studied. None of the mechanical properties, excluding the fracture energies show signs of a positive hybrid effect (Marom et al., 1978). Manders and Bader (1981) reported hybrid effect and failure strain enhancement of up to 50% for the glass fiber/carbonfiber/epoxy composite. The failure strain of the carbon phase increased as the relative proportion of carbonfiber was decreases and as the carbon fibers were more finely dispersed. Yerramalli and Waas (2003) have considered carbon/ glass hybrid composite with an overall fiber volume fraction of 30%. Splitting and kinking failures were noted while loading the hybrid laminates under static and dynamic loading rates. Zhang et al. (2012) studied the mechanical behavior of hybrid composites made of carbon/glass reinforcements and the processing method used is ‘wet lay-up’ which is not a best practice for obtaining high quality laminates. An addition of hard reinforcements such as silicon carbide, alumina and titanium carbide improves hardness, strength and wear resistance of the composites (Amar Patnaik et al., 2009; and Chauhan et al., 2009). The introduction of a glass fiber into a polymer matrix produces a composite material that results in an attractive combination of physical and mechanical properties which cannot be obtained with monolithic alloys (Schwartz, 1984). Among the various useful polymer matrices, vinyl ester is typically characterized by properties such as fluidity, corrosion resistance and high strength-weight ratio (Suresha et al., 2007). The advantages of Fiber-reinforced PMCs over traditional materials include greater mechanical strength, lighter weight, better dimensional stability, higher dielectric strength and corrosion resistance and flexibility to improve the
For example, the mechanical properties of titanium based metal matrix composites reinforced by pyrocarbon coated SiC ﬁbers have been investigated by Carrere et al., 10) it was found that all the investigated coatings oﬀer rather good fatigue performance no matter what diﬀerences in morphol- ogy. As to the damping, it is well known that the poor interfacial bonding has a better damping capacity at the expense of strength as compared with the strong interfacial bonding, so adjusting the interface attribution of composites by means of introducing coating is a potential method to obtain the high damping. Unfortunately, there is little previous analytical and experimental work reported on the eﬀect of ﬁber coatings on the damping capacity of MMCs.
Meanwhile, carbon ﬁbers reinforced magnesium compo- sites have been recognized as new promising structural materials, due to their high speciﬁc strength and stiﬀness, high electrical and thermal conductivities. The main problem of fabricating these materials is that the molten magnesium does not wet or bond to carbon ﬁbers. As a result, it is diﬃcult to achieve eﬃcient load transfer from the matrix to the ﬁbers in accordance with the rule of mixture (ROM). There have been many developments proposed to solve this problem, including coating of titanium-boron by chemical vapor deposition (CVD) on carbon ﬁbers 7) or coating of silicon dioxide on carbon ﬁbers. 8,9) Katzman 9) successfully fabri-
pellet, GE plastics Co., Ltd.) was used for the matrix. The schematic diagram shown in Fig. 1 is the fabrication process of the titanium nickel ﬁber reinforced polycarbonate compo- site. We produced four kinds of specimens which were diﬀerentiated by their prestrain in the embedded titanium nickel ﬁbers as 0, 1, 3 and 5%. In order to produce the specimen, the titanium nickel ﬁbers (3 ﬁbers) were ﬁxed by a tensile prestrain device. Then, the ﬁbers were put between the polycarbonate pellets. After that, the pressure and temper- ature on the specimen were gradually changed, as shown in Figs. 2 and 3. After the molding device was taken out of the hot press, the specimen in the molding device was cooled down to room temperature naturally. The titanium nickel ﬁber was separated from the tensile prestrain device and the specimen was extracted from a shaping die.
