Mechanical properties of knitted fabric reinforced polypropylene composites

Abstract

A study is conducted on the effects of cooling conditions on flexural properties of aramid fiber knitted fabric (AFKF) and glass fiber knitted fabric (GFKF) reinforced thermoplastic polypropylene composites. To study these effects, composite laminates are fabricated under a molding pressure of 3 MPa for 20 min, then consolidated from the melt at different cooling conditions: rapid cooling, i.e. quasi-quenching, and gradual cooling. Flexural tests are carried out on specimens in two directions: wale and course. Evaluation on thermal properties and morphology is studied using a differential scanning calorimetry (DSC). Flexural properties are little sensitive to the cooling rates; however, gradually cooled specimens show higher level of crystallinity than rapidly cooled specimens. Furthermore, flexural strengths display higher in the wale than in the course directions. SEM micrographs of fracture surfaces reveal poor adhesion between the fiber and polypropylene matrix.