Experimental and numerical investigation of the effect of gaps on fatigue behavior of unidirectional carbon/epoxy automated fiber placement laminates

Abstract

Automated fiber placement (AFP) process provides high potential to repeatability and flexibility required for manufacturing of complex parts in many industries. Performance of such parts can be influenced by AFP manufacturing induced defects such as gaps and overlaps. In this work, the effect of gaps on fatigue behavior of unidirectional carbon/epoxy laminates was investigated. Tension–tension fatigue tests were conducted on defected samples and compared to reference samples free from defects. Infrared thermography technique was used for monitoring of damage propagation during fatigue loading. Moreover, a fatigue progressive damage model (FPDM) was developed and applied to laminates containing gaps to predict fatigue damage progression and failure. The experimental results revealed that the effect of gaps depends on the maximum applied stress during fatigue. The higher is the applied stress, the higher is the reduction in fatigue life. Good agreement was found between the results of fatigue life prediction from the FPDM and the experimental results for defected specimens.