A layer tension loss and cure model for filament wound composites

Abstract

The simulation program FWCURE [1] models the curing process and layer tension loss of axisymmetric filament wound composite cases during fabrication. For a specified temperature cure cycle, the model predicts the temperature distribution, resin degree of cure, viscosity, layer compaction, and fiber motion throughout the composite case during cure. The scope of the simulation program developed by Tzeng [1] has been extended, and the modifications to the FWCURE program are the goals of this investigation. Major modifications to FWCORE include a more general 2-D layer tension loss model, additions to an element curvature calculation routine, a new cure reaction kinetics model and viscosity model for a Fiberite-974 epoxy resin system, and modifications and additions to Input/Output (I/O) throughout the program. Modifications and additions to FWCORE are implemented in the analysis of an 18 inch diameter test bottle. Results of the simulation are compared with test data obtained during winding and cure of a graphite-epoxy 18 inch test bottle. Excellent agreement was obtained between the results of the model and data. Another major accomplishment involved coupling FWCURE with a thermo-mechanical stress simulation program called WACSAFE. When combined, the coupled program forms an improved comprehensive structural model which characterizes the thermal, chemical, physical, and mechanical processes occurring during winding and cure of filament wound composite cases. The complete simulation program should provide the process engineer with a resource to help select an optimum fabrication cycle, assess the processing characteristics of new matrix reein eystems, and act as a simulator to yield real time, closed loop process control. FWCURE should also provide information on the processing parameters that have the greatest effect on the final filament wound composite structure.