Synthesis and characterization of short Grewia optiva fiber‐based polymer composites

Natural fibers, such as Flax, Sisal, Hibiscus Sabdariffa, and Grewia optiva (GO) possess good reinforcing capability when properly compounded with polymers. These fibers are relatively inexpensive, easily available from renewable resources, and possess favorable values of specific strength and specific modulus. The mechanical performance of natural fiber‐reinforced polymers (FRPs) is often limited owing to a weak fiber‐ matrix interface. In contrast, urea–formaldehyde (UF) resins are well known to have a strong adhesion to most cellulose‐containing materials. This article deals with the synthesis of short G. optiva fiber‐reinforced UF polymer matrix‐based composites. G. optiva fiber‐reinforced UF composites processed by compression molding have been studied by evaluating their mechanical, physical, and chemical properties. This work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength, and wear resistance of the UF matrix increase up to 30% fiber loading and then decreases for higher loading when fibers are incorporated into the polymer matrix. Morphological and thermal studies of the matrix, fiber, and short FRP composites have also been carried out. The swelling, moisture absorbance, chemical resistance, and water uptake behavior of these composites have also been carried out at different intervals. The results obtained lay emphasis on the utilization of these fibers, as potential reinforcing materials in bio‐based polymer composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Analysis of mechanical properties and free vibrational characteristics of novel Grewia optiva/basalt fiber reinforced hybrid polymer composites

This study emphasize on the fabrication and testing of Grewia optiva/Basalt fiber reinforced polymer composites for use in internal applications of automobiles and aircraft. The study investigates the use of Grewia optiva fiber (local plant based fiber) with Basalt fiber, where chopped Basalt fiber (6, 9, and 12 mm) is reinforced in polyester matrix in combination with Grewia optiva fiber. Composite test specimen are fabricated and analyzed using a smart actuation system to evaluate the free vibrational behavior of the composites experimentally. The impact of various parameters including length of the fiber and its weight percentage on the free vibrational behavior of composites is determined. The percentage of individual reinforced fiber is varied (0, 4, 8, and 12 wt.%) maintaining fiber weight % constant, that is, 12 wt.% of composite. The experimental results help to identify the variations in natural frequencies of Basalt/Grewia optiva fiber based composites. B12/GO0 demonstrate the natural frequency of 67 Hz and 44.71 MPa tensile strength for 12 mm fiber reinforced composites. The finding from this experimental work provide insights into the potential applications of Basalt/Grewia optiva fiber reinforced composites for automobile and air craft industries.     

Synthesis and Characterization of Grewia Optiva Fiber-reinforced PF-based Composites

In this article, the synthesis of natural fiber-reinforced phenol-formaldehyde (PF) resin matrix-based polymer composites has been reported. Initially the phenol-formaldehyde resin was prepared by varying the concentration of formaldehyde with a fixed weight of phenol. Polymeric resins of different P:F ratios were subjected for optimization of their mechanical properties. The sample ratio of 1:1.5 (P:F) was found to possess maximum mechanical strength. Then reinforcing of this optimized resin was done by taking different ratios of Grewia optiva fiber in particle form (200 μ) to prepare green polymer composites. The polymer composite materials thus prepared were subjected for evaluation of their mechanical properties such as tensile, compressive, flexural, and wear resistance. It has been observed that optimum mechanical properties were obtained for fiber loading of 30%. Further, the mechanical strength of the composites has been found to be higher than the parent phenol-formaldehyde resin matrix. The morphological and thermal properties of the composites have also been studied.     

Effect of alkali treatment on properties of unidirectional isora fibre reinforced epoxy composites

Abstract

Unidirectional isora fibre reinforced epoxy composites were prepared by compression moulding. Isora is a natural bast fibre separated from Helicteres isora plant by retting process. The effect of alkali treatment on the properties of the fibre was studied by scanning electron microscopy (SEM), IR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Mechanical properties such as tensile strength, Young's modulus, flexural strength, flexural modulus and impact strength of the composites containing untreated and alkali treated fibres have been studied as a function of fibre loading. The optimum fibre loading for tensile properties of the untreated fibre composite was found to be 49% by volume and for flexural properties the loading was optimised at ～45%. Impact strength of the composite increased with increase in fibre loading and remained constant at a fibre loading of 54·5%. Alkali treated fibre composite showed improved thermal and mechanical properties compared to untreated fibre composite. From dynamic mechanical analysis (DMA) studies it was observed that the alkali treated fibre composites have higher E' and low tan δ maximum values compared to untreated fibre composites. From swelling studies in methyl ethyl ketone it was observed that the mole percentage of uptake of the solvent by the treated fibre composites is less than that by the untreated fibre composites. From these results it can be concluded that in composites containing alkalised fibres there is enhanced interfacial adhesion between the fibre and the matrix leading to better properties, compared to untreated fibre composites.     

