Late-stage fatigue damage in a 3D orthogonal non-crimp woven composite: An experimental and numerical study

Uncovering the fatigue damage initiation and progression in uni-directional non-crimp fabric reinforced polyester composite

“…Previous studies [18,19] using X-ray CT highlighted the importance of taking the 3D aspect into account when considering the UD fibre fractures of quasi-UD NCF based composites. X-ray CT has been successfully used to monitor damage in fibre composites in several studies [18,19,[21][22][23][24][25][26][27][28][29][30][31][32][33][34], however it has the general disadvantage that cracks with an opening smaller than the resolution will not be visible (usually the voxel size is larger than 1µm). As a result, X-ray CT studies generally consider small specimens to obtain sufficient image resolution.…”

Fatigue damage assessment of uni-directional non-crimp fabric reinforced polyester composite using X-ray computed tomography

“…These systems make it easier to perform multiple longer timescale studies, albeit using much longer scan times compared to synchrotron CT. Since laboratory X-ray CT systems capable of micro resolution have only recently emerged, only a few studies to date [12,[22][23][24][25] have used laboratory systems to study material damage at the micro-structural level. The studies have tended not to consider individual fibre fractures because of insufficient resolution (e.g.…”

High temperature fatigue of carbon/polyimide 8-harness satin woven composites. Part II: Environmental effects

“…-the longitudinal elastic moduli, Ey ch , is defined from the data points of the first stages of traction using the method reported in [27]: a chord modulus is calculated as the slope of a straight line fitting the corrected machine data points over the strain range 0.03%-0.13%. The secant properties are generally strongly affected by creep effects, so corrected data on movable head displacement have been used for "elastic" properties calculation; -the longitudinal secant moduli, Ey ch Ey sec , has been calculated using the maximum longitudinal strain and the maximum longitudinal stress values for each load/unload cycle; -the hysteresis area, A, is used to characterize the load/unload cycles in full, while the previous two properties characterize only the load stage.…”

“…This last value is kept until the end of the test for the air and 2 bar N2 specimen, while a slightly rise is seen for the 2 bar O2 specimen just before the failure. This final rise for the 2 bar O2 specimen, could be due to the stick-slip frictional sliding ( [27], [28]).…”