LAUSR

Abstract Due to the jamming action in the manufacturing process, local curvature and fiber reorientation are inherent in nature to the yarn in 3D four-directional braided composites, which results in different failure modes comparing with the constant yarn cross-section. Therefore, a novel unit cell model with jamming-action-induced yarn deformation was developed in this study. Then using the developed unit cell model, the progressive damage process of 3D four-directional braided composites under unidirectional tension was examined on the basis of Murakami-Ohno damage theory. Numerical results reveal stress concentration and higher stress level induced by the jamming action. As a consequence, predicted stress-strain curve by employing the developed unit cell model agrees well with the experimental data. In addition, earlier damage initiation and lower predicted strength are observed, compared with the original unit cell model without considering the inherent yarn deformation. Furthermore, owing to the jamming-action-induced yarn deformation, the yarn longitudinal damage firstly fails at the regions where the yarn is curved, and subsequently damage fails near the damaged elements in the first stage.