Strain based service time estimation for angle-ply laminates

The long term behaviour of ±45°-angle-ply laminates of carbon/epoxy was studied. Due to the absence of 0°-layers angle-ply laminates are subject to cyclic creep. To investigate the time dependent behaviour, creep tests and constant amplitude fatigue tests at different stress ratios were performed. The assumption that the extent of creep depends on the fatigue mean stress was verified and the interaction between creep and fatigue was determined. Based on creep strain data a general fatigue damage metric was defined and conservative service times were estimated.