Hybrid-matrix processing: How to co-inject multiple resin systems into one composite part?

Conventional composite structures consist of fiber reinforcement embedded in a single matrix system. Hence, the matrix dominated composite properties are defined for the entire part and the matrix selection represents a compromise between the dominant demands. The Hybrid-Matrix approach aims at the defined integration of multiple matrix materials in one composite structure with an out-of-plane matrix transition. The composite properties can be adapted to locally changing requirements and functionalities. This study presents the development of a closed mold injection process in which different resin systems are co-injected to form defined transition areas and a transition line where resin system merge and co-cure. This Hybrid-Matrix-RTM (HyMa-RTM) process concept is based on the control of the shapes and the reduction of velocities of the flow fronts by local and reversible compaction of the preform. Injection experiments, using a transparent modified RTM tool for flow front analysis are conduct to evaluate the concept of reducing the flow front velocity. The results show that the flow front velocity is reduced by approximately 95%-98% at compacted areas. Based on the proof-of-concept to control the flow front experimental investigations are conducted to define an injection strategy and process parameters for a co-injection process. The results of the co-injection, using colorized resin systems, show the potential of the HyMa-RTM process. A test plate is manufactured fulfilling the requirements regarding tolerances of the transition area and the course of the transition line.