JOINING BEHAVIOUR OF NATURAL FIBER REINFORCED THERMOSET AND THERMOPLASTIC COMPOSITES

Abstract

The usage of natural fiber based polymeric composites (NFRCs) is becoming quite popular in various non-structural and low load bearing applications. The NFRCs, being a class of sustainable materials, helps the research fraternity in achieving the goals of sustainable development by leading to environment friendly products. The various primary manufacturing processes such as injection moulding, extrusion, hand-layup and compression moulding have been extensively used to fabricate products with simpler profiles. However, the fabrication of products with complicated geometries requires understanding of the assembling/joining behvaiour of the materials. Thus, the secondary manufacturing processes; such as, machining and joining become inevitable to fabricate the products with complicated profiles. The joining of natural fiber composites is mostly done by stitching, mechanical fastening (using screws and nuts or bolts, rivets, clamps etc.), adhesives bonding and fusion bonding techniques. In the present experimental investigation, the joint strength of natural fiber (banana and bagasse) reinforced polymer composites at different fiber loading (10, 15 and 20%) was investigated. Further, comparative studies on the strength of joints employing molded and drilled hole for the purpose of fastening were carried out. The complete research investigation was carried out in three phases; In first phase, NFRCs were fabricated by using banana and bagasse fiber as reinforcement and epoxy as matrix material. Hand lay-up process was used for fabrication of composite laminates. Further, mechanical and thermal behavior of banana and bagasse fiber reinforced epoxy composites in terms of tensile and flexural strength and degradation of polymer and their composites with respect to temperature were carried out. The morphological analysis of failed samples during tensile testing were done to investigate the effect of reinforcement in matrix material. After that, joining behavior was investigated for polymers and their composites for three different types of joint configurations using adhesive bonding technique. During the second phase, NFRCs were faricated by using banana and bagasse as reinforcement and Polypropylene as matrix material. Extrusion Injection Molding (EIM) process was used for fabrication of composite specimens. Further, mechanical and thermal behavior of banana and bagasse fiber reinforced PP composites in terms of tensile and flexural strength and degradation of polymer and their composites with respect to temperature were experimentally investigated. After that, the morphological analysis of sample failed during tensile testing were carried out to determine the failure mechanism during loading conditions. Joining behavior of pure PP and its composites (at three different fiber loading) with fusion bonding technique (ultrasonic welding) was experimentally investigated. In third phase, comparative analysis of joints fabricated using molded and drilled hole in NFRCs adherends was performed. The joint strength achieved was characterized and compared using open hole, filled hole and bearing test were investigated. NFRCs were fabricated using hand lay-up process. Epoxy and polyester were used as matrix material and jute fiber (in woven form) were used as reinforcement. The analysis provided understanding of different modes of failure encountered in joints with molded and drilled hole specimens during open hole, filled hole and bearing test.