STP1224

    Tear Resistance of Roofing Membranes

    Published: Jan 1994


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    Abstract

    Roofing membranes are subjected to a tear stress when stretched near a notch, cut, or nail hole. The force required to initiate or propagate tears in roofing membranes was studied using various standard test methods. The materials used in the study included reinforced EPDM (ethylene propylene diene monomer), PVC (polyvinyl chloride), and MBM (modified bitumen). The results were obtained from the load-displacement diagrams using the mean of three or five peaks on the test charts, as required. The tests showed significant differences in the values obtained by various methods. Five methods were used to investigate the tearing mechanism: four were existing standard methods and a fifth method involved grips designed at the National Research Council of Canada (NRCC). In this new method, the specimen is held in a top and bottom pair of grips that swivel as the tearing progresses. The gripping configuration in the tensile tester produces stress concentration in a very small area around the root of a tear and minimizes the tearing effort. Each membrane sample was tested with all five methods. Comparison of the results suggests that the swivel grips provide a more realistic simulation of tearing phenomena because tearing occurs at the lowest applied force.

    Keywords:

    roofing membrane, swivel grips, tear resistance, tear strength, tensile tear, tongue tear, trapezoid tear


    Author Information:

    Dutt, O
    Research Officer, Institute of Research in Construction, Materials Lab., National Research Council of Canada, Ottawa,

    Paroli, RM
    Research Officer, Institute of Research in Construction, Materials Lab., National Research Council of Canada, Ottawa,

    Lei, W
    Technical Officer, Institute of Research in Construction, Materials Lab., National Research Council of Canada, Ottawa,

    Mebrahtu, H
    Technical Officer, Institute of Research in Construction, Materials Lab., National Research Council of Canada, Ottawa,


    Paper ID: STP12898S

    Committee/Subcommittee: D08.20

    DOI: 10.1520/STP12898S


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