The effect of the weaving architecture and the z-binding yarns, for 2D and 3D woven composites on the low-velocity impact resistance of carbon fibre reinforced composites, is investigated and benchmarked against noncrimp fabric (NCF). Four architectures, namely: NCF, 2D plain weave (2D-PW), 3D orthogonal: plain (ORT-PW) and twill (ORT-TW), were subjected to 15 J impact using a 16 mm-diameter, 6.7 kg hemispherical impactor. Nondestructive techniques, including ultrasonic C-scanning, Digital Image Correlation (DIC) and X-ray computed tomography (CT) were used to map and quantify the size of the induced barely visible impact damage (BVID). The energy absorption of each architecture was correlated to the damage size: both in-plane and in-depth directions. The 3D architectures, regardless of their unit-cell size, demonstrated the highest impact resistance as opposed to 2D-PW and the NCF. X-ray CT segmentation showed the effect of the higher frequency of the z-binding yarns, in the ORT-PW case, in delamination and crack arresting even when compared to the other 3D architecture (ORT-TW). Among all the architectures, ORT-PW exhibited the highest damage resistance with the least damage size. This suggests that accurate design of the z-binding yarns’ path and more importantly its frequency in 3D woven architectures is essential for impact-resistant composite structures. ... Read more

This study is devoted to the damage characterization of Non-Crimp Fabric (NCF), 2D plain-woven (2D-PW) and 3D orthogonal plain-woven (ORT-PW) carbon/epoxy laminates, subjected to compression after multiple-impact loading, using Acoustic Emission (AE). The ultrasonic C-scan images showed that the interlaminar damage area induced by the single and 3-impact in ORT-PW architecture is 3 and 2 times smaller than NCF and 2D-PW architectures respectively. The impacted specimens were then subjected to the in-plane compression load. Two indices, one based on the mechanical response and another one based on the AE behavior of the laminates, were proposed to compare the performance of different architectures. These indices showed that the ORT-PW had the best performance among all the architectures. Finally, AE was used to distinguish the different damage mechanisms including: matrix cracking, intra and inter-yarn debonding, defected-fiber breakage, intact-fiber breakage and z-binder fiber breakage in the CAI tests of the architectures. ... Read more

This paper investigates the effect of the fabric architecture and the z-binding yarns on the compression after multiple impacts behavior of composites. Four fiber architectures are investigated: non-crimp fabric (NCF), 2D plain weave (2D-PW), 3D orthogonal plain (ORT-PW) and twill (ORT-TW) weave. The specimens were subjected to single and multiple low-velocity impacts at different locations with the same energy level (15 J). Non-destructive techniques including ultrasonic C-scanning, X-ray CT and Digital Image Correlation (DIC) are employed to quantitatively analyze and capture the Barely Visible Impact Damage (BVID) induced in the specimens. Although the absorbed energy was approximately the same, damage was the least in 3D woven architectures. In the case of compression after impact, 3D woven composites demonstrated a progressive damage behavior with the highest residual strength (∼92%) while 2D plain weave and NCF specimens showed suddenly catastrophic damage and the residual strength of ∼65% and ∼55% respectively. ... Read more