TOOLED THICK COMPOSITES by ARVEN H. SAUNDERS III ...

CHAPTER 3
THE CONSOLIDATION-RESIN FLOW MODEL
3.1 The Cure Process Model
The basis for optimization of a cure process was selected to be a representative
rotorcraft thick composite part with its associated closed-cavity tooling for curing in a bond
press. A flexbeam was selected as a representative composite laminate, to be modeled utilizing
two representative material systems, IM7/3501-6 graphite/epoxy and S2/8552 glass/epoxy. A
generic flexbeam was designed, 6 feet long and 2” thick at one end and 1” thick at the other
end, with its closed-cavity press tooling.
The original plan was to run iterations of a commercial finite element model (FEM) of
the flexbeam as the basis for cure process optimization. The data for the generic flexbeam and
its closed cavity press tooling were input into the software to create a 3-dimensional model.
Figure 3.1 displays the FEM of the generic flexbeam with its tooling. Notice that the laminate is
enclosed within the tool cavity, with the matching tool lid on top. The lid has an inside surface
that directly contacts the laminate and constrains its dimensions and contours. The model was
comprised of a pressure-driven consolidation submodel, and a thermally-determined cure and
viscosity submodel. The soil material element of the of the FEM software, a porous media
having solid and fluid components, was to be used to simulate the consolidation of the laminate
due to pressure application. This approach has been used with some success in modeling a
composite part, since it also consists of fluid (the resin) and solid (the fibers). When the soil
material is consolidated, changes occur in the 3 variables that characterize consolidation:
laminate volume is reduced through displacement changes to increase density, porosity is
reduced, and pore pressure increases. Displacement refers to changes in the height of the
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