Mechanical properties of bi-axial warp-knitted fabric T700/BMI6421 composites

Comparing with the unidirectional(UD) cloth T700/bismaleimide(BMI)6421 composite, mechanical properties of warp-knitted fabric T700/BMI6421 composite were studied. Bending properties and interlaminar shear properties of warp-knitted fabric T700/BMI6421 composite were tested. The variety in fabric structure caused by warp-knitted thread were demonstrated with metallographic microscope and SEM images. It is shown fiber distortions caused by warp-knitted thread decrease the bending performance. The bending modulus is 26% lower than the unidirectional cloth reinforced composite in the 45° direction. The interlaminar shear performance is improved by stitching structure which make the fiber layer tighter. The interlaminar shear strength(ILSS) is about 13% higher than the unidirectional cloth reinforced composite in the 0° direction. It is confirmed that traditional unidirectional cloth could be replaced by warp-knitted fabric in liquid composite molding process.