Damage characteristics of open-hole laminated composites subjected to longitudinal loads

The damage mechanism of open-hole composite laminates subjected to longitudinal loads was studied by a three-dimensional (3D) progressive damage analysis (PDA) model, which took two essential issues, fiber kinking and shear non-linearity, into consideration. Furthermore, a parameter, damage width, was introduced to indicate the damage extent of the specimen. A good agreement between the simulation and the experiment results demonstrates the effectiveness of the proposed model. Specifically, some interesting characteristics during the damage process were revealed by the finite element analysis. It was found that in open-hole tension (OHT) test, the damage appearing first was matrix tension damage, while fiber micro-buckling emerged first in open-hole compression (OHC) test. From the load- damage width curves of open-hole laminates, it was observed that as long as any fiber damage in 0 degrees ply spreads to the outer edges, the specimen loses its loading capacity. However, this phenomenon, interestingly, cannot be found in 90 degrees or +/- 45 degrees plies. This characteristic pointed out that the damage of 0 degrees plies in laminated composites can be used as an indicator to reflect the damage extent of composite structures.