Predicting Stress Development and Incomplete Conversion in Thick Thermoset Tooling Runs
Predicting cure exotherms and volumetric shrinkage gradients prevents matrix cracking, low core conversion, and dimensional distortion in thick thermoset tools.
Exotherm Prediction
Meaning
Numerical simulation of the heat generated during the polymerization reaction of a thermosetting resin allows for the prevention of thermal damage during manufacturing. Applying exotherm prediction during the tool design stage assists engineers in mapping out the thermal profiles across different part thicknesses. This method avoids the costly trial and error approach during process development.
Thermal Simulation
Finite element analysis combines cure kinetics with transient heat transfer equations to model the curing process. The simulation calculates how much heat is released as the polymer cures and how quickly that heat escapes through the mold walls. These calculations determine the temperature distribution within the curing part.
Overheating Hazard
Thick composite structures are highly insulated by the carbon or glass fibers, preventing reaction heat from escaping. When the internal heat generation exceeds the rate of heat dissipation, the temperature rises rapidly. Accurate exotherm prediction identifies these hot spots before the physical tool is built, preventing matrix degradation or fire during curing.
Process Optimization
Validating the prediction model on prototype parts using embedded thermocouples ensures that the heating rates are safe for production. The resulting heating cycle uses specific dwelling periods to slow down the reaction rate during peak heat generation. This careful planning maximizes production yield and allows for the safe processing of complex geometries that would otherwise fail under standard cure cycles.