ENHANCEMENT OF TRANSCRYSTALLINITY IN THERMOPLASTIC MATRIX COMPOSITES

THERMOPLASTICS, BEING SEMICRYSTALLINE MATERIALS ARE SENSITIVE TO PROCESS HISTORY. CRYSTALLINITY SIGNIFICANTLY AFFECTS MECHANICAL PROPERTIES. RELATIONSHIPS GOVERNING NUCLEATION AND CRYSTAL GROWTH IN FIBER-REINFORCED THERMOPLASTICS ARE POORLY UNDERSTOOD. CRYSTALS CAN BE PREFERENTIALLY NUCLEATED AT AND ORIENTED PERPENDICULAR TO FIBER SURFACES. THIS TRANSCRYSTALLINITY HAS BEEN SHOWN TO SIGNIFICANTLY INCREASE HEAT DEFLECTION TEMPERATURE. TRANSCRYSTALLINITY WOULD BE EXPECTED TO AFFECT OTHER MATRIX-DOMINATED PROPERTIES SUCH AS TRANSVERSE TENSILE STRENGTH, TRANSVERSE MODULUS, FATIGUE AND CREEP. SURFACE TREATMENTS, INVOLVING PLASMA CHEMISTRY PROCESSES, OF INTERMEDIATE MODULUS GRAPHITE FIBERS HAVE BEEN SHOWN TO INDUCE TRANSCRYSTALLINE GROWTH WHERE FIBER MANUFACTURERS' SURFACE TREATMENTS HAD NO EFFECT. THE EFFECT OF FIBER SURFACE CHEMISTRY ON TRANSCRYSTALLINITY, IF UNDERSTOOD, COULD BE USED TO DEVELOP THERMOPLASTIC COMPOSITES WITH IMPROVED MATRIX-DEPENDENT PROPERTIES. PROMOTION CONDITIONS FOR TRANSCRYSTALLINITY GROWTH WILL BE INVESTIGATED THROUGH ASTUDY INVOLVING FIBER PROCESSING, SURFACE CHEMISTRY CHARACTERIZATION, CRYSTALLINE MORPHOLOGY AND COMPOSITE MECHANICAL STUDIES. ANTICIPATED RESULTS SHOULD DEFINE OPTIMUM SURFACE CHEMISTRY CONDITIONS FOR TRANSCRYSTALLINE GROWTH. THE RESEARCH TEAM'S EXPERIENCE IN SURFACE TREATMENT OF FIBERS, SURFACE CHEMISTRY CHARACTERIZATION, THERMOPLASTIC PROCESSING AND COMPOSITE PROPERTIES COVERS ALL ELEMENTS OF THE PROGRAM.