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

The paper presents a macroscopic model of the non-linear stress/strain beha viour and the ultimate failure of a needled, woven carbon/carbon (C/C) comp osite, under tensile and shear loads parallel to the plies. The model is ba sed 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 develop ed by Ladeveze for composites. Modelling was guided by the experimental dat a on the matrix damage modes obtained from extensive microscopy examination of the test specimens under load. The model involves three scalar damage p arameters including two tensile parameters, and one shear parameter resulti ng from a combination of the tensile ones. Identification of the damage par ameters requires one off-axis (at 45 degrees in the plane of the plies), an d two on-axis (parallel to tow directions) uniaxial tensile tests. The mode l was validated with tensile stress/strain curves measured from various off -axis tests. The ultimate failure was predicted by the use of damage accumu lation criteria. (C) 1999 Elsevier Science Ltd. All rights reserved.