No abstract

In this article, a new method to characterize the tear behavior of coated textiles using fracture mechanics is proposed. The energy dissipated in tearing (EDT) of as‐received and thermally aged samples of polyester fabric, polyvinyl acetate rubber coating, and textile‐coating composites was calculated and compared. The EDT of the coated fabric displayed a slightly smaller value than the fabric alone, whereas the EDT of the coating was found to be negligible when compared with the other two. The presence of the coating is believed to have a detrimental effect on the tearing behavior of the coated fabric as it hinders interfilament slippage. A master curve of EDT retention vs. aging time for noncoated and coated fabric samples was constructed using the time–temperature superposition principle and fitted using the Hill equation. Fourier transform infrared analyses carried out on aged fabric samples hinted at a possible chain scission process, whereas the crystallinity of fabric samples, calculated via differential scanning calorimetry, was found to decrease after thermal aging. Scanning electron microscopy images revealed an increase in surface roughness after aging that may reduce interfilament friction. These results, coupled to an increase in the adhesion strength between fabric and coating, are likely the cause of the reduction of EDT noticed in aged coated and noncoated fabrics compared with as‐received ones. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

The simultaneous puncture and cutting behavior of elastomers was investigated by pointed blades. Puncture/cutting tests by three-pointed blades were performed with different elastomer membranes, including butyl, neoprene, and nitrile rubbers. The fracture mechanisms associated to puncture/cutting were investigated. The quantitative material properties which control the puncture/ cutting resistance are obtained. The results have showed that the crack growth propagation is controlled by the material viscoelastic and the fracture behaviors of material, as well as the friction between the pointed blade and material. As evidenced from the fracture mechanism analysis, the friction contributes to the resistance of material against the simultaneous puncture and cutting by a factor of more than 60%. It has also been that the penetration force and the global fracture energy depend on the blade tip angle, the cutting edge angle, and the blade lubrication. Finally, an analysis of mixed-mode fracture based on puncture/cutting by pointed blades has been described. The crack propagation is a synergistic interaction between the fracture modes I and III.

Resistance to puncture or cutting by pointed blades is an important property of elastomer membranes and glove materials, making it necessary to define a fundamental criterion for measuring this resistance. However, the intrinsic properties controlling puncture/cutting crack propagation are still unidentified. This study has established a simple criterion describing the relationship between true fracture energy and the puncture/cutting process. Several samples of neoprene and nitrile rubber materials 1.6 mm and 3.2-mm thick were tested using three pointed blades having tip angles of 22.58, 358, and 568. It was found that both friction energy and true fracture energy contributed to global applied energy. True fracture energy, which is useful for in-depth study of the puncture/cutting process, was independent of material thickness, blade geometry, and blade lubrication. Furthermore, friction energy was approximately twice as great as true fracture energy.

Tearing resistance is an important parameter for evaluating the reliability of textile structures, especially in the case of protective materials. In order to better understand the individual contribution of the different mechanisms involved in the tearing process, a study of the relation between the fabric and yarn properties characterizing these mechanisms and the tearing energy has been carried out. For that purpose, polyester fabrics with two types of weave patterns and various values of filling yarn density and linear density were characterized in terms of tongue tear energy, yarn and fabric modulus, breaking force and elongation at break, yarn slippage, and yarn jamming. Data for all tested fabrics relied on a unique master curve when the tearing energy was expressed as a function of the transverse yarn slippage force. This demonstrates the strong contribution of transverse yarn slippage to the tearing process, a mechanism which has generally been overlooked in previous works on tearing. Relationships between the tearing energy and the other properties characteristics of the mechanisms involved in tearing of woven textiles were also observed. These results build the path toward the development of models for the tearing energy of textile structures. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers