A composite fibrous susceptor for use in induction welding is described, along with methods of its construction and use. The composite fibrous susceptor can include a magnetically susceptible continuous fiber in conjunction with a thermoplastic polymer. The composite fibrous susceptor can be deposited according to an additive manufacturing process on a surface to be bonded according to an induction welding process.

A method for welding thermoplastic composite parts while actively cooling includes placing a first composite part onto a surface of a tooling, placing a second composite part onto the first composite, pressing the second composite part toward the first composite part with an induction welding end effector, and providing a flow of air or gas through an opening extending through the shaping surface while induction welding the second composite part to the first composite part. The first composite is sandwiched between the surface of the tooling and the second composite. The flow of air or gas impinges on a bottom surface of the first composite part and is sufficient to press the first composite part toward the second composite part. Induction welding the second composite part to the first composite part is performed by applying induction heating while the flow of air is provided through the at least one opening.

Described herein are thermoplastic composites and methods of making thereof. The thermoplastic composites disclosed herein can include at least one randomly-oriented carbon fiber layer in the laminate to improve induction heating efficiency of the thermoplastic composite.

A composite structure and methods of forming composite structures are provided. A composite structure comprises a first composite part; a second composite part welded to the first composite part at a joint; and the joint between the first composite part and the second composite part comprising doped fibers.

A heat sink for use in electromagnetic welding of molded parts includes reinforcing fibers embedded in a matrix material, where substantially all of the reinforcing fibers are oriented unidirectionally in a fiber direction, where the reinforcing fibers have a thermal conductivity at room temperature from 100-1000 W/m. K and an electrical resistivity at room temperature from 0.5-10.m, and where the matrix material comprises a high temperature resistant material, optionally a thermosetting resin, having a glass transition temperature Tg above 350 C. The heat sink is used in a method of connecting surfaces of a first molded part and a second molded part by electromagnetic welding. Cooling of the outer surface of the first molded part is provided by the heat sink in direct contact with the outer surface.