hardness values compared to BJJB, JBJB, and JJBB by 30%, 35%, and 43%, respectively. Scanning electron microscope microphotographs reveal strong correlational fracture failure mechanisms, indicative of improved mechanical properties in the JBBJ composite. Based on the experimental results, it is evident that the JBBJ composite can be utilized in lightweight applications.

Interlaminar reinforced carbon fiber/epoxy composites by electrospun ultrafine hybrid fibers

The demand for high-strength composites in the aerospace industry is increasing; however, their low-impact resistance poses a danger to aircraft. Consequently, significant attention has been devoted to researching the interlaminar toughening of carbon fiber-epoxy composite laminates, focusing on electrospun fibers due to their high porosity and specific surface area. Our previous work explored the potential of poly(aryl ether nitrile) as an interlaminar toughening option. Nonetheless, these materials exhibited a decline in flexural properties. To address this concern, we developed poly(arylene ether nitrile)-poly(ε-caprolactone) ultrafine hybrid fiber membranes via electrospinning to enhance the interlaminar performance of composite laminates. The interlaminar fracture toughness demonstrated a remarkable improvement of 132.5 %. Additionally, the flexural strength in-creased by at least 12.3 %, while the flexural modulus experienced a minimum in-crease of 17.9 %. The interlaminar shear strength improved by approximately 27%–28 %, and the impact strength increased by 99.2 %. This study demonstrates the significant potential of electrospun hybrid fiber membranes in improving the interlaminar properties of carbon fiber-epoxy composite laminates, con-tributing to developing safer and more durable materials for the aerospace industry.

Exploring the impact of hybridization on green composites: pineapple leaf and sisal fiber reinforcement using poly(furfuryl alcohol) bioresin

Abstract This study aimed to examine the mechanical and physical characteristics of hybrid composite prepared using bio-epoxy reinforced with natural fibers extracted from pineapple leaf (PLF) and sisal (SF). The hand lay-up technique was utilized to fabricate the hybridized composite from bi-directional pineapple leaf fiber and sisal fibers using various stacking sequences. In order to understand the impact of hybridization on these composites, physical properties including density, percentage volume of fiber (PVF), and water absorption capacity were ascertained for hybrid composite. In addition, the mechanical characteristics like the tensile, fracture toughness, flexural, and interlaminar shear (ILSS) tests were investigated. Poly(furfuryl alcohol) was prepared and used as bioresin and it was apparent that the addition of more PLF in terms of PVF into hybridized composites, the properties flexural, tensile, and ILSS of the bio-epoxy composites were notably improved. The mechanical properties of hybridized composites were markedly impacted by the stacking order. Inference revealed that the composite attained the maximal tensile strength of 70.8 MPa for alternative sequence of SF and PLF. The composite which contained SF on the outside, had outperformed compared to other hybrid composites in terms of fracture toughness (3302.3 J/m2) and interlaminar shear strength (16.1 MPa).

Novel thermoplastic matrix resin with low processing temperature and good interfacial strength for carbon fiber-reinforced polyethersulfone

Owing to the increased demand for carbon fiber-reinforced thermoplastic composites with excellent recyclability, there is a need to improve the interfacial bonding between the fiber and matrix. Hydroxy-functionalized polyethersulfone (PES), i.e., PES-OH, and epoxy resin (ER) were included to impart functionality to PES. A mixture of PES, PES-OH, and ERs with a weight ratio of 8:1:1 reduced the Tg by −18% compared with 100% PES. The enhancement of the interfacial properties increased the interlaminar shear, tensile, compressive, and residual compressive strengths by 50%, 22%, 43%, and 25%, respectively. This study can contribute to the development of carbon fiber composites for future mobility.

Mechanical Properties of Aramid Fiber Fabrics and Composites Enhanced by Phthalic Anhydride Catalyzed with Anhydrous Aluminum Chloride

The surface modification of aramid fiber plain fabric (PPTA) was conducted through phthalic anhydride treatment and anhydrous aluminum chloride (AlCl3) catalysis, aiming to enhance the interfacial bonding strength between aramid fiber fabric and bisphenol A diglycidyl ether (DGEBA) resin. The surface morphologies and structures of PPTA fiber before and after modification were characterized using scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and X-ray diffractometry. The mechanical properties of the PPTA/DGEBA composite were evaluated using a universal mechanical testing machine. The results demonstrate that when the concentration of phthalic anhydride is 0.3 mol/L, the tensile strength, bending strength and interlaminar shear strength of PPTA/DGEBA composites reach the maximum value, which are increased by 17.94%, 44.18%, and 15.94% compared with the unmodified sample, respectively. After a 0.5-h catalytic modification, the PPTA/DGEBA composites exhibited significantly enhanced tensile strength, bending strength, and interlaminar shear strength, achieving respective increments of 32.28%, 24.91%, and 29.10% compared to the modified samples without catalyst addition. Moreover, the overall mechanical properties of the aramid fiber fabrics and composites were substantially improved, which are more suitable for structural applications.

