A combined experimental and numerical approach for characterizing ply-level damage in tape-laminate composites subjected to biaxial loading

A new test method is developed for progressive characterization of ply-level damage in composites subjected to biaxial loading. A novel biaxial cruciform specimen is designed to promote damage formation in the gage region and enable ex-situ imaging of damage using X-ray computed tomography. Tests are performed using carbon/epoxy laminate subjected to 1:2 tension-tension loading at room temperature, which are compared to simulations from a progressive-damage analysis (PDA) software, BSAM™. The experimental results show that, for the stacking sequence tested, biaxial loading leads to complex intralaminar fracture dominated by short and closely spaced stitch cracks. The PDA simulations show qualitatively similar results; however, the load at fracture initiation is over-predicted and the stitch crack growth is not as extensive. Critical evaluation of the experimental and numerical results is used to suggest further development of the proposed methodology with the ultimate aim of studying damage evolution in laminates subjected to cryobiaxial loading.