Curing Characteristics and Mechanical Properties of Oil Palm Wood Flour Reinforced Epoxidized Natural Rubber Composites

Abstract

The paper reports on the curing characteristics and mechanical properties of oil palm wood flour (OPWF) reinforced epoxidized natural rubber (ENR) composites. Three sizes of OPWF at different filler loadings were compounded with a two roll mill. The cure (t ₉₀) and scorch times of all filler size decrease with increasing OPWF loading. Increasing OPWF loading in ENR compound resulted in reduction of tensile strength and elongation at break but increased tensile modulus, tear strength and hardness. The composites filled with smaller OPWF size showed higher tensile strength, tensile modulus and tear strength. Scanning electron microscope (SEM) micrographs showed that at lower filler loading the fracture of composites occurred mainly due to the breakage of fibre with minimum pull-out of fibres from the matrix. However as the filler loading is increased, the fibre pull-out became very prominent due to the lack of adhesion between fibre and rubber matrix.     

Chemical Resistance,Mechanical and Physical Properties of Biofibers-Based Polymer Composites

A study on physical and chemical properties along with mechanical characterization of Hibiscus Sabdariffa fiber-reinforced Phenol–Formaldehyde resin matrix based polymer composites have been reported. Effect of fiber dimension on mechanical properties was evaluated. The interfacial bonding between Hibiscus Sabdariffa fiber and polymer matrix has been found to affect the properties of polymer matrix. It has been observed that particle reinforced polymer composites exhibit better mechanical properties as compared to short and long fiber reinforced polymeric composites. These composites were further subjected to evaluation of morphological, thermal, physical (swelling and moisture absorption) and chemical properties.     

Effects of fibre type and matrix structure on the mechanical performance of self-compacting micro-concrete composites

The compatibility of matrix and fibre properties is one of the key parameters in the successful design of fibre reinforced cementitious composites. In order to achieve the desired performance, the properties of each constituent of composite should be properly configured. The aim of this study was to investigate the performance of two polymer based micro-fibres (polypropylene and polyvinyl alcohol) in different matrices (high strength and comparatively low strength with fly ash incorporation) which were designed to contain considerably high amounts of fibres (1% by volume) while maintaining their self-compactability. The fresh state thixotropic behaviour of fibre reinforced matrices was minimised by proper adjustment of water/cementitious material ratio and admixture dosage. The mechanical properties (first crack strength and displacement, flexural strength and relative toughness) of prismatic composite samples were compared by three point flexural loading test. The typical behaviours of selected composites and collapse mechanisms of PP and PVA fibres in these matrices were characterised by microstructural studies. It was concluded that, a high strength matrix with a high strength fibre give the best performance from the view point of flexural strength and toughness performance. However, incorporation of fly ash did not cause a significant reduction in composite performance possibly due to its enhancing effect on matrix–fibre interface adhesion. The possibilities and suggestions to further improve the performance of the composites were also discussed.     

Polypropylene matrix composites reinforced with pre-stressed glass fibers

Thermoplastic matrix composites have recently emerged as promising engineering materials because of their desirable properties such as high service temperatures, high impact resistance, and processing advantages. However, residual stresses in composites introduced during fabrication are cited as one of the most significant problems in the processing of composites. In some instances these stresses have been shown to significantly degrade the strength of the material, resulting in matrix cracking, debonding, reduced fracture toughness, and delamination. In this work, studies have been carried out on glass fiber reinforced polypropylene composites formed by compression molding process from co-mingled fabrics. The fibers were pre-stressed during the process to produce high performance composite products with low residual microstresses, which are harmful to the properties of the composite. Mechanical tests showed that pre-stress can increase the tensile, flexural and interlaminar shear properties of the composites, and there exists an optimum pre-stress level to gain best properties for each external loading condition.     

Mechanical characterization and modeling of poly (β‐hydroxybutyrate)‐co‐poly(β‐hydroxyvalerate)–Alfa fiber‐reinforced composites

The mechanical properties of biobased composites of poly(β‐hydroxybutyrate)‐co‐poly(β‐hydroxyvalerate) biopolymer continuously reinforced with unidirectional Alfa fibers are investigated via tensile testing of oriented composite laminates. Simple mechanical models for the elastic stiffness, strength, and nonlinear hardening of the biobased composites are proposed with an emphasis on techniques that only require the independent properties of the fiber and matrix to facilitate composite design. Rule of mixtures (ROM) approaches are found to effectively predict the elastic properties of the composites but generally overestimate strength. Modified ROM approaches that discount the contribution of the matrix in the fiber loading direction and the contribution of the fiber in the transverse loading direction provide the most accurate strength predictions. Apparent elastic properties for composites with varying fiber orientations are predicted using a modified orthotropic laminate plate method which was found to overestimate composite stiffness in off‐axis loading directions. Postyield nonlinear hardening is modeled using a calibrated continuum yield and plasticity model and demonstrated to provide a close match of the experimental results. POLYM. COMPOS., 35:1758–1766, 2014. © 2014 Society of Plastics Engineers     

