Coupling mechanism and process optimization of pore-mechanical properties in hot-press forming of CCF/PEKK laminates

Abstract

In view of the high strength and high reliability requirements of composite pallet covers for load-bearing drones, this study focuses on the quantitative coupling relationship between process parameters–porosity–mechanical properties in CCF/PEKK hot-pressing forming. The Box–Behnken response surface method was used to establish the regression model of forming temperature, pressure and holding time on flexural strength, interlaminar shear strength (ILSS), and porosity (R ² > 0.98). Results show that: for every 1% increase in porosity, the flexural strength decreases by about 83 MPa, and the ILSS decreases by about 3.4 MPa; the flexural strength and ILSS have a strong positive correlation (r = 0.967), indicating that both are strongly correlated with porosity; the flexural strength exhibits a stronger correlation with porosity compared with ILSS, as bending stress tends to concentrate around pores while shear stress can be redistributed. The temperature × pressure interaction shows significant synergy on pore control (p = 0.0008). SEM confirmed that low-porosity samples showed matrix ductile fracture characteristics, while high-porosity samples showed interface debonding. Optimal process via multi-objective optimization: 370.14°C, 8.12 MPa, 21.97 min, with verification error < 5%. This suggests a quantitative “process–pore–performance” relationship, providing a useful reference and preliminary process window.