Numerical simulations of the splitting tensile behaviour of needle-punched carbon/carbon composites

Carbon/carbon (C/C) composites are materials developed for applications requiring excellent mechanical and thermal properties at elevated temperatures. Needle-punching has been used to improve the delamination resistance of C/C composites; however, its effect on tensile behaviour has yet to be fully understood. This work studies the splitting tensile behaviour of needle-punched C/C composites numerically using experimentally validated finite element (FE) simulations with a damage initiation criterion. The splitting tensile test, comprising the diametral loading of flattened Brazilian discs (FBDs), was employed for the simulations and validation. A mesoscale model of the composite FBD specimen was built, in which each composite layer was explicitly modelled, including cohesive interfacial behaviour. The composite needle fibre bundles were modelled using truss elements. The FE simulations showed the crucial role that needled fibre bundles play in the C/C composite tensile performance by carrying tensile stresses perpendicular to the loading direction and reducing the levels of localised deformation in the central region of the specimen at the early stages of loading. Furthermore, the damage initiation criterion showed that when the needle fibre bundles are included in the FE simulation, the extension of damaged areas is less than in the simulations without needled fibre bundles. In addition, the numerical results showed that increasing the number of needled fibre bundles reduced the extension of the damage in the matrix.