Description: The Thermoplastics Development for Exploration Applications (TDEA) project focused on thermoplastic composite (TPC) joints for space structures by developing and maturing TPC materials, design capabilities, analysis tools and techniques, and manufacturing processes. The TDEA team evaluated TPC material systems and performed an assessment of the current capabilities for the design, analysis, and manufacture of commercially available TPC material systems for large-scale space structures and on-orbit applications. The TDEA project has improved NASA's TPC processing and manufacturing capabilities, developed an understanding of advanced TPC joining technique(s) relevant to space environments and applicable to unitized and/or reconfigurable composite structures and advanced structural analysis capabilities for the design and analysis including failure prediction of TPCs including joints. Composite materials enable NASA's science and exploration missions where lightweight, high-performance structural solutions are required. Currently composites are commonly manufactured with thermoset composite (TSC) materials that undergo a chemical reaction when heated and fully cured. Conventional thermosets cannot be remolded or remelted after the first cure. Interfaces must often contain mechanical fasteners which can adversely affect mass and alter structural performance. The performance of bonded TSC joints is also highly sensitive to surface preparation techniques and bonding processes. Programs are often not able to take advantage of the structural efficiencies offered by composite structures due to characterization and certification challenges, particularly with respect to joints. Alternatively, thermoplastics are fully chemically reacted and can be reprocessed with heat and pressure alone. They can be remelted, remolded, and consolidated as necessary without causing any chemical changes, which makes their joining processes more straightforward. Unitizing structures with thermoplastic composite materials show promise to increase structural efficiency and reduce mass. TPC material properties are sensitive to joining processes, so care must be taken to produce strong and reliable TPC joints. TDEA focused on TPC joints to create large monolithic structures that save on manufacturing time, part count, and weight. Ultimately this could enable in-space assembly and manufacturing of large monolithic space structures.

Benefits: Thermoplastic composites have many benefits over traditional thermoset composites that can lead to simplified designs for lower cost and higher performance. Thermoplastics are fully chemically reacted and processable with heat and pressure alone enabling shorter cycle time. Thermoplastics can be reheated, remolded, and cooled as necessary without causing any chemical changes enabling reprocessing, and repurposing through disassembly and reassembly of bonded areas not possible with currently available thermoset materials. This is feasible but will require additional development to be at the point where it is practical and ready for infusion. Thermoplastic joining processes are more straightforward than chemical bonding with reduced process steps than thermoset composites. The process steps reduced are those most often associated with poor bond reliability (i.e., surface preparation), thus thermoplastic composites processes may turn out to be more reliable. Using thermoplastic material enables the ability to create large monolithic or unitized structures that are structurally efficient saving manufacturing time, part count, and weight. Unitized thermoplastic structures with their fused parts can reduce certification requirements and conservatism. The development and maturation of joining technologies for thermoplastic composites will benefit NASA's science and exploration missions where mass and performance optimized structures are critical.