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     

Effect of fiber loading and orientation on mechanical and erosion wear behaviors of glass–epoxy composites

For a composite material, its mechanical behavior and surface damage by solid particle erosion depend on many factors. One of the most important factors is the fiber content. Similarly, these properties are also greatly affected by the fiber orientation. In this work, a series of experiments were carried out to investigate the influence of fiber loading and fiber orientation on mechanical and erosion behavior of glass fiber‐reinforced epoxy composites. The composites were fabricated with three different fiber loadings (20, 30, and 40 wt%) and at four different fiber orientations (15°, 30°, 45°, and 60°). The conclusions drawn on the basis of the experimental findings are discussed, and composite with 30° fiber orientation shows better microhardness compared with other fiber orientations irrespective of fiber loading. Similar observations are also noticed for other mechanical properties of the composites, such as tensile strength, flexural strength, interlaminar shear strength, impact strength, etc. Finally, the morphology of eroded surfaces is examined using scanning electron microscopy (SEM), and possible erosion mechanisms are identified. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Biodegradable Composites: Ramie Fibre Reinforced PLLA-PCL Composite Prepared by in Situ Polymerization Process

Summary  Thermoplastic biodegradable composites based on ramie fibre (RF) and a poly(l-lactic acid)-poly(ε-caprolactone) (PLLA-PCL) matrix was manufactured using the in situ polymerization method. In order to improve the compatibility and strengthen the interface in natural fibre composite materials, the RF was firstly treated by coupling agents. Then the RF reinforced thermoplastic PLLA-PCL composite was prepared by in situ polymerization of PLLA oligomer with NCO-terminated PCL prepolymer. The effect of fibre length and fibre content on tensile strength and impact strength of this natural-fibre-reinforced biodegradable composite (PLLA-PCL/RF) was discussed, including the influence of the use of silane coupling agent (KH550) for improved interfacial adhesion. The results showed that the tensile strength and impact strength of PLLA-PCL/RF were highest when the RF length was 5-6mm, RF content was 45% and with KH550 as surface treatment agent of RF.     

Microstructure and properties of CNTs reinforced CVI-pyrocarbon matrix

Pyrocarbon (PyC) matrices were prepared in two kinds of quartz fiber preforms by chemical vapor infiltration (CVI), and then the fibers were leached by HF. Effects of CNTs on the microstructures and mechanical properties of the quartz fiber reinforced carbon composites and PyC matrices, as well as the interface behaviors of the fiber reinforced composites, were discussed. Randomly oriented CNTs reinforced PyC micro-composites account for the pseudo ISO structure and contribute to the mechanical properties of the PyC matrix. Relative strength between reinforcement and matrix and interface bonding significantly affect the mechanical behaviors of the quartz fiber reinforced pyrocarbon composites: Quartz fiber with low strength and strong interface bonding result in limited strengthening effect on flexural strength of the fiber reinforced composite; low strength unidirectional quartz fiber and weak interface bonding in a much stronger matrix result in limited strengthening effect on tensile strength of the composite.     

POLYSTYRENE-BENZOYLATED EFB REINFORCED COMPOSITES

Reinforced thermoplastics generally are produced by incorporation of reinforcement agents or fillers into thermoplastic resins. The utilization of lignocellulosic material as filler with reinforcement in polymer matrix has received much interest due to its lower price and other properties. A composite of polystyrene reinforced with oil palm empty fruit bunches (EFB) and chemically treated EFB with benzoyl chloride (EFB-benzoylated) as a function of loading and fiber surface modification were prepared. The chemically treated fibers were analyzed with FT-IR to observe the extent of chemical reaction with EFB fiber. The sharp peak at 710 cm^?1 appeared on the spectra, which indicated that the mono-substituted benzene ring has taken place. The strong peak at 1720 cm^?1 has indicated the presence of ester group treated fiber. The flexural test was performed using Instron 4301 testing machine to study flexural properties of the composites with various fiber sizes. The results showed that the flexural properties increased with particle size. The flexural strength of EFB-benzoylated composites was observed to be stronger than untreated EFB fiber. Scanning electron microscope was used to investigate the morphological structure of the fiber surface, fiber pull out, fracture surface, and fiber–matrix interface. The untreated EFB composites showed hole and fiber end, which indicated that most of the fiber have pulled out breaking during the fracture of composites; however, the treated EFB-benzoylated showed a good adhesion between fiber and matrix.     

