Mechanical behavior of composites reinforced with fibers caroa

Composites were prepared with 13, 23 30 and 40 % fiber and evaluated the mechanical performance in tensile, flexural and impact. The mechanical properties of these composites were also evaluated function of time at 110 °C thermal exposure. Caroa fibers were characterized by techniques such as thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the best mechanical properties were achieved for composites containing 23 to 30 % fiber. The incorporation of 23 % fiber caroa increased both the modulus of elasticity in the tensile test as the flexural strength and impact, the composite with 30 % fiber caroa showed higher tensile strength. The results show that the tensile and flexural strength of the composite decreased with time of thermal exposure. The thermal aging at 110 °C caused a decrease in tensile properties of the composites.     

Development of mathematical models and estimation for the mechanical properties of organic fiber reinforced polyester composites

Organic fiber from animal waste was used for the development of environmentally friendly animal fiber based polyester composites using cow hair. The cow hair fibers were cut into 10 mm lengths to produce the needed short fiber for random dispersion in the matrix. Before use, some of the fibers were treated with sodium hydroxide for fiber surface modification while some were left as untreated. Composites were developed using predetermined proportions of the fibers in an open mould production process. Samples were formed into tensile and flexural shape in their respective moulds and were stripped off the moulds after curing while further curing was ensured for 27 days before testing. Tensile and flexural properties of the cow hair fiber reinforced polyester composites were evaluated from which it was discovered that the untreated fiber reinforced composites possess better enhancement of mechanical properties compared to the treated fiber reinforced composites and the unreinforced polyester material. Mathematical models for the tensile and flexural properties were developed using statistical packages and estimation using developed software. The developed models revealed high degree of correlation between the experimental values and the predicted values. This denotes that the models can be used to predict the mechanical properties of cow hair reinforced polyester composites for various reinforcement contents.     

An experimental investigation on the response of woven natural silk fiber/epoxy sandwich composite panels under low velocity impact

This paper presents results of dynamic deformation behavior of woven natural silk/epoxy sandwich composite panels. The specimens were prepared in configurations of reinforced woven natural silk fiber (RWNSF)/Epoxy/Foam, RWNSF/Epoxy/Coremat; RWNSF/Epoxy/Honeycomb and reinforced RWNSF/Epoxy (control material) using hand-lay-up method. Each of the three core material was sandwiched between reinforced woven natural silk fiber/Epoxy composite facesheet. Drop weight impact test was carried out under 32 J impact energy. Degree of damages inflicted on the contact surface, through thickness and rear surface were analyzed, sandwich composites performed better than the reinforced (control material). Failure mechanism involved interlaminar matrix cracking, layer debonding, delamination and fibre breakage.     

Coir fiber reinforced polypropylene composite panel for automotive interior applications

In this study, physical, mechanical, and flammability properties of coconut fiber reinforced polypropylene (PP) composite panels were evaluated. Four levels of the coir fiber content (40, 50, 60, and 70 % based on the composition by weight) were mixed with the PP powder and a coupling agent, 3 wt % maleic anhydride grafted PP (MAPP) powder. The water resistance and the internal bond strength of the composites were negatively influenced by increasing coir fiber content. However, the flexural strength, the tensile strength, and the hardness of the composites improved with increasing the coir fiber content up to 60 wt %. The flame retardancy of the composites improved with increasing coir fiber content. The results suggest that an optimal composite panel formulation for automotive interior applications is a mixture of 60 wt % coir fiber, 37 wt % PP powder, and 3 wt % MAPP.     

Modeling and experimental validation of tensile properties of sugar palm fiber reinforced high impact polystyrene composites

