Study on tear propagation of a fabric laminate in biaxial stress

Tear propagation is the typical fracture mode of fabric laminates, which is affected by stress and damage size. With the use of high strength fabrics, high performance laminates emerge continually. In this paper, tear propagation of a high strength fabric laminate coating polyurethane used in high altitude lighter-than-air vehicle (LTA) is studied. Cross-shaped specimens, central size 5cm×5cm, are scissored out to test tear propagation strength in biaxial stress by a tailor-made testing machine. The damnification is a cut slit in weft direction, warp fibers cut off. The cut slit is in the middle of specimens, including 0cm (scatheless specimens), 1cm, 2cm and 3cm in length. Tear propagation is observed and the strength is noted simultaneously to gain the mechanical properties of the fabric laminate. The tensile strength of the laminate is 424N/cm, and it descends to 263N/cm in cut slit length of 1cm. Subsequently, two methods based on stress field and linear elasticity fracture mechanics are introduced to analyze the tear strength, which is validated well by test results, and the coefficients of empirical formulae are obtained. It is useful to analyze the limit length and the limit stress for the fabric laminate with initial damage.