MICROWAVE JOINING OF THERMOPLASTIC BASED NATURAL FIBER COMPOSITES

Abstract

The use of Polymer Matrix Composites (PMCs) has increased considerably over the last decade. The PMCs have been widely used for manufacturing of aircraft and spacecraft structural parts because of their superior mechanical and physical properties such as high specific strength and stiffness. These composites are generally fabricated using high strength synthetic fibers such as carbon, glass and kevlar with thermoplastic resins (nylons and polyolefin), thennoset resins (epoxies, polyurethanes) and unsaturated polyesters. Because of environmental awareness and new rules and regulations laid down by the governments worldwide, sustainability and eco-efficiency has gained prime importance and now most of the work is focused on replacing synthetic fibers, like glass with fully bio-degradable environmentally friendly lignocellulosic natural fibers (Grewia optiva fibers (GOF), Nettle fibers (NF), sisal fibers (SF) etc.). Therefore, in the presentinvestigation; process has been developed for the manufacturing of thermoplastic based natural fiber composite laminates. Green and partially green composites have been developed successfully. Joining is widely used operation for composites. In the present work, the feasibility study of thermal joining using electromagnetic waves (microwaves) for fiber reinforced polymeric (FRP) composites viz, sisal fiber reinforced polylactic acid (PLA/SF(10% wt., 20% wt.)) and glass fiber reinforced epoxy resin (Epoxy/GF(4 Ply)) has been done. Microwave joining of composite laminates is a fast and energy efficient process. Process can be made even faster with the aid of materials which highly couple with microwave interactions e.g. charcoal. Fixed frequency facility, 2.45 GHz, has been used for the current investigation. After successful joining of PLA/SF green composite laminates with microwave energy, simulation of joining process has been carried out using COMSOL Multiphysics software tool. Bond strength of fully green (PLA/GOF and PLA/NF) and partially green (PP/GOF and PP/NF) composite laminates has been investigated and it has been found that the strength of microwave joined adherends is higher than adhesively bonded adherends.