Effects of kenaf contents and fiber orientation on physical,mechanical, and morphological properties of hybrid laminated composites for vehicle spall liners

The aim of this work is to study the effect of kenaf volume content and fiber orientation on tensile and flexural properties of kenaf/Kevlar hybrid composites. Hybrid composites were prepared by laminating aramid fabric (Kevlar 29) with kenaf in three orientations (woven, 0^o/90^o cross ply uni‐directional (UD), and non‐woven mat) with different kenaf fiber loadings from 15 to 20% and total fiber loading (Kenaf and Kevlar) of 27–49%. The void content varies between 11.5–37.7% to laminate with UD and non‐woven mat, respectively. The void content in a woven kenaf structure is 16.2%. Tensile and flexural properties of kenaf/Kevlar hybrid composites were evaluated. Results indicate that UD kenaf fibers reinforced composites display better tensile and flexural properties as compared to woven and non‐woven mat reinforced hybrid composites. It is also noticed that increasing volume fraction of kenaf fiber in hybrid composites reduces tensile and flexural properties. Tensile fracture of hybrid composites was morphologically analysed by scanning electron microscopy (SEM). SEM micrographs of Kevlar composite failed in two major modes; fiber fracture by the typical splitting process along with, extensive longitudinal matrix and interfacial shear fracture. UD kenaf structure observed a good interlayer bonding and low matrix cracking/debonding. Damage in composite with woven kenaf shows weak kenaf‐matrix bonding. Composite with kenaf mat contains the high void in laminates and poor interfacial bonding. These results motivate us to further study the potential of using kenaf in woven and UD structure in hybrid composites to improve the ballistic application, for example, vehicle spall‐liner. POLYM. COMPOS., 36:1469–1476, 2015. © 2014 Society of Plastics Engineers     

Experimental characterization of traditional composites manufactured by vacuum‐assisted resin‐transfer molding

The primary purpose of this study is to investigate the anisotropic behavior of different glass‐fabric‐reinforced polyester composites. Two commonly used types of traditional glass fabrics, woven roving fabric and chopped strand mat, have been used. Composite laminates have been manufactured by the vacuum infusion of polyester resin into the fabrics. The effects of geometric variables on the composite structural integrity and strength are illustrated. Hence, tensile and three‐point‐bending flexural tests have been conducted at different off‐axial angles (0, 45, and 90°) with respect to the longitudinal direction. In this study, an important practical problem with fibrous composites, the interlaminar shear strength as measured in short‐beam shear tests, is discussed. The most significant result deduced from this investigation is the strong correlation between the changes in the interlaminar shear strength values and fiber orientation angle in the case of woven fabric laminates. Extensive photographs of fractured tensile specimens resulting from a variety of uniaxial loading conditions are presented. Another aim of this work is to investigate the interaction between the glass fiber and polyester matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, are interpreted in an attempt to explain the interaction between the glass fiber and polyester. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Research on the mechanical properties prediction of carbon/epoxy composite laminates with different void contents

The influence of the porosity on the static mechanical strength of the carbon fiber fabric reinforced epoxy composites laminates was investigated. The tensile, compressive, bending, and interlaminar strength test on the CFRP laminates with porosity of 0.33% and 1.50% were conducted and simulated by a finite element analysis model. The article proposes the failure criterion of the static mechanical strength of the fabric fiber reinforced composites based on the improved Hashin failure criterion that is suitable for the undirectional composite laminates. The basic composite strength parameters are used to evaluate the mechanical properties of CFRP laminates with different porosities. A finite element analysis model is established by using software ABAQUS™ combined with the sudden stiffness degradation model. The experiment results show that the tensile, compressive, bending, and interlaminar strength decrease with the increasing porosities. The tensile, compressive, bending, and interlaminar strength of the fabric carbon fiber reinforced epoxy composites laminates are simulated accurately by the finite element model. POLYM. COMPOS., 14–20, 2016. © 2014 Society of Plastics Engineers     

