Shear deformation characteristics and defect evolution of the biaxial ±45° and 0/90° glass non-crimp fabrics

Currently, the shear pre-tension coupling behavior and evolution of various mesoscopic defects for the biaxial non-crimp fabric (NCF) are not revealed. Here, this work systematically conducted the picture frame shear with applied pre-tension and hemisphere forming for the +/- 45 degrees and 0/90 degrees glass NCF. In the picture frame shearing, it is identified that the effective shear response of the biaxial NCF in the positive shear mode should be characterized in the cycle 1 due to the irreversible destruction of the NCF architecture. Besides, the applying pre-tension is originally demonstrated to be capable of effectively suppressing the wrinkle defect and delaying the triggering shear angle of the wrinkle. Moreover, for the +/- 45 degrees NCF, the stitching thread suffers tension in positive shear mode, and the wrinkle is the main defect. In the negative shear mode, due to the non-pure shearing at high shear angle and compression of stitching thread, the mesoscopic defects, including bending and unit cell buckling of the stitching thread, are generated. In the hemisphere forming, it is revealed that the shear deformation is certainly arose in the tensile region of the +/- 45 degrees NCF due to the asymmetrical yarn shrink. The same fabric wrinkle and mesoscopic stitching thread defects are also originally identified, demonstrating the hemisphere forming is highly correlated to the large shear deformation. The results here provide a basic reference to suppress the defects in the performing process of the biaxial NCF.