Novel,low-cost jute-polyester composites. Part 1: Processing,mechanical properties,and SEM analysis

The development of high performance composites from a cheap natural fiber, jute, as reinforcement is particularly significant from an economic point of view. In this work, jute fiber-unsaturated polyester(GP) composites having appreciable mechanical properties were prepared by using solution impregnation and hot curing methods. Both unbleached (control) and bleached jute slivers with various percentages of fiber loadings were used to prepare the composites and were named JPH (C) i.e., Jute Polyester Hot Curing (control), and JPH (B) i.e., Jute Polyester Hot Curing (bleached), respectively. Mechanical properties such as tensile and flexural strain, toughness, and moduli of both the grades have been compared. Composites having 60 wt% of jute fiber yielded the best results. JPH (B) showed much better flexural properties than JPH (C), although the tensile properties of the latter were better. The inter-laminar shear strength (ILSS) of the JPH (B) was found to be higher than JPH (C). The nature of fiber-resin bonding was studied from scanning electron micrographs of the specimens subjected to tensile and flexural fracture. Dynamic mechanical properties were found to be very high, superior even to those of glass fiber reinforced composites. The flexural storage modulus was found to be 12.3 GPa at 30°C and to decrease slowly with temperature. The major finding in this work is the attainment of high mechanical properties of composite specimens with 60 wt %fiber loading. On a weight and cost basis, bleached jute fibres were found to be better reinforcements than other fibers with usual surface modification by coating or grafting processes.     

Experimental analysis and theoretical modeling of the mechanical behavior of short glass fiber and short carbon fiber reinforced polycarbonate hybrid composites

In this research, polycarbonate (PC) composites with short glass fiber (SGF) and short carbon fiber (SCF) hybrid fiber reinforcements were compounded by single screw extruder and specimens were prepared by injection molding machine. This article aims to investigate the mechanical properties of PC hybrid composites, by means of the experimental and the theoretical methods. The composites were subjected to tensile test. Experimental results showed the improvements in tensile strength and modulus by increasing the SCF content of the hybrid composite. The theoretical tensile strength was predicted based on Kelly–Tyson model and rule of hybrid mixture. Kelly–Tyson model showed to be a good approximation to predict the tensile strength of composite. When the SCF was replaced by milled carbon fiber (MCF) to form a PC/SGF/MCF hybrid system, poorer mechanical properties are reported due to the weaker interfacial adhesion between MCF and PC, as proven by the scanning electron microscopy. POLYM. COMPOS., 37:1238–1248, 2016. © 2014 Society of Plastics Engineers     

玻纤增强基材的创新与发展

分析了当今下游复合材料工业的发展对玻纤增强基材发展的需要。重点介绍了风电叶片用玻纤纱、技术织物、复合织物、预浸渍制品、预成型增强体等各类玻纤增强基材以及增强热塑性塑料用的短切纤维、混合纱、LFT、GMT、GMT-D、LFT—D、增强热塑性片材等各类玻纤增强基材。并为玻纤增强基材如何促进这两类复合材料产品的发展提出建议。     

Stiffness and thermal expansion predictions for hybrid short fiber composites

A model is developed to predict thermal expansion coefficients and elastic moduli of multi-component (hybrid) composites. The model includes the influences of fiber aspect ratio; isotropic and anisotropic fiber materials; planar, three-dimensional or arbitrary fiber orientation; hollow and solid spherical reinforcements; and voids. The first step in the procedure is to predict the properties of an aligned-fiber single-reinforcement composite for each reinforcement type. Various micro-mechanics approaches are used, depending on the type of reinforcement. A simplified version of Lee and Westmann's theory is found to work well for hollow spherical reinforcements. Performing an orientation average accounts for the spatial orientation of each reinforcement, then an aggregate averaging procedure combines the single-reinforcement properties to model the hybrid. Predictions of the model compare favorably to experimental elastic and thermal properties of short fiber/hollow sphere composites designed for very high speed integrated circuit (VHSIC) board applications.     