FRP composite materials consist of fibres embedded in or bonded to a matrix with distinct interfaces between them. In this form, both fibres and matrix retain their physical and chemical identities, but they produce a combination of properties that cannot be achieved with either of the constituents acting alone. In general, fibres are the principal load carrying members, while the surrounding matrix keeps them in the desired location and orientation, acts as a load transfer medium between them, and protects them from environmental effects. Commercially, the principal fibres come in various types of glass and carbon as well as aramid. Other fibres, such as boron, silicate carbide and aluminium oxide, are in limited usage. All fibres can be incorporated into a matrix either in continuous lengths or in discontinuous (chopped) lengths. A polymer used as a matrix, is defined as a long chain molecule containing one or more repeating units of atoms, joined together by strong covalent bonds. Polymers are divided into two broad categories: thermoplastics and thermosets. Among the thermoset polymeric materials, epoxies and polyesters are widely used, mainly because of the ease of processing. EXPERIMENTAL PROGRAMME Numerous research works has been done on beams strengthened using FRP
The challenge in attempting to mitigate carbonfiber reinforced polymer degradation due to galvanic coupling to metals can be appreciated from Figure 2 showing the cathodic branch of the potentiodynamic polarization curve of carbonfiber reinforced polymer vis-a-vis the usual ranges of corrosion potentials for selected metals in aqueous media. It can be observed that for iron, its corrosion potential lies in the charge transfer controlled region of the polarization curve of CFRP. Consequently, on coupling iron to CFRP though the cathodic polarization on the carbonfiber reinforced polymer can be less severe because of lower oxygen reduction current densities. Secondly, the potential range to which CFRP is polarized being close to the potential for the 2-electron oxygen reduction reaction that produces the deleterious peroxide species (Equations (1), (6), and (7)) matrix degradation might be a possibility even at this seemingly benign cathodic polarization [ 278 ]. For the extreme case of magnesium coupled to CFRP, it can be observed that the CFRP will be polarized to potentials well beyond the potential ranges in which cathodic activity on it is under oxygen diffusion control and hydrogen reduction can already start. Even in the intermediate cases of galvanic coupling to zinc and aluminum in which the CFRP is polarized to potential ranges that cathodic processes on its surface are under diffusion control, the measured cathodic current densities in these potential ranges are quite significant, and reported to be in the range of ≈ 40 µA cm −2 in quiescent near-neutral chloride aqueous chloride media, and estimated to be capable of supporting anodic dissolution rates of about 0.599, 0.436, and 0.132 mm yr −1 for zinc, aluminum, and iron respectively, assuming equal cathodic and anodic surface areas [ 278 ]. Since the electrochemically active carbon phase in the CFRP is not metallic, diminution of electrochemical active surface area by interaction with organic
Carbon fibers possess high strength, wear resistance and excellent lubricity. Due to these reasons, they have been extensively used as reinforcements in discontinuous forms to develop MMC’s [7-9].However, carbon fibers exhibit high reactivity with light materials, especially with aluminium and its alloys, which limits its applications . Electroless nickel followed by copper electroplating has been identified as the promising solutions to overcome the above limitations [11-12]. It is reported that these metallic coatings improve the wetting behavior of carbon fibers with aluminium, leading to improved uniform distribution of carbonfiber reinforcement, reduced interfacial reaction and higher toughness of the composites [7, 8].These days, to develop light weight structures, carbon fibers in the form of bundles are used. The use of carbonfiber rod reinforced MMC’s in mining, chemical and marine environment has not gained much importance. This may be due to the fact that materials in these environments need to combat slurry type of erosion wear due to hard particles in liquid medium. Caron et al.  have studied the erosion wear behavior of Al5083-Al 2 O 3 composites and have noticed that slurry erosion wear of the composites
Fiber-reinforced polymer composite materials have become materials of choice for manufacturing application due to their high specific stiffness, strength and fatigue life, low density and thermal expansion coefficient. However, there are some types of defects such as porosity that form during the manufacturing processes of composites and alter their mechanical beha- vior and material properties. In his study, hand lay-up was conducted to fa- bricate samples of carbonfiber-reinforced polymer composites with three dif- ferent vacuum levels in order to vary porosity content. Nondestructive evalua- tion, destructive techniques and mechanical testing were conducted. Nonde- structive evaluation results showed the trend in percentages of porosity through-thickness. Serial sectioning images revealed significant details about the composite’s internal structure such as the volume, morphology and dis- tribution of porosity. Mechanical testing results showed that porosity led to a decrease in both Mode I static interlaminar fracture toughness and Mode I cyclic strain energy release rate fatigue life. The fractographic micrographs showed that porosity content increased as the vacuum decreased, and it drew a relationship between fracture mechanisms and mechanical properties of the composite under different modes of loading as a result of the porosity effects. Finally, in order to accurately quantify porosity percentages included in the samples of different vacuum levels, a comparison was made between the pa- rameters and percentages resulted from the nondestructive evaluation and mechanical testing and the features resulted from fractography and serial sec- tioning.
