Evolution of damage during the fatigue of 3D woven glass-fibre reinforced composites subjected to tension–tension loading observed by time-lapse X-ray tomography

B. Yu, R. Blanc, C. Soutis, P.J. Withers - Henry Moseley X-ray Imaging Facility, School of Materials, University of Manchester ; Aerospace Research Institute, University of Manchester, UK ; Thermo Fisher Scientific, Mérignac, FRANCE

Three dimensional (3D) composites were proposed over 40 years ago in an attempt to overcome the shortcomings of 2D laminates, by incorporating fibres into the through-thickness direction. 3D weaving offer significant manufacturing benefits as well as creating versatile textiles having a range of 3D architectures.

The development of fatigue damage in a glass fibre modified layer-to-layer three dimensional (3D) woven composite has been followed by time-lapse X-ray computed tomography (CT). The damage was found to be distributed regularly throughout the composite according to the repeating unit, even at large fractions of the total life. This suggests that the through-thickness constraint provides a high level of stress redistribution and damage tolerance. The different types of damage have been segmented, allowing a quantitative analysis of damage evolution as a function of the number of fatigue cycles. Transverse cracks were found to initiate within the weft after just 0.1% of life, followed soon after (by 1% of life) by longitudinal debonding cracks. The number and extent of these multiplied steadily over the fatigue life, whereas the spacing of transverse cracks along with weft/binder debonding saturated at 60% of life and damage in the resin pockets occurred only just before final failure.

How Amira-Avizo Software is used

The datasets obtained at different fatigue cycles were aligned using the registration module in Avizo. Subsequently a series of co-registered cross-sections parallel and perpendicular to the loading direction have been taken from each dataset to investigate the evolution of damage and the interaction between the different types of damage.