ON MATRIX CRACK-GROWTH IN QUASI-ISOTROPIC LAMINATES - I - EXPERIMENTAL INVESTIGATION

Matrix crack growth behaviour under quasi-static and mechanical fatigu e loadings has been studied in quasi-isotropic (0/90/ - 45/ + 45)(s) G RP laminates. Derailed experimental observations were made on the init iation and growth of individual cracks in +/- 45 degrees and 90 degree s plies. Degradation of elastic properties of the laminates due to mat rix cracking was observed and recorded. The quasistatic results were c ompared with baseline data from a crossply (0/90)(s) laminate. Distinc tly different crack growth behaviour was observed in quasi-isotropic l aminates under quasi-static and fatigue loadings, suggesting a strong influence of load history. A higher density of +/-45 degrees cracks an d hence greater stiffness reduction appear to be the characteristics o f fatigue damage in quasi-isotropic laminates. (C) 1997 Elsevier Scien ce Limited.