Hybrid Composite

INTRODUCTION A composite can be defined as a structural material consisting two or more combined constituents that are combined at a macroscopic level and are not soluble in each other (Kaw, 2006). One constituent is called the reinforcing phase and the one in which it is embedded is called the matrix. The reinforcing phase material may be in the form of fibres, whiskers, particles, or flakes. The matrix phase materials are generally continuous. Examples of composite systems include concrete reinforced with steel and epoxy reinforced with graphite fibres, etc. Normally, the components can be physically identified and exhibit an interface between one another. Usually, a traditional high performance composite is made by one single type of reinforcement (usually carbon fibre) and polymer matrix, which exhibits high specific strength and stiffness, long fatigue life and high chemical resistance. However, the ductility of this traditional composite is much lower compared with metals. Combining different types of fibres into a polymer matrix to manufacture hybrid composite can significantly improve the ductility of composites. The possible reason for this is that fibre with higher strength acts as a bridge between broken fibres of lower strain to failure. A lot of researchers have studied the mechanical performance of hybrid composites which commonly consist of different fibre yarns or laminae of different materials, but a relatively small amount of research reported in the literature has focused on intimately intermingled hybrid fibre composites, which can achieve a higher failure strain than traditional approaches. Furthermore, compared with carbon fibre /glass fibre hybrids, carbon fibre/carbon fibre hybrids will maintain high mechanical performance as single carbon composite but potentially its ductility could be improved by carefully design of the hybrid configuration. In this project, different carbon fibres will be used as reinforcement with a ductile thermoplastic matrix to manufacture intimately intermingled hybrid composites to achieve a higher ductility than that exhibited conventional single-fibre type composites. This optimised hybrid should have improved failure strain but maintain its high stiffness and strength compared with single carbon fibre-reinforced composites. This will potentially provide a model for novel high performance composite fibre approaches. So, there is a huge scope to investigate on optimum lamination parameters like choice of base material, different types of fabric materials, different types of binders, number of layers and laying angles. This work has focused on these areas of investigation.

A BRIEF REVIEW OF THE WORK ALREADY DONE IN THE FIELD: Acharya and Samantarai (2012) investigated the tribo potential of biomass based carbon black filler in epoxy composite. They observed that incorporation of Rice Husk Char in to epoxy significantly reduce abrasive wear loss. Ndazi et al. (2007) studied chemical and physical modifications of rice husk for use as composites panels. They found that chemical modification of rice husks by NaOH improves the adhesion properties of rice husk in composites due to removal of surface impurities such as silica and carboxylic compounds, which blocks reactive chemical groups. Studies are also available on aluminium reinforced by silicon carbide from rice husk. The reports based on these studies says that the reinforced aluminium not only has a good combination of room temperature specific strength and modulus and excellent thermal stability, but it also can be processed by normal metal working technique. Such materials are increasingly considered for aerospace applications where high stiffness and strength to weight ratios are additional advantages. The applications of Rice Husk Ash (RHA) as a filler in plastics is relatively limited mainly due to polypropylene (PP). As reported for a PP composites 30, with an increase in the RHA loading, its flexural modulus and density increases, where as its tensile strength, breaking elongation and impact strength decreases, yet RHA still can replace some commercial fillers. Navinchand et al. (1987) reported the studies on polyester filled with RHA. They have mentioned in their study reports that both the tensile and impact strength of the resulting composites were decreased with the increase in filler loading. they have also reported that in addition to being used in rubbers or plastics, RHA can also be used as a filler in rubber/plastic blends. Rozman H. D. et al. (2000) had made their studies on the effect of chemical modification of rice husk. They found and reported that with chemical modification in the rice husk, the reinforcing effect can be increased to an acceptable limit.

