Co-authors​ :

 Sutharsanan NAVARATNARAJAH (UNITED KINGDOM), James KRATZ (UNITED KINGDOM), Mark SCHENK (UNITED KINGDOM) 

The growing interest in dry fibre manufacturing processes is driven by their potential to achieve increased production rates at reduced cost. Non-crimp fabrics (NCFs) are a preferred choice for dry fibre processing because of their higher deposition rate and superior mechanical performance compared to woven materials. However, the formability of NCFs is limited over complex geometries due to the absence of 'cross-over points' between tows, preventing rotation and thus shear deformations. The dominant deformation mechanism during the forming is in-plane shear, which enables the fabric to be formed over 3D geometries. Exceeding the allowable limit for shearing in NCFs during forming can lead to undesired out-of-plane wrinkling, resulting in a reduction in the mechanical performance of the final part. This study adopts a novel approach to manufacturing composite structures based on NCFs by employing origami techniques.

Engineering origami is a rapidly maturing field that seeks inspiration from the art of origami to solve challenging engineering problems. Applications range from deployable space structures to miniaturised medical devices and mechanical metamaterials. Origami can create complex 3D geometries from a flat sheet by undergoing isometric deformations such as crease folding and sheet bending, i.e. no material stretching and shearing. Our aim is to create composite structures by folding flat sheet materials using curved-crease origami. This approach would minimize stretching and shearing deformation in the forming process, thereby minimizing the occurrence of wrinkling defects, albeit with a trade-off in achievable geometries. However, sharp edges, as employed in traditional paper folding, are not feasible for continuous fibre composites due to the risk of fibre distortion, misalignment, or potential damage. Therefore, a corner radius is introduced at the folds; this leads to localized non-developability along the creases, resulting in fibre stretching or shearing. A feasibility study is conducted to assess the forming capability of NCFs over geometries inspired by curved crease origami. Using two curved creases, a simple 3D geometry is generated with the middle surface defined as a cylinder of varying curvature, producing a cylindrical surface on one side and a conical surface on the other, as depicted in the attached Figure. This study aims to assess the forming capability of NCFs over curved-crease origami-inspired geometries with the goal of minimizing defects.