ANALYSIS OF CORD-RUBBER COMPOSITE RESPONSE BY USING THE NONLINEAR CONTINUUM DAMAGE MECHANICS APPROACH

The phenomenon of damage observed in cord-rubber composite laminates is the result of deformation, heat, chemical damage, and fracture. The micro cracks and the initial voids, present before any load is applied, grow through the mechanism of coalescence and generate permanent macroscopic cracks. A damage approach is proposed to describe the cumulative effects and damage evolution under cyclic loading and thermal and chemical impact. The approach parallels the continuum damage mechanics approach advocated by Kachanov and Rabotnov.(1,2) It is a phenomenological model that depends on laboratory testing to describe the evolution of damage and contains one scalar parameter to describe the collective effect of material damage. The following analysis is based on the premise that the cyclic interlaminar shear strain, coupled with the running temperature at the free edge, is the primary cause of damage. The model constants were derived from an alternating stress (S) against the number of cycles to failure (N) (i.e., S-N) curve at room temperature. The temperature effect on the material damage was accounted for by an Arrhenius shift function of the S-N curve. Numerical simulation of a composite laminate was conducted using the user subroutine UMAT in ABAQUS. The results presented reflect the accuracy of the proposed methodology to predict the location of the ensuing damage and the path of the damage propagation.