Method for alleviating residual tensile strain in thermoplastic welds

A welded thermoplastic composite comprising at least two fiber-reinforced resin composites joined by a fiber-reinforced, thermoplastic resin weld region, the weld region including:

• (a) a metal susceptor having a width defining a welded bondline between the composites, the susceptor for producing heat at the bondline to weld the composites along the bondline with a thermoplastic resin weld;
• (b) a resin layer defining a weld on each side of the susceptor along the bondline for forming the weld upon heating of the susceptor to a temperature sufficient to soften the resin, the weld being formed by mixing the softened resin layer with softened resin from the composites, the resin being substantially the same material as the resin in the composite;
• (c) at least one layer of fiber reinforcement in the resin defining the weld on each side of the susceptor, wherein the fiber reinforcement is woven fiberglass substantially the width of the susceptor and is in sufficient amount to alleviate residual tensile strain in the resin of the weld.

A composite assembly formed by thermoplastic welding to join at least two fiber-reinforced resin composites with a fiber-reinforced thermoplastic weld around a susceptor along a bondline, comprising:

• (a) a first and second carbon fiber-reinforced resin composite arranged to define interfacing faying surfaces along a bondline;
• (b) a metal susceptor between the faying surfaces, the susceptor being adapted for heating inductively when exposed to an oscillating magnetic field;
• (c) a thermoplastic weld surrounding the susceptor and having fiber-reinforced resin joining the composites along the faying surfaces, the weld including at least two plies of fiberglass fiber reinforcement extending along the bondline in the resin substantially the width of the susceptor independent from fiber in the composites to relieve residual tensile strain in the resin, at least one ply of the fiber reinforcement being in the resin of the weld on each side of the susceptor, the fiber reinforcement being in the resin between the susceptor and one, respective faying surface of one of the composites, the resin in the weld being substantially the same resin as the resin in the composites.