Non-isothermal in situ dielectric cure monitoring for thermosetting matrix composites

Cure monitoring is important for the quality and productivity of composite structures during the manufacturing process of thermosetting resin matrix composites. Since isothermal cure cycle was used in the previous researches for the dielectric cure monitoring, temperature effect could not be included effectively. In this study, dynamic cure cycle was adopted for the investigation of the composite cure process under non-isothermal conditions. Experimental results obtained from both differential scanning calorimetry (DSC) and dielectrometry under the same cure curing conditions were compared to predict the degree of cure of thermosetting resin matrix composites during the curing process. The sensitivity of dielectrometry was improved by separating the effect of sensor external on the measured signal. A new algorithm to obtain the degree of cure during non-isothermal dielectric cure monitoring for glass/polyester and glass/epoxy composites was developed by employing a function of both temperature and dissipation factor, in which five cure monitoring parameters were used to calculate the degree of cure. The decreasing pattern of dissipation factor was compared with the relationships between the degree of cure and the resin viscosity. The developed algorithm might be employed for the non-isothermal in situ cure monitoring of thermosetting resin composites.