Effect of woven structure on flexural and shear fracture behaviour of three-dimensional carbon-carbon composites

Abstract

The various structures and yarn-bundle spacing of 3D-5 (three directions, 5 mm), 5D-5 (five directions, 5 mm), and 3D-7.5 (three directions, 7.5 mm) preforms are fabricated into three-dimensional carbon-carbon (C/C) composites. The fracture behaviour is different due to the increased number of arrangement directions and fracture toughness. The flexural strength, short-beam shear strength, and microstructure of fractured specimens were investigated to study the mechanical behaviour of these composites. The results revealed that the strengths of the three-dimensional composites were larger than the five-dimensional ones in all reinforcement structures, but five dimensions were better than three dimensions in fracture toughness. The five-dimensional composites showed stepwise fracture, and the three-dimensional vertical fracture. In the aspect of yarn-bundle spacing, the flexural strength of the 7.5 mm type (spacing between twoZ axial yarn bundles is 7.5 mm) was higher than the 5 mm type, while the short-beam shear strength was contrary, Furthermore, according to SEM observations, the fractural surface was ruptured along theZ-axis, indicating that a stress concentration would exist in the fringe of theZ-axis, and that theZ-directional fibres arrested delamination propagation.