Investigation of mechanical properties and self‐healing efficiency of carbon fibers composites infused with unsaturated polyester vitrimer

AbstractUnsaturated polyester resins (UPR) are widely in composite manufacturing, particularly in the energy, wind, and construction sectors. When these composites sustain damage, defects or cracks, several methodologies are employed to heal and repair them to extend their lifespan while reducing environmental impacts. In this work, the use of vitrimeric UPR (UPRv) as a matrix for carbon fiber composite, was investigated in terms of healing efficiency by mechanical and thermal properties. Flexural and interlaminar shear strength tests revealed healing efficiencies exceeding 40% and 90%, respectively. These results were attributed to the transesterification exchange occurring within the crosslinked networks of UPRv. As described in our previous work, the incorporation of “Covalent Adaptable Networks (CANs)” enables the conversion of commercial thermoset (UPR) into vitrimeric resins, thereby providing reprocessing and healing capabilities. Furthermore, a comparison between pristine and healed composites with Mode I DCB and Mode II ENF tests, confirm how the introduction of vitrimer in composite facilitates the manufacturing of a self‐healing product, with a significant recovery of the original properties.Highlights Application of a previous synthetized vitrimeric unsaturated polyester resin (UPRv)—fabrication of CF's composites reinforced with UPRv—investigation of the self‐healing property of the developed laminates—potential application as green and sustainable composites.

Carbon-nanotube-grafted glass-fiber-reinforced composites: Synthesis and mechanical properties

Glass fibers (GFs) are commonly used as reinforcements for advanced polymer composites. To improve the interfacial shear properties and mechanical properties of GF-reinforced composites (GFRPs), carbon nanotubes (CNTs) are directly grafted onto GFs using chemical vapor deposition (CVD). However, this process requires high temperatures, which causes thermal degradation of GFs, deteriorating their mechanical properties. In this study, a low-temperature CNT-grafting process was investigated using a bimetallic catalyst introduced onto a GF fiber surface via precursor solutions. The mechanical properties of the CNT-grafted GFs fabricated at different CVD temperatures were evaluated; they consistently showed low tensile strengths at temperatures above 400 °C. Subsequently, various CNT-grafted GFRPs were manufactured, and their mechanical properties were characterized. Interestingly, the flexural strengths of the composites increased with maintained tensile strength, despite a deterioration of the CNT-grafted GF reinforcements due to the CVD process. This could be attributed to the improved interfacial shear strength (IFSS) of the CNT-grafted GFs at the fiber level, and the enhanced compressive strength and interlaminar shear strength (ILSS) of CNT-grafted GFRPs at the composite level. Considering the properties of GF through CVD processes, particularly in relation to temperature, and factors such as IFSS, ILSS, tensile, compressive and flexural properties of composite materials, grafting CNTs on GF via a CVD system demonstrated its highest optimality at 450 °C.

Effects of surface modification on mechanical properties and electromagnetic interference shielding properties of carbon fiber/silk fiber hybrid composites

AbstractIn this paper, a hybrid approach was employed by integrating a high‐modulus, high‐tensile‐strength carbon fiber fabric (CFF) with a low‐density, high‐toughness silk nonwoven fabric (SNWF) to fabricate CFF‐SNWF reinforced epoxy (CFF‐SNWF/EP) hybrid composites. Through the surface freeze‐induced self‐assembly process, the multiscale hybrid modified layers were successfully constructed on the surfaces of both CFF and SNWF. This novel approach effectively enhanced the interfacial strength of the hybrid fibers (HFs). Comparing the performance of the modified composites with unmodified CFF reinforced epoxy (CFF/EP), significant improvements in both tensile strength and interlaminar shear strength were observed. Specifically, the tensile strength and interlaminar shear strength of the modified composites reached 626.7 and 39.16 MPa, a rise scope of 17.1% and 14.8%, respectively. In addition, the hybrid fibers reinforced polymers (HFRPs) exhibited a superior electromagnetic interference (EMI) shielding capabilities. For insistence, the modified CFF/EP with a thickness of 2.0 mm showed an impressive EMI shielding effectiveness value of 50 dB. These findings underscore the promising application potential of CFF‐SNWF/EP hybrid composites, particularly in the field of consumer electronics.Highlights The surface of hybrid fiber was modified by PDA‐GO‐OCNTs‐WPU. Multi‐scale structure contributes a lot in composite performance. Hybrid effect before and after interfacial modification is performed. The hybrid interface modification and hybrid structure were analyzed.