Hybridization effects on tensile and bending behavior of aramid/basalt fiber reinforced epoxy composites

In this study, the mechanical properties of aramid/basalt hybrid composite laminates were determined, and the effects of hybridization on the mechanical properties were investigated. To examine the effect of hybridization, the mechanical properties of aramid/basalt hybrid composite laminates were compared with those of aramid/epoxy and basalt/epoxy non‐hybrid composite laminates. The mechanical properties, tensile and flexural, of composite laminates were determined by performing uniaxial tensile and three‐point bending tests. The results showed that the employment of basalt fibers for partial substitution of aramid fibers in the composite laminate could provide improvements in the tensile and flexural properties. Furthermore, the results of three‐point bending tests were found that the employment of basalt fibers on compressive side across the thickness of composite laminates were realized significant improvement for flexural properties in comparison to the employment of basalt fibers on tensile side. POLYM. COMPOS., 38:1144–1150, 2017. © 2015 Society of Plastics Engineers     

Effect of loading‐unloading cycles on impact‐damaged jute/glass hybrid laminates

The production of glass/plant fiber hybrid laminates is a possibility for obtaining semistructural materials with sufficient impact properties, and a better life cycle analysis (LCA) profile than fiberglass. The simplest and possibly the most effective configuration for the production of these hybrids would involve the use of a plant fiber reinforced laminate as the core between two glass fiber reinforced laminates. A main limitation to the use of composites including plant fibers is that their properties may be significantly affected by the presence of damage, so that even the application of a low stress level can result in laminate failure. In particular, it is suggested that when loading is repeatedly applied and removed, residual properties may vary in an unpredictable way. In this work, E‐glass/jute hybrid reinforced laminates, impacted in a range of energies (10, 12.5, and 15 J), have been subjected to post‐impact cyclic flexural tests with a step loading procedure. This would allow evaluating the effect of damage dissipation offered by the plant fiber reinforced core. The tests have also been monitored by acoustic emission (AE), which has confirmed the existence of severe limitations to the use of this hybrid material when impacted at energies close to penetration. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Effect of patch hybridization on the tensile behavior of patch repaired glass/epoxy composite laminates using acoustic emission monitoring

This paper investigates the tensile response of damaged glass/epoxy composite laminates repaired using hybrid external patches. Hybrid external patches based on glass and Kevlar woven fabrics bonded on both faces of the damaged parent laminate were considered. Five different kinds of plain weave woven fabrics with a different ratio between glass and Kevlar fibers (100/0, 75/25, 50/50, 25/75 and 0/100) were used as the external patches. The intention of using these hybrid patches was to combine the excellent tensile stiffness of Kevlar fiber with the superior resin adhesion property of glass fiber. The virgin and damaged specimens were taken as the reference specimens for comparison of residual mechanical properties and damage mechanisms. Damage evolution and the failure progression of the repaired glass/epoxy specimens were monitored using real-time Acoustic Emission (AE) monitoring technique. The Acoustic Emission (AE) results depict different damage profiles and link them with mechanical test results to reveal the load to a change in failure mechanisms during mechanical loading concerning the influence of each hybrid patches on the performance of repaired glass/epoxy specimens. Good correlation of the acoustic emission results with the photographic images of fractured specimens was obtained. Specimens repaired with the equal volume fraction of glass and Kevlar fibers in the external patches presented the most favorable residual tensile response by effectively releasing the stress concentration in the damaged area.     

