RANDOM GLASS MAT REINFORCED THERMOPLASTIC COMPOSITES .3. CHARACTERIZATION OF THE TENSILE MODULUS

Random glass mat thermoplastic composites, which can be thermostamped to form complex deep-drawn parts with ribs and bosses, are excellent materials for making low-cost stiff parts with relatively high impact strength. An earlier effort, aimed at understanding the scatter in the mechanical properties of these materials showed that the tensile modulus in these materials can vary by a factor of two over a 12.7-mm distance. To better characterize the local tensile modulus for such materials, measurements of the local tensile moduli of long, thin, 12.7-mm wide strips along both thin edges (left and right) of the specimen and across the face are used to show that the tensile modulus is well approximated by the arithmetic mean of the local left- and right-edge tensile moduli. This arithmetic mean modulus, which is shown to correlate with the local density, is a better practical measure of the response to tensile loads.