CHARACTERIZATION AND MACHINABLITY STUDY OF NATURAL FIBER REINFORCED COMPOSITES

Abstract

The natural fiber reinforced composites are being used as a sustainable alternative to wood and synthetic fiber reinforced composites in many engineering applications, such as, in automotive and packaging industry. This has been propelled by the global concern for the environment as well as the use of non-renewable resources and the subsequent hunt for eco-friendly materials. In particular, the concern has led to new and stringent environmental policies forcing the automotive, packaging and construction industries to look out for substitute reinforcements for traditional composite materials having a plastic matrix. Synthetic fibers have serious limitations, including their higher initial processing costs, non-recyclability, higher energy consumption, and non-biodegradability among others. Moreover, the other unaddressed and compliance issues from new environmental legislations and consumers (like global warming) and stringent needs of manufacturing industries, especially; packaging, construction and automotive industries, has motivated researchers to explore and investigate the scope of renewable materials to possibly replace existing conventional and non-renewable reinforcing materials, such as glass fibers. Thus, the drawbacks of the syntheticfiber reinforcedpolymer composites and the increasing global energy crisis in recent years have drawn attention towards natural fibers as reinforcement materials. As a result, there is a global trend towards the use of plant fibers (hemp, kenaf, sisal, jute, coir and flax. etc.) as reinforcements and fillers for polymer composites. It is noteworthy that generally; natural fibers rarely match the strength of traditional advanced fibers, especially as the modulus of the cellulose crystal is equivalent to that for aramid fiber and less than that for carbon fiber. However, plant-based fiber-reinforced composites can replace non-load bearing household plastic products. They can also be used in the manufacture of automotive and building materials, where the load-bearing capacity and dimensional stability under moist conditions are of secondary importance. These days more and more natural fibers are being employed as reinforcement in thermoplastic and thermoset resin matrices, as they are favoured for their excellent chemical resistance, and good noise damping properties. The breakthrough of natural fibers as reinforcement materials has become inevitable in the field of composites materials. Natural fiber based composites can be tailored for various applications by maintaining a proper selection of fibers, matrix, additives and manufacturing process. In comparison with the use of fiber-glass reinforced components, the natural fibers potentially decrease the component weight by 10%, in addition to decrease in energy requirement during production process iv (80%). As a result, the cost of the component reduces by 5%.Currently, dominant thermoplastic matrices are polypropylene (PP), polyethylene (PE), and poly vinyl chloride (PVC). Of these, polypropylene (PP) is most extensively used, due to its strength, high wear resistance with low-cost and good performance, and its ease of process ability. In the present research investigation, partially biodegradable composites based on polypropylene with three different types of plain-woven natural fibers namely, hemp, jute and sisalwere developed using compression moulding technique. The developed composites were characterized for their mechanical properties, environmental behaviour,tribological behaviour and secondary processing (drilling operation). Mechanical properties (tensile and flexural strength) were evaluated using standard test procedures. The morphology of the failed surface was analysed by scanning electron microscopy.Environmental behaviour of the developed composites upon exposure to various environmental conditions has been investigated by measuring the weight change and the tensile strength after exposing the specimens for 12 weeks (3 months).The dry sliding wear behaviour of the developed composites was evaluated in terms of coefficient of friction and specific wear rate using pin-on-disc rotating type friction and wear tribometer for different sliding conditions (applied load, sliding speed and sliding distance). Wear performance of the developed composites was found toimprove significantly due to the addition of natural fibers. Drilling behaviour of the developed composites was experimentally investigated with drilling forces(thrust force and torque) and drilling induced damage as the output responses. The cutting speed, feed rate and the drill point geometry being the input process parameters. Three solid carbide drill point geometries have been used namely, Twist drill, Jo drill and, Parabolic drill. The drill tool geometry was found to be an important criteria, which affects the drilling forces and subsequently the delamination. The drilling induced damage has been quantified using the stereo-optical microscope setup. The current experimental endeavour has established the importance of natural fibers as a viable alternative for synthetic fibers. The overall results indicate that the natural fiber reinforced PP composites have a strong potential in many engineering application such as furniture and packaging industry.