High-fidelity analytical modeling of asymmetric CFRP composites using Reissner–Mindlin theory and hygroscopic degradation

Abstract

Multi-stable carbon fiber-reinforced composites with asymmetric ply layouts have shown promising potential for creating multi-functional structural systems. To design and analyze these complex composites, high-fidelity and computationally efficient analytical models are crucial. To this end, Hyer and Dano formulated the first model four decades ago based on classical lamination theory (CLT). Surprisingly, despite many follow-up studies to refine this analytical approach, current models still follow the same fundamental ingredients used in Hyer and Dano’s original work. As a result, they all inherited the same limitations. For example, they ignore the interlaminar stresses and lack a rigorously calibrated hygroscopic term. To overcome these limitations, we propose a new analytical modeling approach by adopting the Reissner–Mindlin theory and hygroscopic degradation. This new model introduces in-plane rotations as two additional degrees of freedom and a combined expansion coefficient for the epoxy matrix materials. Compared to finite element simulations and experiment data, the new model can estimate the interlaminar stress reasonably well (especially regarding its concentration near the edges) and predict the laminates’ external shape more accurately than an equivalent Hyer’s model. The new model can also accurately predict the reduction in the laminate’s curvature and snap-through force in different design configurations, as well as their linear correlation to the moisture content levels. Overall, the results of this study present a fundamental advancement in the analytical modeling of asymmetric multi-stable composite laminates, offering a broad and versatile foundation for designing and analyzing the next generation of multi-functional composite structures.