Mechanical properties of knitted fabric reinforced polypropylene composites

A study is conducted on the effects of cooling conditions on flexural prope rties of aramid fiber knitted fabric (AFKF) and glass fiber knitted fabric (GFKF) reinforced thermoplastic polypropylene composites. To study these ef fects, composite laminates are fabricated under a molding pressure of 3 MPa for 20 min, then consolidated from the melt at different cooling condition s: rapid cooling, i.e. quasi-quenching, and gradual cooling. Flexural tests are carried out on specimens in two directions: wale and course. Evaluatio n on thermal properties and morphology is studied using a differential scan ning calorimetry (DSC). Flexural properties are little sensitive to the coo ling rates; however, gradually cooled specimens show higher level of crysta llinity than rapidly cooled specimens. Furthermore, flexural strengths disp lay higher in the wale than in the course directions. SEM micrographs of fr acture surfaces reveal poor adhesion between the fiber and polypropylene ma trix.