Study of post-impact behaviour of thin carbon/epoxy laminates subject to fatigue tensile loading

This article concerns the experimental and numerical study of post-impact damage propagation in thin carbon/ epoxy woven composite laminates loaded in fatigue tension. Low velocity normal drop weight impact tests are first performed. Post-impact fatigue tensile tests are then carried out. They are controlled in displacement. The monitoring is based on Digital Image Correlation and RX tomography. The influence of the impact energy and the tensile fatigue loading on the post-impact damage propagation is studied. The damage propagation is governed by matrix damage, with the emergence of tows/resin splittings and intra-tows crackings as well as delamination when the plies have different orientations. When the impact energy or the displacement level increases, the postimpact damage initiates sooner and propagate faster. In some cases, that can lead to a quasi-instantaneous failure identical to that observed for quasi-static tensile loading. The FEM based semi-continuous approach, initialy developped for the modelling of impact damage, is extended to fatigue loading for carbon/epoxy woven laminates. Fatigue damage laws, based on experimental observations are implemented. The modelling well correlates the experimental results in terms of damage propagation scenario and speed depending on the number of cycles for laminates made up of plies with the same orientation.

Automated summary

This article discusses the experimental and numerical study of post-impact damage propagation in thin carbon/epoxy woven composite laminates subjected to fatigue tension. The study shows that the damage propagation is governed by matrix damage, and increases in impact energy or displacement level lead to faster initiation and propagation of post-impact damage. The FEM based semi-continuous approach effectively models the damage propagation scenario and speed depending on the number of cycles for laminates with plies of the same orientation.