Numerical Modeling of Friction Behavior of CF / PEEK With Consideration of Machining‐Induced Surface Roughness and Subsurface Damage

ABSTRACT Machining‐induced surface defects and subsurface damage significantly modify the local mechanical properties of carbon‐fiber‐reinforced thermoplastic composites (CFRTPs), thereby affecting the frictional performance of the machined surfaces. Accurate prediction of friction behavior as influenced by surface quality is critical. However, existing finite element friction models rely on ideal smooth‐contact assumptions and discrete‐damage descriptions, limiting their ability to capture actual contact behavior and accurately predict frictional response. In this study, a cross‐scale finite‐element friction modeling framework is proposed to simultaneously account for machined surface roughness and subsurface damage distribution. Surface roughness effects are characterized by equivalent representations of the real contact area and contact stiffness, while subsurface damage is described using a depth‐wise gradient approach. The effects of surface roughness and subsurface damage distribution on the frictional response are analyzed, and the predictive capability of the proposed model is quantitatively evaluated through comparison with a previous model. The results demonstrate that the proposed approach more accurately captures the contact behavior of machined CF/PEEK surfaces and significantly improves frictional response prediction, providing a reliable basis for the development of high‐accuracy cross‐scale friction prediction models.