A general numerical model for anisotropic mechanical response of arthropod cuticle

Abstract Arthropod cuticle is a widespread biological composite with a broad range of mechanical anisotropy, which arises from a fiber-layered architecture. While the cuticle commonly exhibits helicoidal chitin-protein fiber architecture, specific structural parameters, such as rotation angle, lamella thickness, and sublayer number, differ across taxa and anatomical regions. These variations are thought to reflect adaptations to specialized mechanical functions. However, linking these structural features to mechanical behavior remains experimentally challenging. Therefore, we present here a general numerical model that studies the anisotropic mechanical behavior of layered fibrous materials typical of arthropod cuticle. The model reproduces the three-dimensional helicoidal arrangement of chitin fibers and their interactions using a simplified phenomenological approach based on movable cellular automata. Without tuning to specific experimental parameters, the model captures key features, such as anisotropic deformation under directional indentation and energy dissipation patterns. The simulated anisotropy index falls within the experimentally observed range for natural cuticles, supporting the idea that architecture alone can strongly influence mechanical response. Our literature-based analysis highlights a consistent trend observed in the numerical model: increased matrix stiffness/sclerotization is often associated with reduced anisotropy, likely due to more isotropic mechanical reinforcement. This study provides a general modeling framework for understanding structure-property relationships in fibrous biological composites.