Concentration effect of γ‐glycidoxypropyltrimethoxysilane on the mechanical properties of glass fiber–epoxy composites

In this study, glass fibers were modified using γ‐glycidoxypropyltrimethoxysilane of different concentrations to improve the interfacial adhesion at interfaces between fibers and matrix. Effects of γ‐glycidoxypropyltrimethoxysilane on mechanical properties and fracture behavior of glass fiber/epoxy composites were investigated experimentally. Mechanical properties of the composites have been investigated by tensile tests, short beam tests, and flexural tests. The short‐beam method was used to measure the interlaminar shear strength (ILSS) of laminates. The tensile and flexural properties of composites were characterized by tensile and three‐point bending tests, respectively. The fracture surfaces of the composites were observed with a scanning electron microscope. On comparing the results obtained for the different concentrations of silane solution, it was found that the 0.5% GPS silane treatment provided the best mechanical properties. The ILSS value of heat‐cleaned glass fiber reinforced composite is enhanced by ∼59% as a result of the glass fiber treatment with 0.5% γ‐GPS. Also, an improvement of about 37% in tensile strength, about 78% in flexural strength of the composite with the 0.5% γ‐GPS treatment of glass fibers was observed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

The fracture properties of a smart fiber metal laminate

This paper investigates the interfacial, tensile, and fatigue properties of a novel smart fiber‐metal laminate (FML) based on a nickel‐titanium (Ni‐Ti) shape memory alloy and a woven glass fiber reinforced epoxy. Initial tests, using the single cantilever beam (SCB) geometry, have shown that this unique system offers high values of metal‐composite interfacial fracture toughness. Tensile tests have shown that the mechanical properties of these FMLs lie between those offered by its constituent materials and that their tensile modulus and strength can be easily predicted using a rule of mixtures approach. Tension‐tension fatigue tests have shown that the fatigue performance of notched smart FMLs is superior to that offered by the plain Ni‐Ti alloy. A subsequent optical examination of unnotched laminates tested to failure under tension‐tension fatigue loading has shown that the fracture mechanisms occurring within the Ni‐Ti FMLs are strongly dependent on the applied cyclic stress. POLYM. COMPOS., 28:534–544, 2007. © 2007 Society of Plastics Engineers     

The comparison of low‐velocity impact resistance of aluminum/carbon and glass fiber metal laminates

This article presents the low‐velocity impact response of fiber metal laminates, based on aluminum with a polymer composite, reinforced with carbon and glass fibers. The influence of fiber orientations as well as analysis of load‐time history, damage area and damage depth in relation to different energy levels is presented and discussed. The obtained results made it possible to determine characteristic points, which may be responsible for particular stages of the laminate structure degradation process: local microcracks and delaminations, leading to a decrease in the stiffness of the laminate, as well as further damage represented by laminate cracks and its perforation. The damage mechanism of fiber metal laminates is rather complex. In case of carbon fiber laminates, a higher tendency to perforation was observed in comparison to laminates containing glass fibers. Delaminations in composite interlayers and at the metal/composite interface constitute a significant damage form of fiber metal laminates resulting from dynamic loads. Fiber metal laminates with glass fibers absorb energy mainly through plastic deformation as well as through delamination initiation and propagation, whereas laminates containing carbon fibers absorb energy for penetration and perforation of the laminate. POLYM. COMPOS. 37:1056–1063, 2016. © 2014 Society of Plastics Engineers     

Fabrication and mechanical response of commingled GF/PET composites

The mechanical properties and the response to mechanical load of continuous glass fiber reinforced polyethylene terephthalate (GF/PET) laminates have been characterized. The laminates were manufactured by compression molding stacks of novel woven and warp knitted fabrics produced from commingled yarns. The laminate quality was examined by means of optical and scanning electron microscopy. Few voids were found and the laminate quality was good. Resin pockets occurred in the woven laminates, originating from the architecture of the woven fabric. The strength of the fiber/matrix interface was poor. Some problems were encountered while manufacturing the laminates. These led to fiber misalignment and consequently resulted in tensile mechanical properties that were slightly lower than expected. Flexural failures all initiated as a result of compression, and it is possible that the compression strength of the matrix material, rather than its tensile strength, might limit the ultimate mechanical performance of the composites. Flexural failures for both materials were very gradual. The warp knitted laminates were stronger and stiffer than the woven laminates. The impact behavior was also investigated; the woven laminates exhibited superior damage tolerance compared with the warp knitted laminates.     

