Synergistic optimization of Z-pin architecture and curing process for composite laminates: Thermal self-regulation and interfacial bonding recovery

Z-pinning enhances through-thickness reinforcement of carbon fiber-reinforced polymer laminates, yet the insertion process induces mesoscale resin-rich zones whose thermo-chemo-mechanical (TCM) mismatch with the constraining pins can trigger interfacial debonding during autoclave curing. This study develops an integrated TCM finite element and statistical optimization framework to elucidate and mitigate such process-induced defects. Analytical scaling analysis reveals a Biot-number-governed thermal self-regulation mechanism: the high through-thickness conductivity of translaminar Z-pins maintains a near-isothermal internal field, rendering the thermal gradient insensitive to both process and geometric variables. Response surface analysis further identifies decoupled driving mechanisms—the global degree of cure is predominantly governed by the macroscopic thermal trajectory, whereas peak interfacial residual stress is controlled by the nonlinear coupling between heating rate and dwell temperature, modulated by Z-pin diameter and density. NSGA-II multi-objective optimization is subsequently employed to construct the Pareto-optimal frontier, yielding an optimized cure cycle that simultaneously enhances the degree of cure and substantially reduces the peak interfacial residual stress relative to the conventional manufacturer-recommended baseline. Microstructural examination confirms the complete recovery of interfacial bonding integrity, transitioning from visible debonding under the standard cycle to intact Z-pin/resin-rich interfaces under the optimized protocol.