Thermoplastic composite induction welder

Abstract

Induction heating of thermoplastic composite materials is accomplished to form a continuous bonded joint. A zone of optimum heating can be created by an induction heating coil mounted within and adjacent to the drum of a hollow circular roller of non-conductive material (i.e., transparent to the RF field) so that an induction heating field can be created and localized to create a zone of optimum heating at the joint area of the material to be bonded. Simultaneously pressure to that area can be applied by the circular roller. In a preferred form, the roller is semi-rigid to permit spreading of the contact surface with the joint area to avoid absolute contact line loading. A hand held induction heating unit with a finger operable power switch can be moved in a back and forth manner over the joint to apply heat when the switch is turned on and effect consolidation when the switch is turned off. Using the techniques of the invention, one can fuse two contacting members which are comprised of filamentary reinforced composite materials in which the matrix resin at the joint interface is a member of the thermoplastic family of polymers. The invention concentrates radio frequency (RF) energy at the joint interface which heats the surrounding layers and simultaneously provides for the application of a controlled force normal to the mid-plane of the joint to retain compaction of the laminates which would normally be relieved in a hot unrestrained condition.