Silicon carbide nanofibers grew on the surface of carbon fibers of a unidirectional carbon preform by CCVD and then chemical vapor infiltration was used to densify the preform to get the SiCNF-C/C composite. The effects of silicon carbide nanofi- bers on the microstructure of the pyrolytic carbon and the thermal conductivity of the SiCNF-C/C composite were investigated. Results show that silicon carbide nano- fibers on the surface of carbon fibers induce the deposition of high texture pyrolytic carbon around them. The interface bonding between carbon fibers and pyrolytic carbon is well adjusted. So the efficiency of heat transfer in the interface of the com- posite is well enhanced. The thermal conductivity of the SiCNF-C/C composite is greater than that of the C/C composite, especially the thermal conductivity perpen- dicular to the fiber axis.
Machining-induced damage is commonly observed when manufacturing components based on carbonfiber reinforced polymer (CFRP) composites. Despite the importance of thermal effects in machining CFRPs, this problem has been poorly analyzed in the literature. Predictive tools are not available for thermal phenomena involved during cutting, while only few experimental studies have been found. In this paper, a three-dimensional (3D) finite element model of orthog- onal machining of CFRPs including thermal effects is presented. Predicted thermal and mechanical intralaminar damage showed strong influence of fiber orientation. Thermally affected area was larger than mechanically damaged zone. This fact confirms the importance of accounting for thermal effects when modelling CFRP machining.
The addition of electrically conductive fibers improves the conductivity of a concrete mixture. Steel and carbon fibers are electrically conductive, which help improve the conductivity of cementitious materials [7,16]. CNT and CNF based composites can serve as strain sensors . The piezioresistivity of conductive fiber-reinforced cementitious composite (FRC) materials changes with strain. The strain-sensing ability is caused by the change in the volume electrical resistivity of the concrete under dynamic or static loading. This is attributed to the fiber pull-out caused by increased straining of the material . Carbon fibers have been used to improve the mechanical and electrical properties of concrete , especially, to increase flexural strength, flexural toughness, and reduce drying shrinkage. Carbon nanofibers uniformly dispersed in a concrete matrix allow for the bridging of microcracks, which makes otherwise insulated space electrically conductive .
A positive or negative hybrid effect is defined as a positive or negative deviation of a certain mechanical property from the rule of hybrid mixture. The term hybrid effect has been used to describe the phenomenon of an apparent synergistic improvement in the properties of a composite containing two or more types of fibre. The selection of the components that make up the hybrid composite is determined by the purpose of hybridization, requirements imposed on the material or the construction being designed. The problem of selecting the type of compatible fibres and the level of their properties is of prime importance when designing and producing hybrid composites. The successful use of hybrid composites is determined by the chemical, mechanical and physical stability of the fibre / matrix system. There are several types of hybrid composites characterized as: (1) interply or towby-tow, in which tows of the two or more constituent types of fiber are mixed in a regular or random manner; (2) sandwich hybrids, also known as core-shell, in which one material is sandwiched between two layers of another; (3) interply or laminated, where alternate layers of the two (or more) materials are stacked in a regular manner; (4) intimately mixed hybrids, where the constituent fibers are made to mix as randomly as possible so that no over- concentration of any one type is present in the material; (5) other kinds, such as those reinforced with ribs, pultruded wires, thin veils of fiber or combinations of the above. The concept of hybrid systems for improved material or structural performance is well-known in engineering design. However, it is the inspiration from natures’ own materials that is recently motivating the path towards innovative material and structural designs. Studies on natural materials show how high structural performance can be achieved with non-exotic materials through hybrid combinations assembled in optimized hybrid hierarchical configurations. Although hybrid fiber reinforced polymer composites are gaining interest, the challenge is to replace conventional glass reinforced plastics with biocomposites that exhibit structural and functional stability during storage and use and yet are susceptible to environmental degradation upon disposal. An interesting approach in fabricating biocomposites of superior and desired properties include efficient and cost effective chemical modification of fibre, judicious selection if fibers, matrix modification by functionalizing and blending and efficient processing techniques. Another interesting concept is that of
