Investigating the Potential of Using Off-Axis 3D Woven Composites in Composite Joints’ Applications

Abstract

The effect of circular notch has been evaluated for three different architectures of three-dimensional (3D) carbon fibre woven composites (orthogonal, ORT; layer-to-layer, LTL; angle interlock, AI) through open-hole quasi-static tension and double-lap bearing strength tests in the off-axis (45°) direction. Damage characterisation is monitored using Digital Image correlation (DIC) for open-hole testing and X-ray Computed Tomography (CT) for double-lap bearing strength test. The off-axis notched 3D woven composites exhibits minor reduction (less than 10 %) of the notched strength compared to the un-notched strength. DIC strain contour clearly show stress/strain localisation regions around the hole periphery and stress/ strain redistribution away from the whole due to the z-binder existence, especially for ORT architecture. Up to 50 % bearing strain, no significant difference in the bearing stress/bearing strain response is observed. However when ORT architecture was loaded up to failure, it demonstrates higher strain to failure (~140 %) followed by AI (~105 %) and lastly LTL (~85 %). X-ray CT scans reveal the effect of the z-binder architecture on damage evolution and delamination resistance. The study suggests that off-axis loaded 3D woven composites, especially ORT architecture, has a great potential of overcoming the current challenges facing composite laminates when used in composite joints' applications.

Recent advancements in mechanical characterisation of 3D woven composites

“…This was attributed to the fact that in the half-hole test the load carrying yarns were cut along the cross section for testing. In the case of the double-lap test, the warp-loaded specimens demonstrated the highest stiffness but the off-axis loaded specimens had the highest bearing strength, which supports the argument proposed earlier by (Saleh et al 2016a) that although off-axis 3D woven composites demonstrate less stiffness, they possess significantly better damage resistance/tolerance capabilities up to failure.…”

“…Only one recent study by Saleh et al (Saleh et al 2016a) reported the notched response of 3D woven composites, in off-axis orientation, by an open hole tension test. The study considered three different architectures namely ORT, AI and LTL and focused only on the off-axis direction.…”

“…9b) has been conducted for ORT, AI and LTL architectures in the off-axis direction by Saleh et al (Saleh et al 2016a). X-ray CT was used to visualise the internal damage of the failed specimens.…”

“…This is considered the only study that focuses on thick 3D woven composites as opposed to relatively thinner ones reported by (Warren et al 2015b;Saleh et al 2016a). Two tests were conducted namely as the pin-bearing test on half-hole and the double-lap pin-bearing test.…”

Joining of Cf/SiC Ceramic Matrix Composites: A Review

“…For aerospace applications, as reported by NASA, the X-37B and X-38 aircrafts employed a large number of C f /SiC composites in their nose cone [25], leading edge wing and engine components [11,26,27,29]. For nuclear applications, C f /SiC composites are used as the cladding materials in pressurized water reactors and flow channel insert materials in thermonuclear fusion reactors [29,30,32]. In most cases, typically, C f /SiC composite components are usually geometrically complex in shape and always need to join with other materials to form a certain engineering part.…”