Phenomenological Analysis of Thermo-Mechanical-Chemical Properties of GFRP during Curing by Means of Sensor Supported Process Simulation

Robert Hein,Robert Prussak,Jochen Schmidt

doi:10.3390/pr8020192

Abstract

Inherent process-induced deformations (PID) and residual stresses impede the application of composite parts. PID lead to a geometrical mismatch in assemblies and require subsequent work for tolerance compensation. Unknown residual stresses cause overweighted structures resulting from unnecessary high safety factors. To counteract the deformations, the tool design needs to be modified until the component geometry meets the specifications. This process is mostly carried out empirically and is time and cost intensive. To improve the efficiency of the development process, an in-deep comprehension of the manufacturing processes is mandatory. Therefore, experimental and simulation-based methods are increasingly applied and enhanced. The object of this work is to investigate the development of process-induced strains as well as the material behaviour during the manufacturing for a GFRP plate. The process-induced strains are monitored by optical fiber Bragg grating (FBG) sensors. The change of the material phases is detected by dielectric sensors. Furthermore, a detailed process simulation considering viscoelastic effects and reaction kinetics is performed. Finally, the measurements are correlated with the simulation data to validate the simulation approach. A very good correlation for both the reaction kinetics as well as the process-induced strains is observed.

Highlights

Fibre-reinforced plastics (FRP) are increasingly applied for weight savings due to their high weight-specific stiffness and strength ratio
During manufacturing small specimens for DSC analysis are extracted after 90 min and 1300 min before post-cure
The measured glass transition temperature correlates with 50 ◦C with the predicted value

Summary

Introduction

Fibre-reinforced plastics (FRP) are increasingly applied for weight savings due to their high weight-specific stiffness and strength ratio. The main advantages are simple tooling geometries and low process risks [1]. The manufacturing costs are quite high due to the cost-intensive joining and assembling processes. A differential design is not a fiber-oriented design and the high potential of the material is not utilized. Using an integral design approach a fiber-oriented design can be achieved at reduced manufacturing costs. Such an approach leads to a higher process risk. Inherent process-induced residual stresses and resulting deformations occur. They occur due to different thermal and mechanical properties of the fiber and matrix material as well as due to different material orientations of adjacent

Methods

Results

Conclusion