SURFACE, INTERPHASE AND COMPOSITE PROPERTY RELATIONS IN FIBER-REINFORCED POLYMERS

The aim of this study is to demonstrate the relations between surface, interphase and different composite properties in composites of carbon and glass fibres and thermosets (epoxy resin) or thermoplastics (poly amide, polypropylene). The surface characteristics of variously treate d carbon and glass fibres have been determined by contact angle measur ements, using a capillary penetration technique, and zeta potential me asurements. Micromechanical tests (single-fibre pull-out) have been ap plied to model composites to establish the interphase properties. Bulk composites have been manufactured by impregnation with resins and cur ing by hot pressing or pressing of commingled yarn samples (continuous reinforcing fibres) or twin-screw extrusion and injection moulding (s hort reinforcing fibres). The composite properties have been tested by tensile and shear tests. Contact angle and electrokinetic measurement s permit detection of differences in the surface treatment of glass an d carbon fibres. Measurements of shear strength by pull-out, fibre fra gmentation and yarn tensile shear tests show comparable results and co rrelate to the macromechanical properties.