Thermoanalytical investigation of composite lamination

Abstract Glass cloth reinforced epoxy resins are commonly used to make composites. The performance of these laminates depends strongly on optimizing cure kinetics and rheology for a given chemical composition and temperature/pressure profile. Aborted flow tests (weight percent resin squeezed out during a given temperature/pressure cycle) is frequently used to emulate lamination processes and/or to evaluate new formulations. The cure reaction was monitored using differential scanning calorimetry, rheology, and dielectrometry. These techniques show that the cure kinetics are controlled by the temperature profile. The viscosity and the macroscopic flow, however, are affected by the temperature profile, i.e. decrease in viscosity with rising temperature, as well as the cross‐linking kinetics which lead to an increase in viscosity. Gravimetric and thickness measurement indicated a non‐uniform resin distribution across the laminate, with a lower resin content found at the edges. Macroscopic flow is controlled by three dimensional heat transfer, which leads to a dynamic temperature distribution and, concomitantly, to a cure/rheology profile. This was demonstrated graphically by marking layers of reinforced resin and monitoring the movement of the markers.