Resistance welding has been demonstrated as a viable technique for joining thermoplastic composites. Extensive research has been conducted in previous studies on the processing and postprocessing evaluation of coupon‐sized resistance welded specimens using this thermoplastic fusion bonding technique. This work focuses on the manufacturing and evaluation of large‐scale resistance welds used to join carbon fiber (CF)/polyetheretherketone (PEEK) thermoplastic composite parts. Applications using the present resistance welding technology are assessed, and potential applications of resistance welding are discussed. The sequential resistance welding process is introduced as an approach to large‐scale welding that increases joint quality and performance while maintaining modest pressure and weld power requirements. The single‐step and alternate multiple‐step (sequential) techniques are implemented for large‐scale resistance welds of CF/PEEK adherends comolded with polyetherimide (PEI) (i.e., the Thermabond® process). Nondestructive ultrasonic evaluation, mechanical testing, fractography, and microscopy show that: (1) a higher weld uniformity was obtained with the multiple‐step weld than the single‐step weld; and (2) uneven heating and overheating were minimized by reducing the heating element length within the bond region through the use of the sequential resistance welding process. The different welding techniques produce a large variation in lap shear strength; direct comparison of the weld quality and lap shear strength shows that the sequential resistance welding process yields a superior bond. With the principles developed in this investigation, resistance welding can be used to join large‐scale thermoplastic composite parts with consistent, high levels of performance and quality. © 1997 John Wiley & Sons, Inc. Adv in Polym Techn 16: 279–295, 1997

The need for effective and reliable joining methods continues to grow as the use of thermoplastic composites becomes widespread. It is now possible to join largescale components with the development of an automated sequential resistance welding process. The thermal history generated by the heating element placed at the interface between adherends determines the quality and performance of the welded joint. This article presents a thermal analysis for the resistance welding of large-scale components that overcomes the limitations of previous models. To simulate welding of the interface, a heat generation term was incorporated that accounts for the Joule heating of graphite fibers in the heating element. A parametric study was conducted to investigate the influence of welding parameters and assess the uniformity of interface temperatures. Components were joined by the resistance welding process to obtain experimental verification. Regions of localized overheating where potential current leakage may occur were identified as a function of process parameters. Insights on promoting more uniform heating for the resistance welding process are discussed.

The Manufacture of Advanced Composite Submarine Structures (MACSS) program is part of the Advanced Research Projects Agency (ARPA) Maritime Systems Technology Office, Advanced Submarine Technology (AST) program. The program is developing the material product forms, processes, and equipment for automated fabrication of lowcost composite submarine structures. These developments will be demonstrated through fabrication and delivery of subscale and fullscale components of the Composite Dry Deck Shelter (CDDS). This paper will discuss the McDonnell Douglas Aerospace (MDA) thermoplastic fiber placement process, material selection, and machine that make fabrication of largescale submarine structures possible.

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