Folding endurance and damage mechanisms of SiC fiber braided fabrics

Abstract

Aiming at the issues of poor toughness, low folding endurance, and susceptibility to damage of silicon carbide (SiC) fiber tows during repeated folding process, two-dimensional (2D) SiC fiber braided fabrics with varying braiding angles were prepared in this study. The folding endurance and damage mechanisms of SiC fiber fabrics under different folding conditions were investigated through repeated folding tests, tensile tests, and optical microscope measurements. The results revealed that when the folding angle was (+180°, −180°), the SiC fiber braided fabric with a lower braiding angle (α = 37.8°) exhibited a folding endurance number of 1984 times, while the medium angle fabric (α = 41.2°) had a value of 761 times, and the high angle fabric (α = 43.1°) achieved 1733 times. During the folding process, both interlaced abrasion between fiber tows and external folding loads affected the mechanical properties of SiC fiber tows and their fabrics leading to material damage. Initially, the folding load played a major role in determining fold endurance when there were fewer number of folds; however, as the number of folds increased, the influence of interlaced abrasion became increasingly significant. Ultimately, these combined factors led to progressive damage evolution until failure occurred in the fabrics. Among all tested samples, the SiC fiber braided fabric with a higher braiding angle (α = 43.1°) demonstrated optimal fold endurance performance, and it had superior characteristics such as higher fold endurance numbers along with lower force loss rates for fiber tows after multiple folds and fabric force loss rates following repeated folds.