Comparison of tensile and compressive characteristics of intra/interply hybrid laminates reinforced high‐density flexible foam composites

The current study focused on fabrication and mechanical evaluation of intra/interply hybrid laminates – reinforced high‐density flexible foam composites. The effects of composite thickness and expansion factor on the tensile and compressive characterization of the hybrid ‐ laminated composites were experimentally investigated. Double face sheets were made of high‐strength intra/interply hybrid laminates containing recycled Kevlar nonwovens and glass woven fabric. The results revealed that the hybrid laminates face sheet apparently promoted the tensile strength and tear resistance of the high ‐ density flexible polyurethane foam. Tearing resistance in perpendicular direction exceeded more than twice the value in parallel direction. In terms of dynamic cushioning properties, cushioning force increased with the increase in composite thickness and the decrease in expansion factor , whereas the cushioning capacity loss, however, showed a different trend with the variation of the parameters. Most samples buffered more than 95% incident force under dynamic loading. Composite thickness and expansion factor exhibited significant influence on compression and indentation properties, including hardness, initial hardness factor , and indentation modulus. Except the composites with 10 mm thickness, the intra/interply hybrid laminated composites exhibited hysteresis loss of indentation force deflection ranging from approximately 30 to 38%, which was due to the fiber and thermal bonding point failure of hybrid laminates as unrecoverable damage. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41438.     

Comparison of mechanical properties of epoxy composites reinforced with stitched glass and carbon fabrics: Characterization of mechanical anisotropy in composites and investigation on the interaction between fiber and epoxy matrix

The primary purpose of the study is to evaluate and compare the mechanical properties of epoxy‐based composites having different fiber reinforcements. Glass and carbon fiber composite laminates were manufactured by vacuum infusion of epoxy resin into two commonly used noncrimp stitched fabric (NCF) types: unidirectional and biaxial fabrics. The effects of geometric variables on composite structural integrity and strength were illustrated. Hence, tensile and three‐point bending flexural tests were conducted up to failure on specimens strengthened with different layouts of fibrous plies in NCF. In this article, an important practical problem in fibrous composites, interlaminar shear strength as measured in short beam shear test, is discussed. The fabric composites were tested in three directions: at 0°, 45°, and 90°. In addition to the extensive efforts in elucidating the variation in the mechanical properties of noncrimp glass and carbon fabric reinforced laminates, the work presented here focuses, also, on the type of interactions that are established between fiber and epoxy matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, were interpreted in an attempt to explain the failure mechanisms in the composite laminates broken in tension. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Structure–properties relations in titanium‐based thermoplastic fiber–metal laminates

This paper investigates the interfacial, tensile, and fatigue properties of a titanium alloy fiber–metal laminate (Ti‐FML) based on woven glass‐fiber‐reinforced polyetherimide (GF/PEI). Initial tests, using the single cantilever beam (SCB) geometry have shown that it is not necessary to surface treat the titanium alloy in order to achieve a high value of metal–composite interfacial fracture toughness. Tensile tests have shown that the mechanical properties of the FML lie between those offered by its constituent materials. Tension–tension fatigue tests have shown that the fatigue lives of these laminates are superior to those offered by the plain titanium alloy. The mechanical properties of this glass fiber/PEI FML have also been compared with those offered by an FML based on a unidirectional carbon‐fiber‐reinforced polyetheretherketone (CF/PEEK) composite. Here, it has been shown that although the fatigue properties of this woven GF/PEI composite are inferior to those of the CF/PEEK FML, they do offer a higher temperature capability due to the higher glass transition temperature of the PEI matrix. Polym. Compos. 27:264–270, 2006. © 2006 Society of Plastics Engineers.     

