Fracture toughness characterization of polyethylene and polyester nonwoven composite films

Fracture toughness is a material property that quantifies the ability of a material to resist the propagation of a flaw. As a material property, fracture toughness should be independent of geometric parameters such as initial tear length, gage length and film thickness. The J-integral fracture toughness of thin homogeneous polyolefin blown films has been studied in the past. Our earlier research has shown the fracture toughness of both the homogeneous and nonwoven polyethylene composite films to be independent of such parameters. The homogeneous films are currently in use for high altitude scientific balloons. The nonwoven composite films are being evaluated as potential candidates for long duration ballooning applications. This paper focuses on the J-integral fracture toughness characterization and tearing strength measurement procedure of nonwoven composite films. Room temperature fracture toughness and tearing strength data obtained for four films are presented in this paper. The testing procedure and analysis for both the strip biaxial J-integral technique and ASTM trapezoidal tear test method employed in this study are outlined.