Methods for Evaluating Shear Strength of Plastic Laminates Reinforced with Unwoven Glass Fibers

摘要

Several methods were employed to evaluate the shear strength of plastic laminate panels 1/8 inch in thickness and reinforced with unwoven glass fibers. Shear values at 0 degrees to the fibers obtained by the Johnson shear and blockshear methods showed relatively good agreement. Shear strength values at 0 degrees to the fibers obtained from axial tests on notched specimens were found to depend upon the shear length between notches and the type of lateral restraint. Values obtained from short-span beam tests were affected by combined failures, depending on the shear span-depth ratio and the method of loading. Shear strength values at 90 degrees to the fibers by the block-shear method were about two-thirds of values obtained by the Johnson shear method and by compression tests of double-notched specimens with 1/8 inch between notches. Because of the stress concentrations that develop in each of these test methods, it is felt that none of the methods discussed here give shear strength value as high as would occur in pure shear. (Author)