Fatigue and Damage Assessment of CFRP Material Using Digital Image Correlation

Fatigue testing of a Carbon Fiber Reinforced Polymer (CFRP) in tension-tension loading has been conducted. In-situ surface strain measurements were performed to examine the gradual elongation of the specimen as this relates to stiffness loss and fatigue damage. A methodology capturing the specimen at peak load has been developed, including an automated trigger mechanism that activates the camera at the desired cycle count. The material tested was a Unidirectional (UD) Non-Crimp Fabric (NCF) with carbon fibers and an epoxy matrix. The fatigue test results revealed a wide scatter in the mid-range of the high cycle fatigue region. By studying the strain in the early fatigue loading cycles and the stiffness loss over time, benchmark of the fatigue performance between different material samples could be carried out, explaining the scatter in the fatigue testing. It could be observed that the fatigue limit of the UD CFRP material in the fiber direction is in the magnitude of 80 % of the material's Ultimate Tensile Strength (UTS). (C) 2021 The Authors. Published by Elsevier B.V.