Effect of cure schedule on physical/mechanical properties of graphite/epoxy composites

The physical and mechanical properties of 8-ply graphite/epoxy laminates subjected to three cure cycles with varying heat-up rates are studied. Reverse-phase liquid and IR chromatography, differential scanning calorimetry, and rheological measurements are utilized to examine changes in reaction enthalpy, viscosity, and chemical structure. Glass transition temperature, tensile strength, and fracture toughness are measured; fiber volume, resin, and void content and decomposition profiles are evaluated with texture and thermogravimetric analyses. The data reveal that slower heat-up rates produce larger reaction enthalpies and composites with higher resin content; however, faster heat-up rates yield composites with lower resin content and higher glass transition temperatures. It is observed that the mechanical properties are unaffected by postcuring. 32 references.