Strengthening the bonding interfaces of carbon reinforced aluminum laminate by slot structure

AbstractA reliable strategy to enhance the bonding ability in carbon reinforced aluminum laminates (CARALL) is proposed, which is based on the mechanical interlocking effect generated by the surface slot structure of aluminum alloy enhances the structural interface between fibers/resins and aluminum alloy. The characteristic of slot structure is determined, and the strengthening mechanism of bonding interfaces is revealed. The CARALL samples with slot structure are fabricated via an hot pressing process. The micro texture morphologies, mechanical, interlayer bonding properties under different conditions are studied. The results indicate that forming a slot structure on the aluminum surface is beneficial for improving the interfacial bonding performance. Compared with the non‐slotted structure, the interlayer type II fracture toughness of the slotted structure is increased by 112.99%. The slotted structure can reduce the defects at the interface between the layers and improve the interface bonding force. In this work, the interlaminar shear strength (ILSS) of the slotted structure sample was 27.08% higher than that of the non‐slotted structure sample.Highlights A slotted structure was proposed to solve the problem of insufficient bonding strength. A slotted structure consistent with the direction of adjacent fibers is designed. The interlayer type II fracture toughness of the slotted structure is increased by 112.99%. The final crack propagation of the slotted structure sample is reduced by 40%. The final failure area of the slotted structure sample is reduced by 53.85%.

Morphology-controlled ZnO nanoarrays in situ grown on the basalt fiber surface for improving the interfacial properties of the high-performance thermoplastic composites

In this work, a biomimetic root-soil-like interfacial phase structure was constructed to improve the weak interfacial bonding of the fibers and resin based on the mechanical interlocking theory. Unidirectional basalt fiber (BF) reinforced high-temperature resistant thermoplastic poly (phthalazinone ether nitrile ketone) (PPENK, Tg = 278 °C) composites with multiscale structures were prepared. By utilizing a whiskerization technique, the zinc oxide nanoarrays (ZnO-NAs) with controllable morphologies grown on the BF surface through a pyrolysis-hydrothermal method. The remarkable field emission properties of the ZnO-NAs allow for visually characterizing the interfacial phase structures. The flexural, interlaminar shear, and interfacial shear strengths of BF-ZnO-PEI-2/PPENK composite were increased by 43 %, 65 %, and 177 %, respectively. Further investigations revealed that the flexural strength retention was 61 % at 250 °C, respectively. This study introduces a novel and viable approach to enhance the interfacial properties of BF-reinforced high-performance thermoplastic composites and expands their applications within high-temperature environments.

Failure analysis of glass fiber and basalt fiber reinforced polymer composites under an extreme environment with high‐temperature, high‐pressure and H2S/CO2 exposure

AbstractFiber‐reinforced polymers composites (FRPs) are widely used in the industrial field, but their failure mechanism in extreme environments is usually unclear. In this work, the effect of high‐temperature, high‐pressure and H2S/CO2 extreme environment, similar to oil and gas field conditions, on raw fibers and unidirectional FRPs was investigated. The results showed that the glass fibers (GFs) suffered extensive degradation with the presence of metal sulfides in the precipitate, whereas basalt fibers (BFs) showed localized degradation. The flexural modulus of glass fiber reinforced polymer composite (GFRP) after degradation decreased by 28.8% compared to 25.6% for the basalt fiber reinforced polymer composite (BFRP). The interlaminar shear strength and flexural strength of the BFRP decreased by 20.3% and 24.7% respectively. In contrast, the GFRP had a reduction of 55.2% in flexural strength after degradation. Finite element method (FEM) analysis showed that the GFRP exhibited severe cohesive interface damage, while the primary failure mode of BFRP remained essentially unchanged with a combination of fiber damage and cohesive interface damage. This study confirms the superior degradation resistance of BF/BFRP over GF/GFRP in the simulated environment and highlights its promising application potential in oil and gas field service.Highlights Filament winding was used to fabricate the GFRP and BFRP. Revealed distinct surface morphology changes in GFs and BFs under simulated oil and gas field conditions. Superior degradation resistance of BFRP over GFRP was found in the extreme environment. Demonstrated superior chemical stability and mechanical properties of BFRP over GFRP. Used FEM to investigate the failure modes of FRPs before and after exposure.

