Thermal analysis and degradation of properties in carbon fiber/epoxy laminate riveting at high temperatures

A riveting process was developed to fasten carbon fiber/epoxy composite laminates. This process heats a thermoplastic composite rivet blank placed into the joint hole, above melt temperature, to form a rivet fastening the joined components. This process poses a threat to the integrity of the structure's epoxy matrix. To verify the state of matrix degradation, a pin-loaded mechanical test was applied on composite test pieces heat treated at various temperatures. The heat treatment was specifically designed to recreate the riveting process thermal cycle. A finite element model of the heat treatment was produced to obtain the time and temperature exposure of the test piece during the heat treatment. For use in the finite element model, emissivity was characterized through infrared image analysis, and thermal conductivity was characterized with an inverse method. The results show that a riveting process at nominal temperature of 350 degrees C will not affect the bearing properties of the composite laminates. However, the process at 450 degrees C does affect the bearing properties.