Effect of Yarn Reduction Types on the Mechanical Response and Damage Mechanism of 3D Woven Composites Subjected to Low-velocity Impact

Yarn reduction is the core technology of near-net forming conical rotating components. This paper presents the influence of yarn reduction defects on the low-velocity impact (LVI) and compression after impact (CAI) damage mechanism of 3D woven composites. Three kinds of specimens with different yarn reduction defects, no yarn reduction (NO-YR), half row-yarn reduction (HIN-YR), and all row-yarn reduction (AIN-YR), were tested using drop weight LVI and CAI equipment. X-ray micro-computed tomography (Micro-CT) and Digital Image Correlation (DIC) technique were used to identify the damage distribution and damage development of the impact of 3D woven composites. Results indicated that the yarn reduction defects can reduce the LVI and CAI mechanical characteristic values of 3D woven composites. The maximum deflection, permanent deformation, and energy absorption rate of HIN-YR and AIN-YR are about 3% and 6% lower than NO-YR, respectively. At the same impact energy, NO-YR damage was the least and AIN-YR damage was the most severe. Furthermore, compared with AIN-YR, HIN has higher CAI strength. More importantly, yarn reduction changed the damage mechanism of the specimens. The final failure of NO-YR is decided by debonded, whereas that of HIN-YR and AIN-YR are mainly influenced by yarn breakage and delamination.