Silvia Luciana Favaro et al. (2010) studied the chemical, morphological and mechanical analysis of rice husk/post-consumer polyethylene (PE) composites. PE and rice husk were chemically modified to improve their compatibility in composite preparation. They found improved fibre surface adhesion with matrix and improved mechanical performance compared to pure polymer matrix, on the other hand no benefit is observed in the tensile strength over the pure PE. Garcia et al. (2007) used a combination of waste tire rubber and rice husk with different size particles as raw materials in their research for obtaining new materials by sintering technique so that environmental problems could be reduced. Ayswarya et al. (2012) studied the use of RHA for property modification on high density polyethylene (HDPE). They found and reported that RHA is a valuable reinforcing material for HDPE and the environmental pollution arising due to RHA can also be eliminated. Rout and Satpathy (2012) studied mechanical and tribo-performance of rice-husk filled glass-epoxy hybrid composites. They found that hardness, tensile modulus and impact energy of these new class hybrid composites are enhanced with the rice husk as filler additive whereas a steady decline of tensile and flexural properties are also observed. Bohlooli et al. (2012) analytically investigated the compressive strength of geopolymers with seeded fly ash and rice husk bark ash by fuzzy logic modelling. They found that fuzzy logic can be an alternative approach for evaluating the effect of seeded mixture of fly ash and rice husk bark ash on compressive strength values of geopolymer specimens. Kwon et al. (2013) investigated the flexural properties and dimensional stability of the sandwich-structured composites comprising the rice husk particles in the core layer and randomly aligned the wood strands in the face layers. They found that 10–40% of the strands into the face layers of the RH particleboards improved the flexural modulus and strength. Ahmad et al. (2012)were performed their research on using of rice husk powder as reinforcing filler in blends of natural rubber(NR) and high density polyethylene. They

observed that the incorporation of radiated Rice Husk into NR/HDPE blends improved the mechanical properties tensile stress and modulus and impact strength and hardness. Mahboobeh Azadi et al. (2011) investigated the influence of the RHA on different mechanical properties of the cured coatings (wear, hardness, and elongation). The presence of RHA in epoxy paints can enhance wear resistance, scratch resistance, and elongation. It seems that this type of filler in epoxy paints increases paint plasticity. The addition of white ash is better in improving the wear resistance due to the presence of more silica. Adding 20 wt% black ash to the pure epoxy paint lowers its friction coefficient with respect to the white RHA. Finally, using this type of filler, which is cheap and abundant in nature, can modify some mechanical properties of epoxy paints and also reduce air pollution from burning rice husks. Thus, a ‘green product’ can be produced in the paint industry. S. Mahzan et al. uses natural fibre for studying sound absorption properties. This study investigates the use of rice-husk waste as the potential element for sound absorption material of rice-husk reinforced composite. The study of rice husk waste material for sound absorption purposes has been reported. The optimum percentage of rice husk was obtained at 25%. The pattern obtained for rice husk was similar to membrane absorber curves which are predominant at the lower frequencies. Furthermore the peaks α value was obtained at 250Hz. Comparison between virgin Polyurethane (PU) and the optimum percentage of rice husk (25%) indicated that α value of mixture is higher than virgin PU at low frequency whereas for high frequency the virgin PU is higher. The comparison between other natural materials also has been done for recycled rubber and wood shavings. The result demonstrates that rice husk is superior to both materials for range 0-500Hz. Since, rice husk is available in large amount, the potential for commercialization, especially for low frequency sound absorbent material is possible. Reis et al. (2011) studied experimentally the effect of cork and rice husk ash micro particles fillers on the mechanical properties (flexural resistance, fracture toughness, impact absorbed energy, elastic and viscous moduli) of polyester based hand moulded composite was. Filled materials exhibit fragile behaviour and flexure strength much lower than polyester matrix, and decreasing significantly when the filler content increases from 1 to 5%. The resistance loss is more pronounced for cork powder than for rice husk ash filler. Fracture toughness is also much lower for the filled composites than for the polymer

