Weldability and heat affected zone (HAZ) evaluation for high energy rate joining of thermoplastic composites using microwaves

Abstract

[Summary]: Industrial microwave technology for processing polymers and polymer based composites is currently in a state of considerable flux. This paper extends the applications horizon of microwaves in the area of reinforced thermoplastic composites joining, and places emphasis on the development of equipment and facilities aiming at maximising bond quality. It discusses the microwave facility used, including a 0.8 kW variable control power generator operating at 2.45 GHz, waveguide and a tuning piston designed for obtaining a standing wave at the seam of the butted and lapped test pieces. The effect of power input and cycle time on the heat affected zone is detailed together with the underlying principles of test piece material interactions with electromagnetic field. The process of autogenous joining of 33% by weight of random glass fibre reinforced nylon 66, polystyrene (PS) and low density polyethylene (LDPE) as well as 23.3 % by weight of carbon fibre reinforced PS thermoplastic composites is mentioned together with developments using filler materials, or primers in the heterogenous joining mode. The weldability dependence on the dielectric loss tangent of these materials is also described.