CHARACTERIZATION OF FINITE-LENGTH COMPOSITES .3. STUDIES ON THIN-SECTIONS EXTRACTED FROM MOLDINGS (WAFERS)

Through-thickness aspects of composites are studied by means of struct ural investigations and mechanical testing of thin 'wafers' machined f rom molded specimens. Two injection molding regimes, namely the Dynami c and Static mode, have been used to induce different fibre orientatio ns in polypropylene (PP) reinforced with glass (g) and polyamide (PA) reinforced with carbon (c). Novel experimental techniques such as the 'rebound technique', uniaxial compressive yield and flexural testing o f circular discs have been used for evaluation of longitudinal and tra nsverse properties. A strong anisotropy of properties in composite mol dings is governed by the spatial fibre orientation. This depends on bo th the matrix and the processing conditions used with the system PP/g being more regularly structured (skin/core morphology) than PA/c. A sa tisfactory agreement in the area a) structure/performance and b) exper iment/theory has been achieved.