Polyester composites reinforced with noncrimp stitched carbon fabrics: Mechanical characterization of composites and investigation on the interaction between polyester and carbon fiber

The primary purpose of the study is to investigate the anisotropic behavior of different noncrimp stitched fabric (NCF) reinforced polyester composites. Carbon fiber composite laminates were manufactured by vacuum infusion of polyester resin into two commonly used advanced noncrimp stitched carbon fabric types, unidirectional and biaxial carbon fabric. The effects of geometric variables on composite structural integrity and strength were illustrated. Hence, tensile and three‐point bending flexural tests were conducted up to failure on specimens strengthened with different layouts of fibrous plies in NCF. In this article an important practical problem in fibrous composites, interlaminar shear strength as measured in short beam shear tests, is discussed. The fabric composites were tested in three directions: at 0°, 45°, and 90°. Extensive photomicrographs of multilayered composites resulting from a variety of uniaxial loading conditions were presented. It was observed that broken fibers recede within the matrix in composites with weak interfacial bond. Another aim of the present work was to investigate the interaction between carbon fiber and polyester matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, were interpreted in an attempt to explain the instability of polyester‐resin–carbon‐fiber interfaces. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4554–4564, 2006     

Low‐cost,environmentally friendly route to produce glass fiber‐reinforced polymer composites with microfibrillated cellulose interphase

In this article, an easy, effective, and eco‐friendly method to improve the mechanical performance of glass fiber‐reinforced polymer composites is proposed, which involves the coating of unsized glass fiber fabric layers by simple immersion in an aqueous suspension containing sugarcane bagasse microfibrillated cellulose (MFC), followed by vacuum‐assisted liquid resin infusion as the processing method. From atomic force microscopy, a 250 nm MFC‐rich interphase was found, revealing its ability to build micro‐ and nanobridges acting as bulk epoxy matrix and GF linker. The interlaminar shear strength, quasi‐static tensile, and flexural tests, as well as the morphological and fractographic inspection of test coupons containing the secondary substructure, broadly supported the assumption of the efficient role on the interfacial level of this nano reinforcement by enhancing the load transference and distribution from the polymer matrix to the main reinforcing fiber system compared to baseline unsized fiber‐reinforced epoxy laminates. This finding permits this class of composite materials to be considered as having great potential to achieve products with excellent performance/cost ratios. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44183.     

Pultruded fiber reinforced thermoplastic poly(methyl methacrylate) composites. Part II: Mechanical and thermal properties

A novel process has been developed to manufacture poly(methyl methacrylate) (PMMA) pultruded parts. The mechanical and dynamic mechanical properties, environmental effects, postformability of pultruded composites and properties of various fiber (glass, carbon and Kevlar 49 aramid fiber) reinforced PMMA composites have been studied. Results show that the mechanical and thermal properties (i.e. tensile strength, flexural strength and modulus, impact strength and HDT) increase with fiber content. Kevlar fiber/PMMA composites possess the highest impact strength and HDT, while carbon fiber/PMMA composites show the highest tensile strength, tensile and flexural modulus, and glass fiber/PMMA composites show the highest flexural strength. Experimental tensile strengths of all composites except carbon fiber/PMMA composites follow the rule of mixtures. The deviation of carbon fiber/PMMA composite is due to the fiber breakage during processing. Pultruded glass fiber reinforced PMMA composites exhibit good weather resistance. They can be postformed by thermoforming, and mechanical properties can be improved by postforming. The dynamic shear storage modulus (G′) of pultruded glass fiber reinforced PMMA composites increased with decreasing pulling rate, and G′ was higher than that of pultruded Nylon 6 and polyester composites.     

