COMPOSITES CONTAINING GLASS SPHERES AND FIBERS .2. TENSILE, FLEXURAL, AND SHEAR STRENGTHS

Tensile, flexural, and shear tests on glass fiber-polyester pultrusions containing glass spheres show that the spheres reduce the tensile strengths when both rigid and flexible polyesters are used, but some increase in flexural strength is obtained with the flexible resins. Small additions of spheres increased the shear strengths, but for sphere volume fractions greater than about 0. 2, the shear strength declined. A silane coupling agent on the spheres increased the strength of the rigid resin composites, but had little effect with the flexible resin. Some of the results could be due to the lack of straightness of the fibers caused by the presence of spheres having diameters greater than the fiber diameter. However, when the fibers were not present, the sphere filled matrices showed very diverse behavior. The results presented here indicate that even in the absence of fibers, simple models are unlikely to be successful in explaining the properties.