Modelling of the stress/strain behaviour of a carbon/carbon composite with a 2.5 dimensional fibre architecture under tensile and shear loads at room temperature

The paper presents a macroscopic model of the non-linear stress/strain behaviour and the ultimate failure of a needled, woven carbon/carbon (C/C) composite, under tensile and shear loads parallel to the plies. The model is based upon continuum damage mechanics concepts for the description of damage evolution, and the approach to plasticity for the description of inelastic strains induced by matrix damage, according to the general approach developed by Ladevèze for composites. Modelling was guided by the experimental data on the matrix damage modes obtained from extensive microscopy examination of the test specimens under load. The model involves three scalar damage parameters including two tensile parameters, and one shear parameter resulting from a combination of the tensile ones. Identification of the damage parameters requires one off-axis (at 45° in the plane of the plies), and two on-axis (parallel to tow directions) uniaxial tensile tests. The model was validated with tensile stress/strain curves measured from various off-axis tests. The ultimate failure was predicted by the use of damage accumulation criteria.