Fracture failure analysis and bias tearing strength criterion for a laminated fabric

摘要

This paper deals with the fracture failure analysis on plain woven laminated fabrics used in stratospheric airship structures. A series of uniaxial tensile and central slit tearing tests were carefully conducted on bias specimens, and the corresponding tensile and tearing properties, including failure mechanisms and material strengths, of a laminated fabric were discussed. Results show that laminated fabrics are typical direction-depended materials, and their failure characteristics vary greatly with the bias angles. Typical tearing stress-displacement curves of the laminated fabric could be defined as four characteristic regions: a co-deformation region, a yarn extension region (or shear deformation region), a plateau region, and a post peak region. Among bias specimens, there are many obvious differences in tearing behaviors in terms of maximum displacement, damage mode, curve slope, and number of stress peaks, which could be attributed to the material orthotropy and different failure mechanism of constituent materials. Unlike results of tensile strength, there is a W-shaped relationship between tearing strength and off-axis angle, with a local strength peak at 45 degrees angle. Based on the Tsai-hill criterion, a new tearing strength criterion consisting of two parts, including a U-shaped and an inverted V-shaped part, is proposed for this laminated fabric. Comparisons between the experimental and calculated results for the laminated fabric are performed, and the strong agreements demonstrate that the proposed criterion is feasible and accurate.