The invention relates to the use of a low Tg compatible resin as an adhesive layer for the welding of a thermoplastic composite structure to a thermoplastic or thermoset structure. The invention is especially good for the welding of large parts, such as wind turbine halves and spar caps. A useful thermoplastic composite is one formed by the infusion and curing of long fibers by a reactive acrylic liquid resin system, such as ELIUM® resin systems from Arkema.