Interlaminar Shear Strength Change and Storage Life Prediction of Carbon Fiber/Epoxy Composites with Hygrothermal Accelerated Aging.

In order to investigate the durability of fiber-reinforced polymer composites in hygrothermal environments, hygrothermal accelerate aging tests, for 360 days at 70 °C, RH70%; 70 °C, RH85%; 85 °C, RH70%; and 85 °C, RH85% and natural storage for 2 years in Guangzhou, China, were carried out for composite laminates. Then, the moisture absorption and interlaminar shear strength were measured. The hygrothermal damage mechanism of the composite was studied by Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FSEM). A dual stress storage life prediction model and the equivalent relationship between natural storage and hygrothermal acceleration were established. The results show that the order of moisture absorption rates, moisture absorption contents, and the severity effect order on the interlaminar shear strength is RH85%; 85 °C > 70 °C; RH85% > 85 °C; RH70% > 70 °C; and RH70%. The time to achieve an effective moisture absorption balance is opposite to this. The moisture absorption rate meets Fick's law before the effective moisture absorption balance, and then shows a linear trend. The interlayer shear strength still decreases exponentially with aging, which is mainly caused by the resin plasticization and interface weakening. Hygrothermal accelerated aging for 13.4831 days at 85 °C; RH85% is equivalent to that for one-year actual storage in Guangzhou. According to the failure criterion of shear strength decreasing to 77%, the storage life of T700/epoxy in Guangzhou is 14.4661 years.

Characteristics of in-situ automated fiber placement carbon-fiber-reinforced low-melt polyaryl ether ketone laminates part 1: Manufacturing influences

This study presents an investigation into mechanical and thermal properties, as well as the microstructure of Automated Fiber Placement-manufactured laminates using a novel carbon fiber-reinforced low-melt polyaryl ether ketone polymer material. The material’s lower melting temperature and lower melt viscosity as compared to established high-temperature thermoplastic materials as PEEK, promises favourable characteristics for the Automated Fiber Placement process. This work aims at in-situ consolidation and the influence of a heated tooling and a post process tempering step, which both turned out to be promising in previous investigations. Laminates were manufactured using a cold tooling, a heated tooling configuration, a cold tooling with a subsequent tempering process step and a hot-pressed reference laminate. Differential Scanning Calorimetry showed that crystallinity values more than doubled for the heated tooling and post process tempering configurations, compared to the cold tooling, reaching 24% and 30%, respectively. Mechanical strength values showed an increase in interlaminar shear strength and compression strength but did not increase to the same extent as was expected from the increase in crystallinity. With Scanning Electron Microscopy differences in the microscopic structure of the polymer matrix could be detected. While the post process tempering step leads to a mostly lamellar crystalline structure, the heated tooling configuration and the post process hot pressing induce a predominance of crystalline spherulites, which might positively affect the mechanical performance. Computed Tomography scans revealed a high amount of porosity in the in-situ-manufactured samples and unprocessed tape material, which likely mitigated the positive effect of increased crystallinity.

In-situ infrared annealing for laser-assisted automated fiber placement to enhance interlaminar properties without sacrificing laydown efficiency

Laser-assisted automated fiber placement (LAFP) in-situ consolidation (ISC) of thermoplastic composites suffers from poor interlaminar bonding. Repass treatment improves interlaminar bonding but sacrifices laydown efficiency. Here we propose an in-situ infrared annealing (IIA) strategy that combines infrared heat treatment with a second pressure roller immediately following the LAFP ISC process. This approach causes repeated interlaminar melting and slower cooling, reducing the porosity by 57.9% and increasing crystallinity by 89.2% compared to LAFP-manufactured carbon fiber-reinforced polyether-ether-ketone composites. Moreover, it completes the crystallization process with only a single placement rather than multiple placements by repass treatment. Interlaminar shear strength and mode I interlaminar fracture toughness are improved by 239.7% and 292.4%, respectively. These improvements are comparable to those achieved by repass treatment with a near-infrared laser. Overall, the IIA strategy offers a promising alternative to traditional post-consolidation processes while maintaining laydown efficiency.

