Failure assessment of 3D woven composites under compression after low-velocity impact

The failure mechanism of 3D woven composites subjected to compression loading along principal/off-axis direction after low-velocity impact (LVI) was assessed by experimental and numerical methods. The low-velocity impacts under 26.8 J and 80 J energies were applied to the specimens with off-axis angles of 0 degrees and 45 degrees. It can be observed that the impact damages are direction-dependent, which is determined by the weft and warp orientations. By performing the compression-after-impact (CAI) tests, it is found that the CAI strength along principal direction is more sensitive to the low-velocity impact than that along off-axis direction. A finite element dynamic analytical method was established, considering four off-axis angles (0 degrees, 30 degrees, 45 degrees and 60 degrees). The results show that the extension direction of the impact damage changes regularly with the off-axis angle. During the compression, the small off-axis angle can make the specimen prone to produce a sudden crushing failure determined by the fiber failure due to the high axial stress. As the off-axis angle increases, the matrix damage gradually holds the dominant position due to the growing shear effect, which makes the specimen produce a ductile failure governed by the accumulated matrix failure.

Automated summary

The failure mechanism of 3D woven composites under compression loading after low-velocity impact was studied using experimental and numerical methods. The study found that the impact damages are direction-dependent, determined by the weft and warp orientations. The compression-after-impact tests showed that the strength along the principal direction is more sensitive to the low-velocity impact. A finite element dynamic analysis method was established, and the results revealed that the extension direction of impact damage changes with the off-axis angle, with smaller angles leading to sudden crushing failure determined by fiber failure, and larger angles leading to ductile failure governed by accumulated matrix failure.