Sugar palm fiber is one of the most abundant natural fibers used in biocomposites. However, prediction of the mechanical properties of such natural fiber reinforced composites is still challenging. Most of the theoretical modelings are based the micromechanical method. There have been little studies involving statistical approach for prediction of mechanical properties of natural fiber reinforced composites. In this study, the tensile properties of short sugar palm fiber-reinforced high impact polystyrene (SPF-HIPS) composites obtained by means of statistical approach were investigated and compared with the experimental observations and with micromechanical models available in the literature. Statistical approach was used to predict the performance of the composite part with different fiber loadings. A two-parameter Weibull distribution function was used to model the fiber length distribution in the composite. For the experimental validation, the composites were prepared by hot compression technique for different fiber loadings (10 %, 20 %, 30 %, 40 % and 50 % by weight). Tensile testing of the composites was carried out according to ASTM D638 to obtain the composites tensile strength and modulus of elasticity. Experimental results showed that the tensile strength of the composite reduced due to the addition of sugar palm fibers, whereas the elastic modulus increased by a factor of up to 1.34. The current statistical model predicted the tensile properties of SPF-HIPS composite close to the experimental values. It was found that statistical approach with standard micromechanical models can be used to predict the mechanical properties of sugar palm fiber reinforced HIPS composites. Hence, this study could assist in decisions regarding the design of natural fiber reinforced composite products.     

Experimental investigation of mechanical behavior of Jute-Flax based glass fiber reinforced composite

Present technological development and innovation needs a better class of material that meets all the practical applications along with its environmental friendly nature and economical value. Hybrid natural fiber composites, a sector of natural composites meets these requirements. This paper deals with fabrication, mechanical characterization of a hybrid (Jute+Flax+GFRP) composite and also the comparison of it with the (Jute+GFRP) based composite. These composites are fabricated using hand lay-up technique. The arrangement of hybrid composite is such that a layer of vertically laid flax fiber is flanked between layers of horizontally laid jute fiber. Epoxy resin alongside with HY951 hardener is used as the binding agent throughout the layer. Glass fiber laminates are used on both sides for improving the surface finish and surface hardness. The volumetric fraction is such that one third of total volume is occupied by Jute and Flax fibers. Test results shows that the hybrid natural composite has excellent properties under tensile, flexural loading. At last failure morphology analysis is done using Scanning Electron Microscope (SEM) and the internal structure of the broken specimen is discussed.     

Impact of succinic anhydride on the properties of jute fiber/polypropylene biocomposites

Chemical treatment is an often-followed route to improve the physical and mechanical properties of natural fiber reinforced polymer matrix composites. In this study, the effect of chemical treatment on physical and mechanical properties of jute fiber reinforced polypropylene (PP) biocomposites with different fiber loading (5, 10, 15, and 20 wt%) were investigated. Before being manufactured jute fiber/PP composite, raw jute fiber was chemically treated with succinic anhydride for the chemical reaction with cellulose hydroxyl group of fiber and to increase adhesion and compatibility to the polymer matrix. Jute fiber/PP composites were fabricated using high voltage hot compression technique. Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) tests were employed to evaluate the morphological properties of composite. Succinic anhydride underwent a chemical reaction with raw jute fiber which was confirmed through FTIR results. SEM micrographs of the fractured surface area were taken to study the fiber/matrix interface adhesion and compatibility. Reduced fiber agglomeration and improved interfacial bonding was observed under SEM in the case of treated jute fiber/PP composites. The mechanical properties of jute/PP composite in terms of Tensile strength and Young’s modulus was found to be increased with fiber loading up to 15 wt% and decreased at 20 wt%. Conversely, flexural strength and flexural modulus increased with fiber loading up to 10 wt% and start decreasing at 15 wt%. The treated jute/PP composite samples had higher hardness (Rockwell) and lower water absorption value compared to that of the untreated ones.     

Experimental study on structure and mechanical properties of hemp/PBTG composites with fiber contents and thermal exposures

Most materials used in daily life are polymeric materials based on petrochemistry. The used polymeric materials can cause land pollution and air pollution after landfill or incineration. In contrast, natural fiber reinforced (NFR) composites are more suitable for the environment, however the reliability in terms of the durability and weatherability of NFR composites is still lacking. Thus, NFR composites require the reliability involved with durability and weatherability. In this work, poly(butylene terephthalate-co-glutarate) (PBTG), with a chemical structure similar to biodegradable PBAT, was used as the matrix in the composites, and hemp fibers were used as the reinforcement. Hemp/PBTG composites were fabricated by stacking hemp-fiberwebs and PBTG films with various fiber contents and thermal exposure times. Characteristics of the composites, such as the morphological structure, chemical structure, tensile properties, compressive properties, flexural properties, and impact strength, were analyzed to obtain the effects of fiber volume fraction and thermal exposure. As a result, hemp/PBTG composites were hardened in proportion to fiber volume fractions, and the hardening behavior of the composites increased tensile strength and flexural strength. However, the hardened structure of the composites decreased the impact strength and compressive strength of the composites. On the other hand, the mechanical properties of hemp/PBTG composites with thermal exposure times, were governed significantly by the brittleness behavior of the resin and the increased crystallinity of hemp fibers. Thus, the hemp fibers contributed to the improvements on structural stability, tensile strength and flexural strength of the hemp/PBTG composites, and increased the thermal durability of the composites with various thermal exposures.     

