The resin film infusion process has been identified as a cost-effective fabrication technique for producing damage tolerant textile composites. Dry textile preforms are resin impregnated, consolidated and cured in a single step eliminating costly prepreg tape manufacture and ply-by-ply layup. The large number of material properties and processing parameters that must be specified and controlled during resin infiltration and cure of textile composites make trial-and-error procedures of determining the processing cycle extremely inefficient. Analytical and numerical models are clearly far superior alternatives for determination of optimum processing cycles.
It is the objective of this investigation to develop a comprehensive three-dimensional process simulation model for complex composite geometries and to optimize the RFI fabrication of aircraft stiffened wing structures. This effort will directly impact the process cycle development in the NASA Advanced Composite Technology (ACT) program. A joint research program between NASA Langley, Virginia Polytechnic Institute and State University, The College of William and Mary, Northrop Corporation, and Douglas Aircraft Company is now underway to develop a science-based understanding of the RFI process. The ultimate goal of this program is to develop a comprehensive three-dimensional RFI model for complex shaped composite structures and to incorporate the model into an intelligent process control system which uses frequency dependent electromagnetic sensing (FDEMS) for sensing the process variables in real time. The use of this program will result in new low-cost manufacturing methods for damage tolerant composite aircraft structures.
We used two tests to verify the three-dimensional RFI process model. A tapered single blade stiffened panel and a panel containing a stiffener runout into a front spar were simulated using the three-dimensional RFI process model. The complex shaped stitched preform sections was infiltrated in an instrumented mold. Instrumentation consists of thermocouples, pressure gages, and (FDEMS) dielectric sensors. Comparisons are made between the predicted and experimental flow front, temperature and pressure distributions as a function of time.
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