QUASI-IMPACT DAMAGE INITIATION AND GROWTH OF THICK-SECTION AND TOUGHENED COMPOSITE-MATERIALS

Results are presented for a study of damage initiation and growth in thick-section and toughened continuous fiber-reinforced composites resulting from a spherical indenter/impactor. The proposed analytical/computational model consists of several sub-models. A three-dimensional mesh generator is used for generating initial meshes for laminated composites containing various matrix cracks and delaminations. A stress analysis is developed in the framework of finite deformation for calculating stresses and strains of the composites with and without internal damage. A robust contact analysis proposed for handling the contact condition of cracked interfaces for matrix cracks/delaminations induced during indentation loading. A failure analysis is developed for predicting the damage initiation and propagation. A fracture mechanics based, simplified criterion is proposed for predicting the critical load for delamination growth. The proposed model predicts that the damage of thick-section composites may be initiated from the layer right below the indenter due to the compressive load, or the interior shear matrix cracks due to transverse shear. This contradicts the conclusions for thin, brittle laminated composites, in which surface cracking is in general the initial damage mode. It is shown that the delamination induced by the shear cracks is dominated by fracture modes II and III for growth of thick-section composites due to indentation loading. It is also interesting to observe that complicated contact zone exists for different delaminations.