Three-dimensional (3D) reinforcement by stitching is effective in improving the impact resistance of composites. Stitching, however, adversely affects the composite's in-plane mechanical responses, and alters its damage mechanisms due to stitch-induced irregularities. We experimentally investigate the effect of two important stitch parameters, stitch density and thread diameter, on the damage characteristics of 3D stitched multidirectional composites under in-plane tension using X-ray radiography, X-ray micro-computed tomography and digital image correlation (DIC). Our study shows that composites stitched with thicker thread exhibit improved tensile strength due to effective hindrance of edge-delamination. We also found that stitch thread affects damage behaviors. A higher number of transverse cracks develops in the middle portion of thin 90° fiber tows; the inter-crack distance is reduced by dense stitching. DIC is able to identify the cracks that appear in resin-rich channels and distinguish strain fields due to different stitch densities.
|Number of pages
|Composites Part A: Applied Science and Manufacturing
|Published - Apr 2015
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors would like to thank the Tokyo Metropolitan Government for the research funding provided under Asian Network of Major Cities 21 (ANMC-21) project. Part of this research was supported by MUST baseline research funds. We acknowledge the advise from Mr. Ali Moussawi on the DIC technique. We also thank Dr. Karl Leo of the Solar and Photovoltaic Engineering Research Center (SPERC) of MUST for the use of the micro-CF facility.
ASJC Scopus subject areas
- Mechanics of Materials
- Ceramics and Composites