Functionally Sorted Laminated Material for Damage Resistance and Damage Tolerance

Shi Hua - Department of Mechanical Engineering, University of Bath

In this thesis, the damage mechanisms and failure behaviours of hybrid laminates panels due to out-of-plane impact and near-edge and on-edge impact were investigated. The impact tests include low-velocity dynamic impact test and quadra-static indentation. Compression after impact was conducted to discover the residual stiffness in the post-test samples and the improvement of damage resistance and damage tolerance are analysed. A novel testing and inspection method had been developed by combining X-ray CT-scan and quadra-static indentation to observe formation of damage gradually and clearly. Finite element models for beams and plates were created to study the interaction between layers and a correlation had been established by an analytical model using through-thickness-shear stress. By adding glass layers into carbon laminates, the hybrid laminates display increases in structural efficiency of up to 32% in comparison to full carbon laminates with identical impact energies. In the on-edge and near-edge impact tests, for blocked stacking sequence, the delaminations and cracks are contained in the middle region of sample, which increases residual stiffness and increase structure damage tolerance.