Fiber metal laminates (FMLs) are hybrid materials consisting of alternating layers of metallic sheets and fiber-reinforced polymeric-resin composites. FMLs combine some of the best properties of the metal and the composite parts making them highly attractive for aerospace applications. FMLs are currently being manufactured under elevated temperatures and pressures in a compression press or an autoclave. These fabrication processes are expensive and the part size is limited by the size of the press or autoclave. NASA Langley Research Center has developed a process which can be used to manufacture FMLs by the cost effective Vacuum Assisted Resin transfer Molding (VARTM) process. The objective of this study was to investigate the manufacturability of the FMLs using low cost liquid composite molding techniques but with the same level of quality of FMLs fabricated in an autoclave.A flow visualization fixture of the VARTM/FML process was constructed and used to observe the resin infiltration process. The results of the flow visualization experiments were analyzed and compared with the predictions of a VARTM process simulation model. The simulation model of the hybrid preform structure of the FMLs was developed using the commercial software package FLUENT. The model used a transient two phase volume of fluid (VOF) method to track the resin progression. The model was used to predict the resin flow patterns and infiltration times of the hybrid FML structure during the resin infusion stage of the VARTM process. A variation of the VARTM process, the Controlled Atmospheric Pressure Resin Infusion (CAPRI) process, was also considered. Compaction and permeability characterization studies were performed for the preform materials used in the FML structures under different testing conditions. The pressure vs. fiber volume fraction data was fit to mathematical models. Similarly, the permeabilities in the principal material directions were measured and the fiber volume fraction vs. permeability data was fit to mathematical models. The mathematical models were used to determine the input parameters of the simulation model such as initial volume fraction, permeability and the model constants for a developed user defined compaction model. Parametric studies were performed with the simulation model to explore the effects of various model inputs on the flow patterns of the FML structures. An attempt was made to further improve the model by the integration of a compaction model that could dynamically update the permeability and thickness of the preform with time. The flow patterns and the infiltration times predicted by the simulation model agreed very well with the flow patterns and times recorded during the infiltration and manufacture of an actual FML panel. The results of this study showed that FML parts can be successfully infiltrated when flow pathways were included in the hybrid preform structure. Thus, this study demonstrates the manufacturability of high quality FML parts using the VARTM and CAPRI processes.
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