Time-dependent interfacial friction model and rib deformation simulation for flexible-tool forming of CFRP grids in process-sensitive regimes

Controlling rib deformation is a key challenge in flexible-tool forming of carbon fiber reinforced polymer (CFRP) grid structures. In this study, fiber Bragg grating (FBG) sensors embedded in the flexible tool were used to monitor in situ strain evolution during curing, and the corresponding interfacial shear stress was inversely determined based on local stress equilibrium. Guided by lubrication theory, a cure-dependent anisotropic interfacial friction model was established from the monitored data and implemented as a tangential boundary condition in a coupled curing-deformation simulation. The simulation incorporated resin flow-compaction, thermo-chemical evolution, and viscoelastic constitutive behavior to predict the width deformation of helical and hoop ribs. The predicted rib widths agreed well with experimental measurements, with an average prediction accuracy of 93.4%. The results further revealed a critical rib deformation transition temperature, providing guidance for autoclave pressurization timing. This work provides an experimental–numerical framework for predicting and controlling rib deformation in CFRP grid structures.