A Comparative Study on the Mechanical Properties of Jute and Sisal Fiber Reinforced Polymer Composites

The aim of the present study is to investigate and compare the mechanical properties of raw jute and sisal fiber reinforced epoxy composites with sodium hydroxide treated jute and sisal fiber reinforced epoxy composites. This is followed by comparisons of the sodium hydroxide treated jute and sisal fiber reinforced composites. The jute and sisal fibers were treated with 20% sodium hydroxide for 2 h and then incorporated into the epoxy matrix by a molding technique to form the composites. Similar techniques have been adopted for the fabrication of raw jute and sisal fiber reinforced epoxy composites. The raw jute and sisal fiber reinforced epoxy composites and the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites were characterized by FTIR. The mechanical properties (tensile and flexural strength), water absorption and morphological changes were investigated for the composite samples. It was found that the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites exhibited better mechanical properties than the raw jute and raw sisal fiber reinforced composites. When comparing the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites, the sodium hydroxide treated jute fiber reinforced composites exhibited better mechanical properties than the latter.     

Carbon/carbon composites based on a polyimide matrix with coal tar pitch

Blending of coal tar pitch with a polyimide precursor based on acetyl derivatives of aromatic diamines during its synthesis leads to a homogeneous, highly thermostable matrix for carbon fibre reinforced composites. If the weight content of the pitch in the polyimide matrix does not exceed 40%, the mechanical properties (flexural strength, shear modulus and fracture toughness) of these composites are comparable to those of similar composites based on a pure polyimide matrix. Carbonisation and graphitisation of the composites with a properly blended matrix precursor leads to carbon fibre reinforced carbon composites with lower open porosity and higher density, elastic modulus and flexural strength than those of composites based on a pure polyimide matrix.     

Sisal fibers treated with NaOH and benzophenonetetracarboxylic dianhydride as reinforcement of phenolic matrix

In this work, composites based on a phenolic matrix and untreated‐ and treated sisal fibers were prepared. The treated sisal fibers used were those reacted with NaOH 2% solution and esterified using benzophenonetetracarboxylic dianhydride (BTDA). These treated fibers were modified with the objective of improving the adhesion of the fiber–matrix interface, which in turn influences the properties of the composites. BTDA was chosen as the esterifying agent to take advantage of the possibility of introducing the polar and aromatic groups that are also present in the matrix structure into the surface of the fiber, which could then intensify the interactions occurring in the fiber–matrix interface. The fibers were then analyzed by SEM and FTIR to ascertain their chemical composition. The results showed that the fibers had been successfully modified. The composites (reinforced with 15%, w/w of 3.0 cm length sisal fiber randomly distributed) were characterized by SEM, impact strength, and water absorption capacity. In the tests conducted, the response of the composites was affected both by properties of the matrix and the fibers, besides the interfacial properties of the fiber–matrix. Overall, the results showed that the fiber treatment resulted in a composite that was less hygroscopic although with somewhat lower impact strength, when compared with the composite reinforced with untreated sisal fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of stress transfer between fiber and matrix on toughness of polymer composite

Thanks to their lightweight properties, formability and low cost, polymers have become an essential material for manufactured products. To improve the mechanical properties, almost all polymers are blended with some kind of fiber made from glass, carbon, organic or natural material. The importance of interfacial strength between matrix and fiber is a well known requirement for effective mechanical properties and some experimental results indicate that low interfacial strength helps increase the toughness of composites. In this paper, models of composite reinforced by fiber aligned with maximum principal stress under uni‐tensile loading are simulated. Based on the simulation result, we discuss the effect of interfacial strength, aspect ratio of fiber and friction force between matrix and fiber on stable deformation and provide the guidelines for establishing composites with high modulus and toughness. POLYM. COMPOS. 2011. © 2011 Society of Plastics Engineers     

Thermal Aging Properties of Graphite Fiber Reinforced Peek and Graphite Fiber Reinforced Bmi Composites

Graphite fiber reinforced poly(ether ether ketone) (PEEK) and graphite fiber reinforced bismaleimide (BMI) composite materials are two kinds of advanced fiber-reinforced polymer matrix composites with good thermal stability and excellent mechanical properties at high temperature. They are currently receiving considerable attention. the main limitation on their application is the lack of knowledge regarding their behaviors during extended use at high temperature. Thermal aging properties are the main parameters for new polymer matrix composites that will be used in advanced spacecraft structural components. From the results of thermal aging effects on the properties—including interlaminar shear strength, drop-weight impact strength, and impact energy—of graphite/PEEK and graphite/BMI composites, it is found that unidirectional graphite fiber reinforced composites retain higher strength compared to multidirectional, and that multidirectional graphite/PEEK composites keep higher property retentions than multidirectional graphite/BMI composites after thermal aging at 190°C. From scanning electron photomicrographs, it is also found that graphite/PEEK composites have better fiber/resin adhesion, intraply adhesion, and microcrack resistance compared to graphite/BMI composites after thermal aging.