Analysis of thermo-mechanical-chemical properties of GFRP during curing by means of process monitoring and process simulation

Abstract

Inherent process-induced residual stresses and deformations impede the application of composite parts. Process-induced deformations lead to a mismatch of parts to fit and result into additional assembly effort. To counteract the deformations a compensating tooling design needs to be derived. Residual stresses can reduce the strengths and influence the failure behavior. Unknown residual stresses lead to overweight structures resulting from unnecessary high safety factors. For a more efficient process development and optimization, process simulations are increasingly applied. This work deals with a sensor-supported process simulation method. For a deeper process understanding the process strains of a glass fiber reinforced cross-ply are monitored during the curing process. In order to identify different material phases of the thermoset matrix material dielectric cure sensors are employed. In parallel a process simulation using a viscoelastic material model is applied to calculate the process strains, reaction kinetic and the material phases. The obtained sensor data are used to validate the process simulation, to determine points of material transitions as well as the stored residual strain level and to optimize the boundary conditions, e.g. to model the tool-part interaction. A very good qualitative and quantitative correlation between the measured and simulated process strain could be observed after the calibration step.