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     

Mechanical and viscoelastic properties of soybean oil thermoset reinforced with jute fabrics and carded lyocell fiber

Composites and hybrid composites were manufactured from renewable materials based on jute fibers, regenerated cellulose fibers (Lyocell), and thermosetting polymer from soybean oil. Three different types of jute fabrics with biaxial weave architecture but different surface weights, and carded Lyocell fiber were used as reinforcements. Hybrid composites were also manufactured by combining the jute reinforcements with the Lyocell. The Lyocell composite was found to have better mechanical properties than other composites. It has tensile strength and modulus of about 144 MPa and 18 GPa, respectively. The jute composites also have relatively good mechanical properties, as their tensile strengths and moduli were found to be between 65 and 84 MPa, and between 14 and 19 GPa, respectively. The Lyocell‐reinforced composite showed the highest flexural strength and modulus, of about 217 MPa and 13 GPa, respectively. In all cases, the hybrid composites in this study showed improved mechanical properties but lower storage modulus. The Lyocell fiber gave the highest impact strength of about 35 kJ/m², which could be a result of its morphology. Dynamic mechanical analysis showed that the Lyocell reinforced composite has the best viscoelastic properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Shear behavior of soft-matrix composites reinforced with polyethylene loop-formed fibers

A soft material is defined as a substance that its mechanical properties depend on ambient conditions, e.g. external stresses, temperature, etc. Since composite structures with soft-material matrix do not have adequate pullout resistance with flat-type reinforcements such as fibers, there are a large number of cases where reinforcements with passive resistance are used in conjunction with ordinary fibers. Randomly distributed loop-formed fiber (RDLFF) is a novel idea to reinforce these types of composite materials. Therefore, the main aim of this paper is to use polyethylene RDLFF elements in soft-matrix composites. First, shear behavior of polyethylene RDLFF-reinforced composite was modeled with the use of force-equilibrium method, and then it was compared with that of flat-polyethylene fiber. In the next step, a set of laboratory direct shear tests was conducted on different samples including the neat treatment, polyethylene RDLFF and polyethylene fiber-reinforced composites. Thus, it was shown that through the shearing, a loop-formed fiber has two reinforcing effects including the “fiber effect” and the “loop effect”. The “loop effect” is the main advantage of using RDLFF to ordinary fibers at the same orientation and it is also the major difference in using the two kinds of fibers. The proposed model also indicated that the number of looped-form fibers, fiber diameter, coefficient of friction between fiber and matrix, loop dimension, tensile modulus of fiber, shearing zone and vertical compressive stress determine the shear resistance of RDLFF-reinforced composite. Therefore, the proposed model adequately predicts the shear behavior of soft-matrix composites reinforced with fibers and/or loop-formed fibers.     

High-Temperature Flow Behavior of SiC-Glass Composites in Compression and Tension

The high-temperature flow behavior of different borosilicate composites was investigated in compression and tension. The flow behavior of composites changed from Newtonian to non-Newtonian as the volume fraction and aspect ratio of reinforcements increased. Generally, platelet/particulate composites exhibited higher tensile elongations compared with short fiber/whisker composites. The tensile ductility increased with decreased volume fraction of reinforcements and temperature. Cavitation in these samples varied across the length, and maximum cavitation occurred near the fracture zone.     

改性芳纶纬编增强体复合材料力学性能的研究

为探讨芳纶纬编增强体复合材料的力学性能,以对位芳纶为原料,采用LiCl/无水乙醇溶液对芳纶表面进行改性处理,设计并编织1+1满针罗纹和罗纹空气层2种组织织物增强体,以E-51环氧树脂为基体,应用手糊成型技术制备芳纶纬编增强体平板复合材料。采用YG026D型电子织物强力机对制备的芳纶纬编增强体复合平板材料的经纬向拉伸、弯曲、压缩以及层间剪切性能进行测定。结果显示:经LiCl/无水乙醇络合溶液处理的芳纶纬编增强体复合材料的各项力学性能均有所提高,且经向的各项力学性能优于纬向。在拉伸、弯曲性能方面,罗纹空气层芳纶纬编增强体平板复合材料优于1+1满针罗纹芳纶纬编增强体复合材料。     

Piezoresistive behavior of epoxy matrix‐carbon fiber composites with different reinforcement arrangements

In this work, the self‐monitoring capability of epoxy matrix‐carbon fiber composites has been studied. Different concentrations and arrangements of reinforcements were used, including random chopped, unidirectional and bi‐directional continuous carbon fibers, weaved and nonweaved. Mechanical properties were determined by uniaxial tensile tests. The composite electric to mechanical behavior was established by determining its electrical resistivity variation as a function of the stress‐strain curve. It was observed that the composites electrical resistance increased during tensile tests, a trend that indicates piezoresistive behavior. The increase was linear for the chopped reinforced composites, while it exhibits different slopes in the continuous reinforced composites. The initial smaller slope corresponds mainly to separation of the 90° oriented fibers and/or transversal cracking of the matrix, whereas the latter higher slope is caused by fiber fracture. The results demonstrated how each reinforcement configuration exhibited a unique and typical electrical response depending on the specific reinforcement, which might be appropriate either for strain‐monitoring or damage‐monitoring. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Moisture absorption behavior and its effect on the mechanical properties of jute‐reinforced epoxy composite

