Thermo-mechanical coupled dynamic monitoring model for interlaminar strain in unidirectional laminated composites

Accurate characterization of curing-process-induced eigenstrain distributions is critical for predicting residual stresses in laminated composites. This work integrates theoretical analysis, numerical computation, and in-situ experimental testing to comprehensively investigate the transmission and evolution of interlaminar strain within composite laminates over a full curing cycle. Theoretically, a novel calculation approach for interlaminar strain in laminated composites is developed based on a multi-scale framework. A representative volume element (RVE) with dual interface layers is constructed for stress analysis. In-situ measurements using polyimide-coated optical fibers (PIOF) are performed to capture interlaminar strains within Ω-shaped laminates across the complete curing cycle; the evolution characteristics of interlaminar strain are analyzed alongside numerical simulation results. Furthermore, quantitative analysis is carried out to characterize the through-thickness interlaminar strain distribution in composite laminates with various ply orientations. The results demonstrate that interlaminar strain exhibits nonlinear decay under coupled thermo-mechanical loading. The proposed theoretical model effectively captures interlaminar strain propagation in layered laminates during the full curing cycle. This study enhances the predictive capability of existing models for interlaminar strain distributions in autoclave-cured unidirectional T700/epoxy laminates.