relative densities of VGCF/Al composites and monolithic Al block were above 98.5% in this study. Figure 2 shows the optical and scanning electron microscopy (SEM) micro- graphs of the composites with average Al particle diameters of 1 mm, 3 mm and 30 mm, respectively. The dispersion of VGCF in VGCF dispersed Al matrix composites fabricated from 1 mm Al powders (VGCF/1 mm Al composite) is shown in Fig. 2(a). The gray and black regions are Al and C in Fig. 2(a), respectively. Figure 2(b) shows the enlargement of Fig. 2(a). VGCFs are dispersed uniformly in Al matrix as shown in Fig. 2(a). Whereas, the VGCFs were aggregated between Al particles mainly in the VGCF/30 mm Al composite as shown in Fig. 2(d) and (e). Moreover, the aggregation of VGCFs were arrayed along with special direction, because VGCF aggregation located at Al grain boundaries was deformed by two axial pressing during hot- pressing. On the other hand, the area of uniform dispersion of VGCFs, and the area of the agglomerated VGCFs are observed in the VGCF/3 mm Al composite as shown in Fig. 2(c). This shows the large contact grain boundary area between VGCF and Al could make uniform distribution of VGCFs in Al matrix. 17)
All fabrication processes used aluminum alloy metal powder as main constituent, must be mixed with the reinforcement homogeneously and can be classified as solid state. The basic steps consist of mixing of reinforcement particles with aluminum alloy pow- der by mechanical millings such as SPEX milling (Figure 1.7 ) or planetary high speed milling which followed consolidation by compaction and sintering to form a rigid part. Mechanical alloying, spark plasma sintering, mixing-hot pressing are some of the meth- ods which utilized for solid state fabrication of aluminum alloy matrix composite by powder metallurgy technique. Baker et al. have been reported a lot of broken fibres in carbon-aluminium composites produced by powder metallurgy and it was revealed a relatively weak interfaces bonding [ Baker, Braddick and Jackson , 1972 ]. The weak interfacial adherence acts as easy rout which has been demonstrated the propagation of fatigue cracks.
BirenJ.SaradavaEvaluation Of Mechanical And Water Absorption Behaviour Of Coir And Rice Husk Reinforced Composites  Hareesh M Mechanical Characterization Of Hybrid Hemp/Glass Fiber Reinforced Epoxy Composite, Mechanical EnggDepartmenT4BETP Mechanical Engg, International Journal Of Engineering Research And Reviews ISSN 2348-697X (Online) Vol. 4, Issue 1, Pp: (104-108),
composites with 3 mm carbon fibers prepared by microwave irradiation and conventional heating at 120˚C, and represents that the mechanical properties of pre-cured carbonfiber/epoxy resin composite which was cured for 1440 min at room temperature. In the case of the pre-cured carbonfiber/epoxy resin composite, the flexural modulus (Figure 1(a)) was 3.1 GPa. The flexural modulus of carbonfiber/epoxy resin composites cured by mi- crowave and conventional heating processing increased with increasing curing time. In the case of carbon fi- ber/epoxy resin composites irradiated by microwave for 5, 10 and 20 min, the flexural modulus was 3.9, 3.8, and 4.9 GPa, respectively. By microwave irradiation to pre-cured carbonfiber/epoxy resin composite for 20 min, the modulus increased rapidly. The flexural modulus of the microwave-irradiated carbonfiber/epoxy resin compos- ite for 20 min was higher in 60% than one of the pre-cured carbonfiber/epoxy resin composite. On the other hand, the flexural modulus of carbonfiber/epoxy resin composite prepared by conventional heating for 20 min was 3.3 GPa, indicating similar to one of the pre-cured carbonfiber/epoxy resin composite. Thus, the reaction between epoxy resin and curing agent was not accelerated at short time of conventional heating. When the cur- ing time of conventional heating was 180 min, the flexural modulus was 5.0 GPa. The value was similar to one of microwave-cured carbonfiber/epoxy resin composite for 20 min at 120˚C. Flexural strength and specific stiffness (Figures 1(b) and Figures 1(c)) showed the same tendency with flexural modulus (Figure 1(a)), indi- cating that microwave irradiation could rapidly cure epoxy resin in carbonfiber/epoxy resin composite as com- pared to conventional heating.
