Micro-mechanics analysis of damage for unidirectional composite laminates under tri-axial compression

A new micro failure criteria based on the physical failure mechanism was proposed from the standpoint of micro-mechanics. The criteria follows Mohr-Coulomb criteria, in which damage type and failure mechanism under compressive load was emphasized. This study argued that shear damage will be prevented by compressive stress on the fracture surface. Fiber compressive failure mode was also researched in depth. A concept of shear strength on fiber kinking surface was introduced in fiber kinking failure criteria. Failure prediction and quantitative evaluation for lamina in the Second World Wide Failure Exercise were carried out. The prediction results were compared with Puck, Pinho, Cuntze, Carrere, Tsai-Ha, Hansen and Huang criteria. Assessment results show that the criteria proposed in this study ranks first under tri-axial load. The effect on the strength of matrix by hydrostatic pressure was researched. The results show that influence factor is only relevant with fracture angle of matrix under single compressive load. The important divergence that whether the failure envelope is "open" or "closed" among each strength criteria in WWFEII was analyzed and discussed. This study suggests that there is no universally accurate answer, because it is connected with fiber volume fraction, mechanical properties, hydrostatic pressure and fracture angle of matrix under single compressive load.