Volume 5, Issue 5 (September 1977)
A Comparison of Methods for Determining the Shear Properties of Glass/Resin Unidirectional Composites
This paper describes and compares three methods of test for determining the interfacial adhesive strength of the glass/resin bond in reinforced plastic (RP) unidirectional composites. Measurement of the shear properties of these materials is of fundamental importance to the fiberglass manufacturer developing optimum sizing systems for the surface treatment of glass fibers used as plastics reinforcements. A new test, developed explicitly for the shear strength determination of pultruded cylindrical composites, is described and data obtained thereby are compared with similar results obtained by torsional and short-beam methods. Unlike this new notched-rod test, both the latter tests may occasionally give tensile rather than shear failures, thus rendering their usefulness questionable, since the shear strength of the composite has not been measured under such circumstances.
Contrary to earlier work of other researchers, the current experiments suggest that the shear strength of the RP composite may exceed that of the resin matrix when the bond at the glass/resin interface has been optimized.