calized matrix or fiber architecture changes can meet local mechanical, electrical, or thermal loads within a component or vehicle, without the penalty of extra weight or the necessity to resort to additional external structures. Such integral materials reduce the number of components leading to not only more elegant designs, but also to structures that are less costly to manufacture. Local strength, stiffness, toughness, and thermal properties can be tailored by using carbon fibers and/or improved matrices. Numerous attempts have been made to increase the thermal conductivity of the matrix by adding high thermal conductivity solid fillers . Zhou surveyed the effect of coupling agents on the thermal conductivity of epoxy resin loaded with Al-particles . Lee et al. stu- died aluminum-nitride loaded epoxy resin . He et al . and Gu et al . utilized boron ni- tride nanoparticles in epoxy composites  . Hong et al . enhanced the thermal con- ductivity of epoxy composites with aluminum nitride and boron nitride fillers . Ma et al. investigated carbonfiber epoxy resin composites filled with silicon carbide par- ticles . Kusunose et al. used nanofibers instead of particles to improve the thermal conductivity of epoxy resin . Carbon nanotubes have frequently been used to in- crease thermal conductivities of resins. King et al. and Ma are cited exemplarily  . A very contemporary approach consists of using graphene nanoplatelets to achieve this goal  . However, to improve the thermal conductivity of the adhe- sives by a factor between 5 and 15, the above-mentioned fillers have to have a high enough load fraction, which would greatly affect their physical properties -. Especially the increase in viscosity above a threshold approximately 1 Pa·s prohibits the use of such resins for vacuum resin transfer molding . Thus, Liang et al. used a vo- lume fraction of only 0.1% of carbon nanofibers to increase the thermal conductivity of a carbonfiber composite plate in through-thickness direction produced by VARTM . The 10% increase in thermal conductivity can only be regarded as marginal.
Abstract: Due to the demands of personal travels and entertainments, light airplanes and small business aircrafts are developing rapidly. Light airplane structure is simple; however, it lacks crashworthiness design, especially the considerations on the impact of energy absorption. Therefore, in an event of accident, significant damage to passengers will be usually incurred. Airplanes made of composite materials structurally have high specific strength and good aerodynamic configuration. These materials have become the primary choice for new airplane development. This study mainly explores the topology optimization analysis of the light aircraft’s cockpit made of carbonfiber reinforced composites. This paper compares the compression amounts in the original models of composite material and aluminum alloy fuselages with the models after optimization during the crash-landing, in order to investigate the safety of fuselages made of different materials after structural optimization under the dynamic crashing. This study found that the energy absorbed by the aluminum alloy fuselage during crash-landing is still higher than that by the carbonfiber reinforced composites fuselage. On the other hand, the aluminum alloy fuselage after topology optimization could have an energy absorption capability enhanced by 40%, as compared to the that of the original model of aluminum alloy fuselage.
Frictional materials used in automobile brake linings are multifarious composite materials, and they are well-known as: i) High-steel (semi-metallic) brake pads containing 30% - 65% metal, ii) Low-steel (low-metallic) brake pads containing 10% - 30% metal, iii) Organic brake pads (also known as “non-asbestos organic” (NAO)) and iv) Hybrid brake pads, being a compromise between materials from group’s ii and iii. High-steel and low-steel friction materials possess several dis- advantages such as tendency to corrosion, low thermal stability, uneven wear of brake disk, etc., have restricted their braking applications. Modern friction ma- terials familiarly known as non-asbestos organic (NAO) made of thermoset composites have been utilized extensively, starting from bicycles, light commer- cial vehicles, heavy vehicles, airplanes, etc.   . These friction materials are a mixture of several ingredients, which includes many fillers, lubricants, fric- tion modifiers and reinforcing fibers bonded together by a thermosetting resin    . Of several kinds of reinforcing fibers as support in polymer ma- trix composites, fibers made of glass, carbon, aramid and so on are broadly used. They are categorized by their aspect ratio. Polymers are further can be streng- thened with different fillers that are accessible normally or synthesized in many forms such as, flakes, platelets, particles and so on to enhance their processabili- ty, mechanical, tribological and other performance, and in addition to reduce material cost. Filler particles of nano size with optimum loading percent have yielded the outstanding and synergistic performance in several characterization process. Many researchers have carried out the research on friction materials and the details of their research works has been discussed in Table 1.
Composite material is a combination of two or more materials, whose properties are superior to those of the constituent materials acting independently. Fiber- reinforced polymer composites are usually manufactured by embedding stiff and strong fibers into a relatively less stiff and compliant, polymeric matrix. The primary role of the fibers is to provide strength and stiffness to the composite . Typical reinforcing fibers used are glass, carbon and aramid, with fiber diameters in the range of 6-14μm. The role of the matrix material i.e. Epoxy resin is to hold the fibers in their position, protect the fibers from abrasion and the external environment (such as chemicals or moisture) and transfer load between fibers. Matrix material for polymeric composites can be either thermosets or thermoplastics . Thermoset resins usually consist of a low-molecular weight resin system and a compatible curing agent (also called a hardener). When the resin and hardener are mixed they form a low viscosity liquid that undergoes a chemical reaction to form three- dimensional cross-linked structures, resulting in an insoluble solid phase that cannot be reprocessed on reheating.