With the growing economic competition and the ecological pressure, the past decade has seen a renewed interest in developing more efficient reinforcements along with overall production cost. In some industrial applications, natural fiber composites fulfill small requirements for making the product to be economical due to their several advantages such as low density, greater deformability, lower abrasiveness, and cost. In the present work, composites are prepared with epoxy as a resin and jute as reinforcement by hand lay‐up technique. Moisture absorption characteristics when exposed to saline water, mineral water, sub‐zero temperature conditions, and also effect of moisture on depreciation in strength (tensile strength and flexural strength) and of different layers (one, two, three layers) of composites are studied experimentally. Specimen preparation and testing were carried out as per ASTM standards. It is found that the jute‐reinforced epoxy composite give encouraging results when compared with the pure epoxy composites. The less effect in strength is observed after exposure to mineral water and sub‐zero temperature condition. The morphologies of the composites are also studied by scanning electron microscope. POLYM. COMPOS., 38:516–522, 2017. © 2015 Society of Plastics Engineers     

Effect of Plasma Treatment of Polyethylene Fibers on Interface and ementitious Composite Properties

It is well known that interfaces in composites play an important role in determining composite properties. In this paper, preliminary results of the improvement in tensile properties of a fiber-reinforced cementitious composite due to plasma treatment of the discontinuous polyethylene fibers are reported. Specific focus is placed on the pseudo strain-hardening composite properties induced by fiber reinforcements and associated load transfer from crackbridging fibers to matrix. Single fiber pullout tests support that the composite property improvement is indeed derived from interfacial property enhancement of the plasma treatment process.     

Industrial applications and properties of short glass fiber-reinforced plastics

Short glass fibers for reinforcements of plastics have been commercially produced for over three decades. During this period, they have been used in virtually every polymer, as well as in other matrices, such as concrete and plaster. Their tensile strength/cost performance is still three times that of Kevlar® and more than 30 times better than carbon fibers. Similarly, excellent modulus/cost performance and high temperature/cost performance can be achieved. This article gives a review of short-fiber composites: their properties and use. Included is a comparison of compounding vs. in-house blending, fiber/flake hybrids, and reinforced polymer blends. Finally, several new materials still in development stages will be examined.     

Tear resistance of sparsely reinforced elastomer sheets

A family of elastomer composites has been developed which has outstanding tear resistance, and good tensile strength and elongation to failure as measured in a standard tensile test. These composites constitute a family in that they all are sparsely reinforced by a fishnet-like webbing of reinforcement. The members of the family differ in that the reinforcements can be as flexible as soft polyurethane rod or as stiff as carbon fiber with 3000 strands per fiber. All these composites produce outstanding tear strength and an increase in the elongation to failure in an ASTM Die-C type of tear test. The intersections of the polyurethane rod reinforcements prove to be effective crack arrestors.     

Synergistic strengthening effect of graphene-carbon nanotube hybrid structure in aluminum matrix composites

High-performance reinforcement and tailored architecture are currently explored to develop advanced metal matrix composites. In this work, aluminum (Al) matrix composite reinforced by hybrid carbon nanofillers was fabricated by a composite flake assembly process. It was found that for various carbon nanofiller volume fractions, a striking synergistic strengthening effect was achieved by employing graphene (reduced graphene oxide, RGO) and carbon nanotube (CNT) hybrid structure as reinforcement in the Al matrix. Particularly, a tensile strength of 415 MPa was achieved with the addition of 1.5 vol.% of RGO-CNT hybrid, which is significantly higher than those reinforced by individual CNT or RGO (326 and 331 MPa, respectively). The synergistic strengthening effect was attributed to the formation of a planar network of RGO and CNT, which improves the load transfer efficiency between the matrix and the reinforcement in composites. Our study highlights the importance of reinforcement architecture for enhancing the strengthening ability in composites, and provides an effective route to fully take the advantage of the superior properties of various reinforcements.     

