Influence of meso-scale parameters on the large-deformation behaviour of ultra-thin woven fibre composites

Abstract

Ultra-thin woven composite laminates are widely used in deployable space structures, in which they experience large curvatures during both folding and deployment. Under such conditions, these laminates exhibit pronounced non-linear bending behaviour characterised by a progressive reduction in stiffness. Accurate prediction of this response is essential for reliable structural design. This study presents a comprehensive numerical framework to investigate the non-linear bending behaviour of ultra-thin two-ply plain-weave composite laminates using a representative unit cell based homogenisation approach. A multi-scale finite element model was developed that integrates an explicit geometric representation of the woven architecture, geometric non-linearity associated with large deformations, strain-dependent material non-linearity of tows and cohesive traction–separation behaviour at tow–tow and inter-ply interfaces. The proposed framework enables direct evaluation of the laminate moment–curvature response and extraction of homogenised stiffness parameters. The numerical predictions show strong agreement with experimental results over the full range of curvatures investigated. The model accurately captures the progressive reduction in bending stiffness with increasing curvature and reveals that this degradation arises from the combined influence of geometric effects, inter-tow interactions and material non-linearity of carbon fibres. At moderate curvatures, stiffness reduction is dominated by geometric mechanisms, including tow flattening, cross-sectional deformation and neutral-axis shift. At higher curvatures, cohesive damage and micro-slipping between adjacent tows become the primary contributors. Inclusion of resin layers between plies was shown to be critical for accurate stiffness prediction, as the resin constrains inter-ply motion and increases the number of effective contact interfaces, enabling close replication of experimentally measured initial bending stiffness. A comparative investigation of fibre in-phase and out-of-phase stacking arrangements demonstrated that ply alignment has a significant influence on bending stiffness. Overall, the proposed homogenisation framework provides a robust and physically grounded tool for predicting the complex bending behaviour of ultra-thin woven composites. In addition to reproducing experimental responses with high accuracy, the approach enables extraction of homogenised ABD stiffness matrices suitable for macro-scale modelling and design of deployable composite space structures.