A unified fatigue failure criterion for unidirectional laminates

A unified fatigue failure criterion using micromechanics related to the fra cture plane has been developed to predict fatigue lives of unidirectional f ibre reinforced polymer composites subjected to cyclic off-axis tension-ten sion loading. Since the failure criterion incorporates both stresses and st rains it may be characterized as energy based. Accounting for the fibre loa d angle as well as the stress ratio is the novelty of this fatigue failure criterion. The criterion only requires the stress ratio to be known from th e experimental procedure. The relation between the applied load and the mic ro-stress and micro-strain field can be determined from a numerical method. The fatigue failure criterion has been verified by applying it to differen t sets of experimental data. Several fibre load angles, different fibre/mat rix combinations as well as stress ratios are covered. The predicted fatigu e lives are in good agreement with the experimental results for both differ ent fibre load angles and stress ratios. (C) 2000 Elsevier Science Ltd. All rights reserved.