Influence of wood species and particle size on mechanical and thermal properties of wood polypropylene composites

This study aims to investigate the effects of two types of wood flour; oil palm mesocarp flour (OMF) and rubberwood flour (RWF), and their particle sizes on mechanical, physical, and thermal properties of wood flour reinforced recycled polypropylene (rPP) composites. The composite materials were manufactured into panels by using a twin-screw extruder. The rPP composites based on RWF significantly showed higher flexural, tensile, and compressive properties (both strength and modulus) as well as hardness and thermal stability than those composites based on OMF for the same particle sizes. However, distribution of RWF in the rPP matrix was less homogeneous than that of the rPP/OMF composites. Furthermore, a decrease of the particle sizes of filler for the rPP/OMF or RWF composites increased the flexural, tensile, compressive, and hardness properties. Likewise, the thermal stability of both OMF and RWF composites were insignificantly affected by the particle sizes.     

Matrix modification with silane coupling agent for carbon fiber reinforced epoxy composites

To improve interfacial adhesion between carbon fiber and epoxy resin, the epoxy matrix is modified with N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (YDH602) and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (YDH792), respectively. And the effect of matrix modification on the mechanical performance of carbon/epoxy composites is investigated in terms of tensile, flexural and interlaminar properties. The flexural properties indicate that the optimum concentration of silane coupling agents YDH602 and YDH792 for the matrix modification is approximately 0.5 wt% of the epoxy resin system, and the mechanical properties of the YDH792-modified epoxy composites is better than that of the YDH602-modified epoxy composites at the same concentration. Compared to unmodified epoxy composite, the incorporation of 0.5 wt% YDH792 results in an increase of 4, 44 and 42 % in tensile, flexural and interlaminar shear strength (ILSS) values of the carbon/epoxy composite, respectively, while the corresponding enhancement of tensile and flexural modulus is 3 and 15 %. These improvements in mechanical properties can be considered to be an indication of better fiber/matrix interfacial adhesion as confirmed by SEM micrographs of the fracture surface after interlaminar shear testing. The viscosity of the modified epoxy resin system can be reduced by incorporation of silane coupling agent YDH792, which is beneficial for fiber impregnation or wetting during liquid composite molding process.     

Effect of reinforcement and chemical treatment of fiber on The Properties of jute-coir fiber reinforced hybrid polypropylene composites

Present research investigates the mechanical properties of jute-coir fiber reinforced hybrid polypropylene (PP) composite with fiber loading variation and observes the effect of chemical treatment of fiber on property enhancement of the composites. Composites were manufactured using hot press machine at four levels of fiber loading (5, 10, 15 and 20 wt%). Fiber ratio’s were varied (jute:coir=1:1, 3:1 and 1:3) for 20 % fiber loaded composites. Both jute and coir fiber was treated using 5 % and 10 % NaOH solutions. Composites were also prepared using treated fiber with jute-coir fiber ratio of 3:1. Tensile, flexural, impact and hardness tests and Fourier transform infrared spectroscopic analysis were conducted for characterization of the composites. Tensile test of composite showed a decreasing trend of tensile strength and increasing trend of the Young’s modulus with increase in fiber loading. During flexural, impact and hardness tests, the flexural strength, flexural modulus, impact strength and hardness values were found to be increased with increase in fiber loading. All these properties enhanced with the enhancement of jute content except impact strength. 5 % NaOH treatment provided an improving trend of properties whereas, 10 % NaOH treatment showed the reverse one. The FTIR analysis of the composites indicated decrease of hemicelluloses and lignin content with alkali treatment.     