芳纶针织物复合材料力学性能研究

为探究芳纶针织物复合材料的力学性能,用电子织物强力机对平板硫化机制得的芳纶针织物复合材料进行拉伸、弯曲、压缩性能测试,结果表明:芳纶针织物增强复合材料为非脆性破坏;经硅烷偶联剂处理有效地提高了芳纶针织物增强复合材料的抗拉、抗弯、抗压强度;罗纹空气层组织的抗拉、抗弯及抗压性能优于满针罗纹组织。     

Mechanical properties of glass fiber/organic fiber mixed–mat reinforced thermoplastic composites

The purpose of this study is to investigate the influence of different types of fibers on the mechanical properties of hybrid composite materials. Long and short glass fibers (GF) and different types of organic fibers, viz. aramid fiber, DuPont Kevlar‐49 (KF), liquid crystalline polymer (LCP), and vinylon (VF) in hybrid composites, were used to reinforced the high density polyethylene (HDPE) matrix. The long fiber hybrid composites were prepared in a “fiber separating and flying machine,” while the short fiber hybrid composites were prepared in an “elastic extruder.” The total amount of fibers used in both long and short fiber hybrid composites was fixed at 20 vol%. The influence of fiber content, length, and mixing ratio on mechanical properties, such as tensile, bending, Izod and high rate impact strength, as well as viscoelastic propertics in the solid state, was studied. Fracture surfaces of the materials were also examined using a scanning electron microscopy.     

Effect of thermal shock cycling on the quasi-static and dynamic flexural properties of flax fabric-epoxy matrix laminates

The aim of the present work is to investigate the influence of thermal shock cycling on the quasi-static and dynamic flexural properties of epoxy matrix composites reinforced with natural flax fibers fabric. Polymer composite laminates reinforced with four plies of natural flax fiber fabric have been manufactured. The samples have been exposed to different number of thermal shock cycles (0, 50, 100, 200, 300, 400), at a temperature range from −40 °C to +28 °C. Dynamic mechanical analysis (DMA) tests were performed on both pristine and thermally shocked specimens in order to determine their viscoelastic response. Due to the thermal shock cycling and after 100 thermal shock cycles, a maximum decrease in storage and loss modulus on the order of 50% was observed. After 100 thermal shock cycles, no further degradation of dynamic properties was observed. On the contrary, damping factor and glass transition temperature values showed a minor variation as number of thermal shock cycles increased. In addition, the time–temperature superposition principle (TTSP) was successfully applied, confirming the fact that the flax fiber fabric-epoxy laminate is a thermo-rheologically simple material. Likewise, quasi-static three-point bending tests were executed and a maximum decrease of 20% in flexural strength was observed after 400 thermal shock cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48529.     

Investigations on physical,mechanical, morphological and water absorption properties of ramie/hemp/kevlar reinforced vinyl ester hybrid composites

Structural uses in the vehicle, aerospace, and sporting goods industries are being supplanted by hybrid composites that utilized natural fibers as reinforcements. The main focus of this work is to fabricate and characterize the ramie, hemp, and kevlar fabric reinforced hybrid vinyl ester composites. The composite laminates were fabricated via economically feasible and flexible hand lay-up technique. Overall six composites were prepared by varying the stacking sequence, including both hybrid and non-hybrid composites. The prepared composites were subjected to physical analysis (density, void fraction), mechanical tests (tensile, flexural, interlaminar shear, and impact test), morphological analysis (scanning electron microscopy), and water absorption test. The hybrid composites exhibited lesser void percentage than the non-hybrid composites. The mechanical properties were maximum for kevlar fabric skinned with core natural fabric reinforced composites (L-5, L-6) due to hybridization of highly strengthened kevlar fabrics. Moreover, the number fabric layers reinforced to achieve the standard thickness also affected the mechanical properties. All composite morphologies exhibited the same failure characteristics, including transverse interlaminar shear cracking, microbuckling, and fiber rip. The texture of the Kevlar yarns is uniform, but the texture of the natural fabric yarns is relatively less uniform. In comparison to the salt water medium, the percentage of water absorbed by composites in normal and distilled water was greater. This is due to the presence and accumulation of salt particles on the surface of the materials, which inhibits the action of water molecules, resulting in a drop in the proportion.