Buckling Performance of Patch-Based Composite Panels: Numerical Optimization and Experimental Evaluation

Abstract

Material offcuts generated during composite manufacturing retain much of the structural ca-pability of the original material but are too small to be of use in conventional manufacturing. Thus they are commonly recycled in processes that reduce their structural utility. Patched composites offer an alternative approach in which discrete patches are cut from these offcuts, then arranged and consolidated into structural laminates. This study investigates the structural efficiency of patched laminates for a stiffness-driven application: panel buckling under uniaxial compression. A symmetric tiled-patch laminate with staggered adjacent layers was modeled using finite el- ement analysis. While maintaining fixed patch geometry and grid alignment, individual patch fiber orientations were varied to maximize the critical buckling load. A gradient-based opti- mization method using eigenvalue buckling analysis, central-difference sensitivities, and line search was utilized. Geometrically nonlinear finite element analysis was then used to evaluate the converged designs, followed by experimental compression testing of manufactured panels. The results showed that patch-wise orientation tailoring can substantially alter the buckling re- sponse, while manufacturing-induced thickness variation and geometric imperfections strongly influence the experimentally realized behavior. Overall, this work characterizes the tradeoff between structural efficiency and material reuse associated with patched composites and provides an optimization framework for designing buckling-resistant patched laminates. The findings provide structural design insight relevant to the continued development of Fiber Patch Placement and related approaches for higher-value reuse of composite manufacturing waste.