Advanced Materials Research Vols. 984-985

Abstract: Composites find lot of applications in aerospace, defence, automotive and medical industries due to its high strength to stiffness and weight ratio. After the composites are demoulded, trimming the edges is the first machining operation to be carried out. The heterogeneity and anisotropy of the composite materials make machining difficult and accompanied with different damages. The accuracy of the surface profile is one of the important components of both dimensional and geometric accuracy and play a significant role in achieving overall product quality because it is often directly related to the product’s functional performance. The defects in the free edges are mainly influenced by the machining parameters (such as speed, feed, depth of cut and fibre orientation) and the type of machining (orthogonal cutting and oblique cutting). This paper presents some observations like feed force, normal force and surface roughness made on the orthogonal and oblique cutting of unidirectional carbon fiber reinforced plastics.

Abstract: The natural fiber reinforced polymer composites are recognized as an alternative to wood and plastics in recent years. The natural plant fibers are extracted from various parts of the tree and are used in polymer composites.The present investigation is focused on the improvement of tensile strength of coir-vinyl ester composites by impregnation of bio particulates such as alumina, red mud and rice husk. The fracture method of composite specimens are analyzed with the help of scanning electron micrographs.The observed range of tensile strength values are studied using statistical procedure and non linear regression models are developed.

Abstract: Stir casting is an economical method to produce aluminum matrix composites (AMCs). In the present work, Aluminum alloy AA6061 reinforced with various amounts (0, 5, 10 and 15wt. %) of SiC particles were prepared. The matrix alloy was melted in a furnace and stirred to form a vortex. SiC particles were added to the periphery of the vortex and the composite melt was solidified in a permanent mold. The microstructures of the AMCs were studied using optical and scanning electron microscopy. SiC particles were observed to refine the grains and were distributed homogeneously in the aluminum matrix. SiC particle clusters were also seen in a few places. SiC particles were properly bonded to the aluminum matrix. Dry sliding wear behavior was analyzed by Pin on Disc apparatus. The reinforcement of SiC particles improved the wear resistance of the AMCs.The details of worn surface and wear debris are also presented in this paper.

Abstract: Wire Electrical discharge Machining plays an important role in the field of hard, difficult to machine materials like metal matrix composites. Machining process must keep pace with material development. For electrically conductive materials wire electro discharge machining is a viable option due to high accuracy, precision, and ability to achieve complex, intricate shaped profiles on even thin works. Due to thermo-electric nature it is a stochastic process in nature. To simplify the difficulty in determining parameters for the improvement of cutting performance and optimization, analysis of variance and regression analysis were made use of. Tungsten carbide cobalt metal matrix composites finds increasing applications in conventional application like tools and dies as well as in developing fields like bio-medical instruments and aero-space industries. In this present work, the problem of parameter selection, optimization for wire electro discharge machining on tungsten carbide-15% cobalt metal matrix composites, a less worked composition has been undertaken. Sodick AQ-427L wire-edm machine was used with a 0.25 diameter zinc coated brass wire electrode, to cut the material. Each experiment done under different cutting conditions of inputs like pulse on time, pulse off time, wire speed and peak current and repeated for three observations and the average was selected. Optimum machining parameter combination for material removal rate was obtained by using the desirability response optimizer function. Analysis of variance, Confirmation experiment was carried and good improvements were obtained.

Abstract: AA2024-T4 Al substrate with and without bonded E-glass/Epoxy patches were undergone for the experimental study of tensile strength and fatigue behavior. The Al substrates were machined to edge cracked specimens. The strength of the substrate was decreased due to the presence of crack when compared with un-cracked Al substrate. The patches were made in liquid epoxy resin instead of film adhesives and it was discovered that the both static strength and fatigue life were significantly increased for bonded composite patches. Different ply patches were applied on the cracked Al substrates and it was noted that the 9ply patch demonstrated its effectiveness in preventing static failure and increasing fatigue life of the cracked substrates

Abstract: Whiskers usually have strength equal to that of a perfect crystal. They have been found very useful as reinforcement for metal matrix composites. They enhance mechanical properties, thermal stability, wear resistance, and also make them as light weighted ones. Aluminum borate (9Al₂O₃.2B₂O₃) is an effective replacement to silicon carbide whiskers in its use as reinforcement in aluminum metal owing to its high tensile strength, oxidation resistance, chemical stability and wear resistance. In this work, aluminum borate whisker preparation is carried out by sol-gel process using aluminum nitrate and boric acid. The prepared whiskers are then characterized for its morphological and phase properties by SEM and XRD respectively. The study shows that 3% NiO added sample fired at 1100^oC with 2 hours soaking had better aspect ratio and productivity.

Abstract: Nickel as a ferromagnetic material has better damping characteristics and as a result, it can absorb more acoustic energy. Compared to existing ferromagnetic shape memory alloy, nickel is cheaper and might have similar damping characteristics. It has better corrosion resistant and heat resistant than other metals. In this study polymer matrix composite consisting polyester with metal (Nickel) particle reinforcement is considered. Polymer matrix is reinforced with the Nickel particle to improve its mechanical and damping properties. Different volume fraction of matrix and reinforcement are taken into consideration. Change in mechanical properties as a function of variable reinforcement has been analyzed in detail. Acoustic energy absorption of composite will be analyzed in the future.

Abstract: Natural fibers are used for replacing synthetic fibers as reinforcement in various matrices. This paper is presents the fabrication and water absorption characteristics of various natural fibers reinforced composite fabricated by hand layering technique. The water absorbing capacity, diffusion and permeability of various natural fibers like rice straw, Kenaf, Coconut Spathe, Coconut Guinit reinforced composite with different dipping time intervals were analyzed. Morphological analysis was carried out on fabricated and soaked samples using scanning electron microscope. From the experimental work it is observed that coconut guinits and rice straw shows comparatively very low water absorbing capacity. Alkaline treatment of fibers doesnot have any major variation in water absorbing capacity.

Abstract: Due to the light weight, high strength to weight ratio, corrosion resistance and other advantages, natural fibre based composites are becoming important composite materials in mechanical engineering fields. The current project emphasizes the newly identified Pandanus Fibre (Pandanus Fascicularis) which is extracted from the stem of screw pine tree by the manual water treatment process. The mechanical properties of chopped Pandanus fibre by Polyester composites are investigated and compared with the similar natural fibres in the fibre reinforced composite material field. The composite plates were fabricated with raw pandanus fibres by compression moulding method with varying weight percentage and lengths of fibre.

Abstract: Woven fabric composites are now being increasingly used in aircraft and automobile structures due to balanced properties in the fabric plane. In the present work, woven fabric glass beam is modified and strengthened by interplying high modulus carbon fabric plies for improving the strength to weight ratio and thereby to achieve better performance in various dynamic conditions. The objective of the present work is to investigate the vibration behavior of cantilever type glass/carbon hybrid composite beams subjected to higher frequency of operation using finite element method. Unit plied woven fabric glass, carbon and hybrid of glass/carbon laminates were fabricated using hand layup technique. Experimental modal analysis of unit plied composite beams was carried out by impulse excitation technique under fixed free boundary condition. Theoretical modal analysis was done by finite element method using elastic constants derived from rule of mixture equations. The experimental and theoretical frequency results were compared and analyzed for finding the degree of deviation using regression analysis. The coefficients of regression analysis were used to find effective elastic constants of composite laminates. Further these effective elastic constants were applied for modal analysis of hybrid composite beams under higher frequency range. The results of mode shape, modal frequency of hybrid beams were reported and discussed. The effect of stacking sequence and effect of beam size on vibration characteristics at higher frequency range was also discussed.