Colloquia

Summary

Out-of-autoclave (OOA) processing of thermoplastic composites is becoming an increasingly interesting topic in the aerospace industry. Without the need of an autoclave, valuable time and resources can be saved and processing cost can be reduced. Fokker aerostructures is therefore developing the out-of-autoclave mold temperature-controlled (MTC) press consolidation production process in which thermoplastic composites structures can be (co-) consolidated by applying pressure and heat to form the structure into the desired shape and to simulate the autoclave cycle subsequently. However, since this is a novel manufacturing process within Fokker, the process must comply to strict specifications to be qualified and allowed to be used in production. Herein, the qualification must be performed for every material configuration that is desired to be co-consolidated in the OOA MTC press consolidation process.

Currently, Fokker still has a few material configurations that must be qualified before the process can be used in production. In this research two of those material configurations were examined, namely, the (hot) pre-forms and the filler material.

(Hot) pre-forms are pre-pregs stacks heated in an open infra-red oven whereafter it is pressed on a “cold” mold into the desired shape. However, upon co-consolidation (hot) pre-forms are not able to form a proper bond. Therefore, the cause of the poor bonding obtained after co-consolidation was examined. In which the objective was to understand what the effect is of thermal oxidative degradation on the bond quality. Which was examined by the crystallization kinetics, cross-sections and the interlaminar toughness for different (hot) pre-forming exposure times/temperatures and atmospheres (inert/non-inert). Based on the experiments a cause for the decreased bonding was identified and a bond toughness development mechanism for (hot) pre-forms upon co-consolidation was proposed.

Another aspect of the study was the qualification of the filler material to be used in the OOA MTC press consolidation process. The qualification of the filler material was based on the degradation of the material due to the intended heating cycle of the OOA MTC press consolidation process. This was examined by measuring the crystallization kinetics and by performing phased arrayed (PA) scans for various process windows which resulted in a final process window which can be used by Fokker to qualify the filler material for the OOA MTC press consolidation process.