Abstract: The strain energy density ratio criterion for predicting cracking direction in composite materials is proposed. The Tsai-Hill criterion and Norris criterion of composite materials are extended to predict the cracking direction in composites. The three criteria are used to analyse the crack propagation problem of the unidirectional fibre composite sheet with various fibre directions. The predicted results are compared with those of the existing normal stress ratio criterion and strain energy density criterion.

Key words: composite maierials, cracking direction, unisotropy. lincur clustic fracture mechanics