Evaluation of embedded optical fiber sensors in composites: EFPI sensor fabrication and quasi‐static evaluation

This article reports on the fabrication and evaluation of extrinsic Fabry–Perot interferometric (EFPI) sensors when embedded in fiber‐reinforced composites and tested under quasi‐static tensile and compressive mechanical loading. The EFPI strain sensors were embedded in carbon fiber composite test specimens, and their performance was compared against a surface‐mounted extensometer and electrical resistance strain gauges. When the composite was subjected to quasi‐static tensile loading, the sensors failed around a strain level of 0.5%; under compressive loading, the sensors survived until the failure of the composite at 1.1% strain. The EFPI sensors used in this study were fabricated in‐house and the issues relating to fabrication are discussed in the context of their performance when embedded in composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Polymerization compounding of HDPE/Kevlar composites. I. Morphology and mechanical properties

The aim of this work is to perform the polymerization compounding to improve the properties of Kevlar/PE composites. The approach consists in involving the surface of a reinforcement in a polymerization process of a polymer to be used either as a matrix in the final composite or as a special surface treatment to enhance solid/polymer interface properties in the composite. The polymerization compounding process is illustrated here with the polyaramid fibers as reinforcements and polyethylene as a matrix. The number of active sites on the fiber surface, initially insufficient to anchor the catalyst, were increased by a hydrolysis reaction prior to the polymerization. The anchored catalyst was subsequently used to conduct the Ziegler–Natta polymerization reaction of ethylene. The modified fibers were incorporated into the polyethylene resin to produce composites at fiber concentrations as high as 15 wt%. The morphology of the fibers and the composites was tested using electron microscopy. Finally, the mechanical properties of the composites (in impact and tensile tests) were measured to characterize the properties of model composites. Polym. Compos. 27:129–137, 2006. © 2006 Society of Plastics Engineers.     

The effect of multiscale hybridization on the mechanical properties of natural fiber-reinforced composites

The main objective of this work was to investigate the effect of reinforcements at different scales on the mechanical properties of natural fiber-reinforced composites. Pure jute and interlaminar hybrid jute/glass fiber-reinforced polymer composites were fabricated. Different types of fillers in two weight fractions (1 and 3 wt. %) were used as second reinforcements in the hybrid jute/glass composites. Tensile, flexural, and impact tests were performed. It was found that the macroscale inter-play hybridization significantly improved the mechanical properties of the pure jute fiber based composites. When the fillers are used as second hybridization, the modified composites presented higher mechanical properties when compared to pure jute composites. However, the effect of fillers on the mechanical properties of the hybrid composites presented various trends due to the interaction between several factors (i.e., particle scale, content, and nature), which cannot always be separated. Increasing the synthetic filler content improved the tensile properties of the filled hybrid composites, while increasing the natural filler content worsen the tensile properties. The flexural strength of the multiscale hybrid composites was improved, while the impact properties were negatively affected.     

Physical,mechanical, and water absorption behavior of coir/glass fiber reinforced epoxy based hybrid composites

Fiber reinforced polymer composites has been used in a variety of application because of their many advantages such as relatively low cost of production, easy to fabricate, and superior strength compare to neat polymer resins. Reinforcement in polymer is either synthetic or natural. Synthetic fiber such as glass, carbon, etc. has high specific strength but their fields of application are limited due to higher cost of production. Recently there is an increase interest in natural composites which are made by reinforcement of natural fiber. In this connection, an investigation has been carried out to make better utilization of coconut coir fiber for making value added products. The objective of the present research work is to study the physical, mechanical, and water absorption behavior of coir/glass fiber reinforced epoxy based hybrid composites. The effect of fiber loading and length on mechanical properties like tensile strength, flexural strength, and hardness of composites is studied. The experimental results reveal that the maximum strength properties is observed for the composite with 10 wt% fiber loading at 15 mm length. The maximum flexural strength of 63 MPa is observed for composites with 10 wt% fiber loading at 15 mm fiber length. Similarly, the maximum hardness value of 21.3 Hv is obtained for composites with 10 wt% fiber loading at 20 mm fiber length. Also, the surface morphology of fractured surfaces after tensile testing is examined using scanning electron microscope (SEM). POLYM. COMPOS., 35:925–930, 2014. © 2013 Society of Plastics Engineers     

All-oxide ceramic matrix composites (OCMC) based on low cost 3M Nextel™ 610 fabrics

Cost reduction without loss of quality is a key factor during the development of engineering materials. This is particularly true for oxide fibers, which can represent up to 70 % of the real cost of all-oxide ceramic matrix composites (OCMC). Therefore, the objective of this work is to produce and evaluate OCMCs based on novel low-cost Nextel? 610 fiber fabrics with deniers of 3000?20,000. Experiments were divided into fiber and composite characterizations. In general, fiber bundles with higher denier show lower apparent strength; although fiber characteristic strength is very similar for bundles with denier below 4500. Composite characterization showed that certain properties, such as tensile strength, are in accordance to the measured fiber characteristic strength. Other properties like interlaminar shear strength and notch sensitivity did not depend on the type of fabric used. In summary, composites with the new fiber fabrics were successfully produced, showing properties similar to commercially available OCMCs.