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Investigation of Methods for Evaluating Unwoven Glass-fiber-reinforced Plastic Laminates in Flexure

Author : Karl Romstad

Publisher :

Page : 41 pages

File Size : 37,23 MB

Release : 1964

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Book Description

Three plastic laminates reinforced with unwoven, unidirectional glass fibers were evaluated over varying spans under both midpoint and two-point loading improve accepted flexure test procedures for these materials. Also investigated were the effects of radius of loading nose, length of overhang, and different two-point loading systems on properties of 1/8-inch laminates. Results of these evaluations indicated that present test methods often result in failures that do not accurately evaluate the outer fiber strength of the material. Horizontal shear failures could be eliminated by using a specimen with a span-depth ratio greater than 16. For a long specimen, a correction factor must be applied to the conventional moment expression to include the effect of horizontal components of force at the reaction supports. Compression failures beneath the load points were eliminated either by using a 0.01-inch-thick metal plate beneath a loading nose of 1/8-inch radius, increasing the loading nose radius, or increasing the specimen spandepth ration. (Author).







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

Author : Karl Romstad

Publisher :

Page : 36 pages

File Size : 43,87 MB

Release : 1964

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Book Description

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).





Methods for Evaluating Tensile and Compressive Properties of Plastic Laminates Reinforced with Unwoven Glass Fibers

Author : Karl Romstad

Publisher :

Page : 28 pages

File Size : 45,56 MB

Release : 1964

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ISBN :

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Book Description

Methods of obtaining strength and elastic properties of plastic laminates reinforced with unwoven glass fibers were evaluated using the criteria of the strength values obtained and the failure characteristics observed. Variables investigated were specimen configuration and the manner of supporting and loading the specimens. Results of this investigation indicate that satisfactory tensile failures can be obtained by reinforcing the shank portion of the tension specimen with 1/32-inch sheet aluminum. Variation of tensile specimen geometry was inconclusive, with at least partial failures always occurring in the shank portion. Difficulty was encountered in trying to obtain accurate compressive strength data on the composite material comprising these laminates. Some acceptable compression failures were obtained using a 5-1/8-inch-long specimen clamped at the ends and supported laterally by the standard FTM-406 jig. Failures varied for different laminates, indicating that resin properties may control failure when the material acts as a composite. (Author).