Effect of the low and radio frequency oxygen plasma treatment of jute fiber on mechanical properties of jute fiber/polyester composite

We investigated the surface modification of jute fiber by oxygen plasma treatments. Jute fibers were treated in different plasma reactors (radio frequency “RF” and low frequency “LF” plasma reactors) using O₂ for different plasma powers to increase the interface adhesion between jute fiber and polyester matrix. The influence of various plasma reactors on mechanical properties of jute fiber-reinforced polyester composites was reported. Tensile, flexure, short beam shear tests were used to determine the mechanical properties of the composites. The interlaminar shear strength increased from 11.5 MPa for the untreated jute fiber/polyester composite to 19.8 and 26.3 MPa for LF and RF oxygen plasma treated jute fiber/polyester composites, respectively. O₂ plasma treatment also improved the tensile and flexural strengths of jute fiber/ polyester composites for both plasma systems. It is clear that O₂ plasma treatment of jute fibers by using RF plasma system instead of using LF plasma system brings about greater improvement on the mechanical properties of jute/polyester composites.     

Fabrication of long and discontinuous natural fiber reinforced polypropylene biocomposites and their mechanical properties

Natural fiber reinforced polypropylene (PP) biocomposites were fabricated by blending long-and-discontinuous (LD) natural fibers (NF) with LD PP fibers. Firstly, random fiber mats were prepared by mixing NFs and PP fibers using a carding process. Then, heat and pressure were applied to the mats, such that the PP fibers dispersed in the mats melted and flowed out, resulting in the formation of consolidated sheets upon subsequent cooling. The effect of the fiber volume fraction on the mechanical properties of the bio-composites was scrutinized by carrying out tensile and flexural tests and observing the interface between the fiber and matrix. It was observed that the natural LD fiber content needs to be maintained at less than the nominal fiber fraction of 40 % by weight for the composites fabricated using the current method, which is quite low compared to that of continuous or short fiber reinforced composites. The limited fiber fraction can be explained by the void content in the biocomposites, which may be caused by the non-uniform packing or the deficiency of the matrix PP fibers.     

Compatibilizing effects of polypropylene-g-itaconic acid on the polypropylene composites

We prepared long carbon fiber (LCF)-reinforced thermoplastic composites using a compatibilizer of itaconic acid grafted polypropylene (PP-g-IA). We confirmed the structure of PP-g-IA and investigated the compatibilizing effects of PPg- IA on LCF/polypropylene composites. The tensile strength, tensile moduli, flexural strength, and flexural moduli of the composites increased with increasing PP-g-IA content in the thermoplastic composites. Using single pull-out analyzing system, we found PP-g-IA improved interfacial strength between the carbon fiber and PP matrix. The thermal properties of the composites were measured by thermogravimetric analysis (TGA). We could observe that LCF enhanced the mechanical properties and thermal decomposition temperature of the polypropylene (PP) composites, compared with neat PP. The fractured surfaces of PP/PP-g-IA/LCF composites showed that PP-g-IA was effective for improving the interfacial adhesion between LCF and PP matrix.     

Mechanical properties of flax-g-poly(methyl acrylate) reinforced phenolic composites

In order to develop composites with better mechanical properties and environmental performance, it becomes necessary to increase the hydrophobicity of the natural fibers and to improve the interface between matrix and natural fibers. Graft copolymerization of natural fibers is one of the best methods to attain these improvements. Only few workers have reported the use of graft copolymers as reinforcing material in the preparation of composites. So in the present paper, we report the preparation of graft copolymers of flax fibers with methyl acrylate (MA) using Fenton’s reagent (FAS-H₂O₂) as redox system. Synthesized flax-g-poly(MA) was characterized with FTIR, TGA/DTA, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. Composites were prepared using flax-g-poly(MA) as a reinforcement and phenolformaldehyde (PF) as the binding material. Mechanical properties of phenol-formaldehyde composites were compared and it has been found that composites reinforced with flax-g-poly(MA) showed improvement in mechanical properties. Composites reinforced with flax-g-poly(MA) showed better tensile strength (235 N) and compressive strength (814 N) in comparison to composites reinforced with original flax fiber which showed lesser tensile strength (162 N) and compressive strength (372 N). Composites reinforced with flax-g-poly(MA) shows the improved MOR, MOE, and SP.     

