Manufacturing of ultra-thin thermoplastic TRAC longerons

Deployable composite structures such as TRAC (Triangular Rollable and Collapsible) longerons are highly attractive for large-scale space applications due to their compact stowage and passive deployment capabilities. Conventional TRAC longeron manufacturing relies on autoclave-cured thermoset composites, which limits scalability. This study presents an out-of-autoclave manufacturing approach for ultra-thin thermoplastic longerons using thin-ply PEEK-based prepreg systems. A modular 3-step process (comprising laminate consolidation, web welding, and flange shaping) is applied to evaluate the effects of processing parameters and prepreg quality. Laminates are assessed via mechanical testing, computed tomography (CT), differential scanning calorimetry, and thermogravimetric analysis, revealing that fiber distribution homogeneity and thickness control are critical for void suppression, forming behavior, and overall laminate quality. Complete longerons are manufactured and analyzed using high-resolution laser scanning and CT analysis. Shape accuracy is found to strongly correlate with laminate uniformity, with flange radius deviations of up to 48% being observed in materials with poor fiber architecture. The most uniform prepregs yield nearly cylindrical flanges and geometric distortion of less than 10%. These results demonstrate that, with careful process control and prepreg selection, out-of-autoclave manufacturing can achieve structural and geometric quality comparable to autoclave-based production, enabling scalable fabrication of deployable composite structures.