RANDOM GLASS MAT REINFORCED THERMOPLASTIC COMPOSITES .2. ANALYSIS OF MODEL MATERIALS

The mechanical properties of random continuous glass mat reinforced composites, as determined by standard tensile tests, are known to have a very large scatter. New test procedures have shown that the tensile modulus in these materials can vary by a factor of two over a 12.7‐mm (½‐in) distance. The elastic modulus in a 150 × 305‐mm (6 × 12‐in) plaque can vary by a factor of three. In order to understand the effects of the gauge length on the properties of such materials measured in tensile and flexural tests, a simple model, in which the tensile elastic modulus is modulated by a spacewise sinusoidal variation, has been analyzed. The effect of the functional form of the modulus variation has been assessed by analyzing a square‐wave variation. Copyright © 1990 Society of Plastics Engineers