Effect of fiber length on mechanical behavior of coir fiber reinforced epoxy composites

Fiber reinforced polymer composites have played a dominant role for a long time in a variety of applications for their high specific strength and modulus. The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. To this end, an investigation has been carried out to make use of coir, a natural fiber abundantly available in India. Natural fibers are not only strong and lightweight but also relatively very cheap. The present work describes the development and characterization of a new set of natural fiber based polymer composites consisting of coconut coir as reinforcement and epoxy resin as matrix material. The developed composites are characterized with respect to their mechanical characteristics. Experiments are carried out to study the effect of fiber length on mechanical behavior of these epoxy based polymer composites. Finally, the scanning electron microscope (SEM) of fractured surfaces has been done to study their surface morphology.     

Enhancement of the mechanical properties of glass/polyester composites via matrix modification glass/polyester composite siloxane matrix modification

Enhancement of the mechanical and vibrational properties of glass/polyester composites was aimed via matrix modification technique. To achieve this, unsaturated polyester was modified by incorporation of oligomeric siloxane in the concentration range of 1–3 wt%. Modified matrix composites reinforced with woven roving glass fabric were compared with untreated glass/polyester in terms of mechanical and interlaminar properties by conducting tensile, flexure, and short-beam shear tests. It was found that after incorporation of 3 % oligomeric siloxane into the polyester matrix, the tensile, flexural, and interlaminar shear strength (ILSS) values of the resulting composite increased by 16, 15, and 75 %, respectively. The increases in ILSS as well as in tensile and flexural properties were considered to be an indication of better fiber/matrix interaction as confirmed by SEM fractography images. Furthermore, the effect of oligomeric siloxane incorporation on the vibrational properties of the composites was investigated by experimental modal testing and the natural frequencies of the composites were found to increase with increasing siloxane concentration.     

Flexural characteristics of coir fiber reinforced cementitious composites

This study has examined the flexural properties of natural and chemically modified coir fiber reinforced cementitious composites (CFRCC). Coir fibers of two different average lengths were used, and the longer coir fibers were also treated with a 1 % NaOH solution for comparison. The fibers were combined with cementitious materials and chemical agents (dispersant, defoamer or wetting agent) to form CFRCC. The flexural properties of the composites, including elastic stress, flexural strength, toughness and toughness index, were measured. The effects of fiber treatments, addition of chemical agents and accelerated ageing of composites on the composites’ flexural properties were examined. The results showed that the CFRCC samples were 5–12 % lighter than the conventional mortar, and that the addition of coir fibers improved the flexural strength of the CFRCC materials. Toughness and toughness index, which were associated with the work of fracture, were increased more than ten times. For the alkalized long coir fiber composites, a higher immediate and long-term toughness index was achieved. SEM microstructure images revealed improved physicochemical bonding in the treated CFRCC.     

Mechanical and thermo-mechanical analysis based numerical simulation of granite powder filled polymer composites for wind turbine blade

In present article fabrication and characterization of unfilled and granite powder filled carbon epoxy composites are reported. Addition of carbon fiber shows positive effect on mechanical performance of the composites. However, incorporation of granite powder has negative hybridizing effect on the properties such as tensile strength, flexural strength and inter-laminar shear strength. The storage modulus evaluated at 30 °C is in close agreement with flexural modulus of composites. Further, successful attempt is made for numerical simulation of actual geometry of wind turbine blade. The results obtained from numerical analysis are comparable with experimental results.     

Reliability improvement of hemp based bio-composite by surface modification

The influence of the surface treatments on the performance of the hemp/PP (polypropylene) composite was investigated. The composites were prepared from the fiber modified by the alkalis and the oil under various conditions. The mechanical properties of the composites were measured using the tensile test, and the service time of the composite was assessed under accelerated condition by the stepped isothermal method. The alkaline treatment removed the lignin successfully and resulted in better fibrillation. The oil treatment improved the mechanical properties of the composites and extended the service life time of the composites.