Study on tearing tests and the determination of fracture toughness of PVC-coated fabric

Abstract

In this study, detailed uniaxial in-plane tearing tests including uniaxial central, single-edge notched, and trapezoidal tearing tests of a type of polyvinylchloride (PVC)-coated polyester fiber fabric were conducted. Two types of tearing failure modes, brutal and progressive, were examined. In addition to differences in the descending sections of the stress–displacement curves and the membrane surface morphology near the crack, it was found that the uniaxial central tearing test could be replaced by the corresponding single-edge notched tearing test to minimize the usage of test materials. The configuration of the single-edge notched specimen, including the gauge length and width, was investigated to determine the conditions under which the tearing resistance of the practically nearly infinite membrane surface can be studied with finite-size specimens. To obtain the fracture toughness GIC, which characterizes the ability of materials to prevent crack growth, a theoretical method and two test methods were introduced. After comparing the methods, the test method based on the area of the parallelogram obtained from the zigzag wave in the descending section of the load–displacement curves was proved to be superior. The value of GIC obtained with this simple test method was relatively stable, and it could be used to evaluate the tearing resistance and calculate the tearing strength of the coated fabrics.

Tearing behaviors of polytetrafluoroethylene coated fabric under uniaxial in-plane tearing tests

“…For larger gauge lengths, brittle failure occurs with more possibilities. 31 In this work, the extension of tearing is an important research focus; in order to observe and investigate the extension process, a smaller gauge length of 200 mm 26 is accepted. The sample sizes are presented in Figure 2(a).…”

“…Furthermore, the strain distribution at the crack section, which is the most representative, has been studied extensively. 31 , 32 In the case of the acquisition of the strain distribution at the crack section when tearing initiates, by marking the central position of all the yarns on the surface before testing, according to the marking position, the strain of each yarn at the slit section can be obtained based on the photos captured using the DIC equipment during the testing. In this treatment, the strain at the center of a yarn is used as the average strain in the yarn to approximate the uneven strain in this yarn.…”

“…Current researches also commonly focus on the onset of tearing and critical tearing strength. [23][24][25][30][31][32][33][34] Therefore, although it is quite difficult to simulate the process after tearing initiates when adopting a macroscopic continuum model, attention is paid to the tearing initiation and the preceding stage, which are crucial and meaningful to real-life projects. For the onset of tearing, the stress criterion is adopted, and an assessment is introduced as the average stress inside different multiples of the yarn spacing from the crack tip reaches the uniaxial tensile strength.…”

“…By assuming the stress distribution of the yarns, they proposed a tearing strength prediction model. Bao et al 31 conducted uniaxial tearing tests, single-edge notch tearing tests, and trapezoidal tearing tests of a PVC coated fabric, while considering various influencing factors. Based on the results, the fracture toughness G IC obtained using the theoretical and test methods is introduced and compared.…”

“…Most of the above researches primarily focus on one or two tearing methods, and the study subject mainly comprises the tearing strength and its influencing factors, fracture parameters, or numerical simulations. As indicated by recent researches, the fracture toughness is receiving significant attention 24,26,27,31 and is currently a hot research subject. Researches focusing on the correlation between different methods are limited.…”