Three‐point bending, interlaminar shear, and impact strength in bioinspired helicoidal basalt fiber/epoxy composites: A comparative experimental analysis

AbstractThis study investigates the mechanical characteristics of basalt fiber/epoxy polymer composites (BPC) inspired by nature's higher‐order designs especially helicoidal structures found in fish scales. The present work includes the experimental analysis of 20‐layered bioinspired BPC composites in single helicoidal ([90/80/70/60/50/40/30/20/10/0]s), and double helicoidal ([130/40/120/30/110/20/100/10/90/0]s) layups. The hand layup technique, followed by the vacuum bagging method, is used to fabricate composite laminates. The layup design significantly influenced the mechanical properties of both helicoidal structures with different stacking sequences, including load capacity, deformation, energy absorption, and fracture modes. Interestingly, failure mechanisms demonstrated both bending and twisting (attributed to specific ply orientation, resulting in a twisting effect) occurring majorly under flexural loading, leading to improved energy absorption. The flexural strength of single helicoidal laminate was observed to be 28.8% higher than double helicoidal laminate design. On the other hand, the double helicoidal laminate showed 46.8% and 19.4% higher interlaminar shear strength (ILSS) and impact resistance properties, respectively, compared to the single helicoidal laminate design. Therefore, this comparative experimental analysis of both stacking structures provides insights into potential changes in conventional stacking sequences and enhances understanding of mechanical responses in bioinspired composites.Highlights Mechanical characterization of bioinspired helicoidal laminates is done. The flexural strength of single helicoidal laminates is 28.8% higher than double helicoidal laminates. Double helicoidal laminates showed better interlaminar shear strength and energy absorption.

Effect of temperature on flexural and interlaminar shear strength properties of carbon‐epoxy composites: Experiment and modeling

AbstractCarbon fiber composites are known for excellent specific mechanical properties at room temperature. It is important to model the effect of temperature on flexural strength and interlaminar shear strength (ILSS). In this study, T700 carbon fiber composites with two different epoxy resins (Epofine, LY556) were prepared using filament winding and named as TE and TL composites. The dynamic mechanical analysis (DMA) tests revealed Tg of 177 and 192°C for TE and TL composites, respectively. Three‐point bending (flexural) and short‐beam shear (ILSS) tests were performed at −20, 0, RT, 90, 105, 150, 170, and 200°C. It was observed that flexural strength and ILSS decreases linearly with increase in temperature. Fracture analysis of flexural samples revealed fiber breakage at −20°C and micro‐buckling at elevated temperature are dominant failure mechanisms. Fracture analysis of ILSS samples showed delamination with microcracking at −20°C and plastic deformation of matrix at elevated temperature. A new empirical model was proposed to predict the temperature dependent flexural strength and ILSS. With this model, variation of flexure strength and ILSS with temperature can be estimated from respective values at RT, Tg and storage modulus values from DMA, thus extensive experimentation at high temperatures can be avoided.Highlights Mechanical properties of filament wound composites are tested from −20 to 200°C. Flexural strength and ILSS linearly decreases with increase in temperature. Fiber breakage at −20°C and micro bucking at 200°C are dominant in flexure. Delamination at −20°C and plastic deformation at 200°C are dominant in ILSS. Analytical model for finding temperature dependent flexural strength and ILSS.

An Experimental Study on the Hardness, Inter Laminar Shear Strength, and Water Absorption Behavior of Habeshian Banana Fiber Reinforced Composites

ABSTRACT The current study examines the effect of NaOH treatment on the hardness, inter-laminar shear strength (ILSS) and water absorption behavior of epoxy composites reinforced with banana pseudostem fibers. Using the hand-lay-up method, six distinct samples are created that are composed of layers of woven and short banana fibers in both a plain and hybrid form. Plain- treated woven composites reveal the highest hardness and ILLS properties followed by the hybrid and short fiber composites. The random orientation of the fiber structure in short fiber composites results in the largest moisture absorption; this behavior is further supported by elucidating the kinetic parameters and diffusion coefficient parameters. SEM analysis confirms the improved surface of the NaOH-treated composite material.