The impulse resistance welding (IRW) process is modelled using a three-dimensional transient finite element model (FEM) featuring heat transfer and consolidation. The welding of single lap joints is simulated for APC-2 laminates, with additional PEEK film inserted at the welding interface. The effects of the power signal on (a) temperature uniformity in the welding interface and (b) processing times are investigated. Two welding configurations are evaluated; in the first one, the heating element outside the welding stack is left in-air, while in the second case, it is embedded in a conductive medium in order to improve temperature homogeneity within the welding interface. Based on criteria of consolidation and thermal degradation, optimum processing windows were simulated.