matrix. Using cork powder the fracture toughness decreases significantly with filler content, while for rice husk ash filler a slight increase was observed. Both fillers improve absorbed impact energy, peaking about 2.5% on filler content. Better improvements were obtained using rice husk ash powder, reaching about 30%. Both fillers increase glass transition temperature and the maximum use temperature and also the elastic modulus compared with observed for the polyester, reaching the modulus a peak for 2.5% of filler content. Yussuf et al. (2010) investigated and compared the performances of polylactic acid (PLA)/kenaf (PLA-K) and PLA/rice husk (PLA-RH) composites in terms of biodegradability, mechanical and thermal properties. It was found that flexural modulus of pure PLA was increased drastically when filled with both kenaf and rice husk fibres; however, the flexural and impact strengths declined. For composites, it was found that kenaf composite shows better mechanical properties compare to rice husk composite. The thermal stability of the virgin PLA was decreased by addition of kenaf and rice husk; and the composite with rice husk fibre showed higher thermal degradation than kenaf composite. From the results of biodegradability, it was found that addition of natural fibres slightly improves biodegradability of PLA and kenaf has more significant effect on the biodegradation rate, which exhibits better performances than rice husk. Stefani et al. (2005) proposed the use of rice husk as filler for increasing the value of recycled tire rubber. They observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed. Sisir Mantry et al. (2011) fabricated a jute-epoxy composites with reinforcement of SiC derived from rice husk. They reported that incorporation of fillers modifies the tensile, flexural and inter-laminar shear strength of the jute epoxy composites. They also investigated that the presence of particulate fillers (silicon carbide) in these composites improves their erosion wear resistance. Y. Arao, S. Yumitori, H. Suzuki, T. Tanaka, K. Tanaka and T. Katayama did a remarkable work on Mechanical properties of injection-molded carbon fiber/polypropylene composites hybridized with nanofillers in the year of 2013. In this work the mechanical properties of CF/PP hybridized with nanofillers were investigated. The strength of the

composites increased with the incorporation of MAPP because of the improvement in the adhesion properties between fiber and matrix. It has been shown that addition of a small amount of a nanofiller can improve not only the strength of the composite but also the elastic modulus. Alumina, silica, and CNT have positive effects on the strength of the composite, while the addition of clay decreases the mechanical properties. The results of fiber pull-out tests and the observation of fracture surfaces indicated that the nanofillers (alumina, silica, and CNT) improve the IFSS of the composite. In the same year 2013, Samuel Rivallant, Christophe Bouvet and Natthawat Hongkarnjanaku did a work on Failure analysis of CFRP laminates subjected to compression after impact. Their work presented a model for the numerical simulation of impact damage, permanent indentation and compression after impact (CAI) in CFRP laminates. The same model was used for the formation of damage developing during both low-velocity/low-energy impact tests and CAI tests. The different impact and CAI elementary damage types were taken into account, i.e. matrix cracking, fiber failure and interface delamination. Experimental tests and model results were compared, and that comparison was used to highlight the laminate failure scenario during residual compression tests. Finally, the impact energy effect on the residual strength was evaluated and compared to experimental results. Ying Zhang, Jie Shen, Qing Li, Long Pang, Quanyuan Zhang, Zushun Xu, Kelvin W.K. Yeung and Changfeng Yi did a research in 2013 on Synthesis and characterization of novel hyperbranched polyimides/attapulgite nanocomposites. In this work Novel hyperbranched polyimides/attapulgite (HBPI/AT) nanocomposites were successfully synthesized by in situ polymerization. HBPI derived from novel 2,4,6-tri[3-(4aminophenoxy)phenyl]pyridine dicarboxyphenoxy)phenyl]propane

(TAPP)

and

2,2-bis[4-(3,4-

dianhydride

(BPADA).

4,40-diphenylmethane

diisocyanate (MDI) modified AT copolymerized with HBPI and the nanocomposites formed multilinked network. Chemical structure, morphology, thermal behavior, and mechanical properties of nanocomposites were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile testing et.al. Results indicated that modified AT was homogeneously dispersed in matrix and resulted in an improvement

of thermal stability, mechanical properties and water resistance of HBPI/AT nanocomposites. Another work was done in the year 2013 by M. Saleem, L. Toubal, R. Zitoune and H. Bougherara on the effect of machining processes on the mechanical behavior of composite plates with circular holes. The aim of this work was to examine the influence of two machining processes namely conventional machining (CM) and abrasive water jet machining (AWJM) on the mechanical behavior of composite plates under cyclic loading. For this purpose, an experimental study using several composite plates drilled with a cutting tool and an abrasive water jet machining was carried out. In order to study the impact of the process of machining on the mechanical behavior, thermographic infrared testing and fatigue cyclic tests were performed to assess temperature evolutions, stiffness degradation, and the damage evolution in these plates. Fatigue testing results have shown that the damage accumulation in specimens drilled with CM process was higher than the AWJM specimens. Furthermore, the endurance limit for a composite plate drilled with CM was approximately 10% inferior compared to specimens drilled with AWJM. This difference can be related to the initial surface integrity after machining induced by the difference in the mechanism of material’s removal between the two processes used.