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

consolidation submodel with the thermal cure and viscosity submodels. The principal
shortcomings were the following:
(1) The effects of resin viscosity changes on the resin pressure and flow within the
consolidation submodel were not linked to the thermal degree of cure and viscosity
changes.
(2) The soil-based resin flow and consolidation submodel splits the applied pressure between
the solid and fluid components of the soil, determined by the user-specified elastic modulus
value for the soil solid component. The remaining pressure is applied to the resin/pore
pressure. Consolidation increases in porosity (soil) or fiber volume fraction (composite)
were not accompanied by the required nonlinear increase in stiffness that characterizes
composites.
(3) Consolidation changes to fiber volume fraction were not coupled to changes that would
occur in permeability of the laminate material.
(4) The software was not very open, accessible, or transparent so as to allow the user to
customize the model for specific objectives.
A simplified FEM composite model was developed and exercised to explore the
behaviors of pressure application and consolidation. It was constructed of a simple cube (1 m x
1 m by height 1 m) of soil material onto which was applied a rigid surface to simulate the tool lid
imposing pressure downward onto it. The purpose of the simplified model was to investigate
pressure application and its effects on displacement, porosity, and pore pressure for application
to a new model. It was expected that the reduced laminate volume would occur equally with
respect all directions, resulting in a uniform increase in laminate density. The model set-up was
to apply pressure on the top surface to reduce the volume of the laminate, while constraining
the sides and bottom from moving or expanding, to simulate tooling constraints. A pressure film
coefficient was assigned to all nodes on the 4 vertical sides to simulate resin flowing out. The
pressure film was used to reduce pressure incrementally, analogous to Newton’s law of cooling:
Resin pressuret+1 = resin pressuret (1- hp) where hp = film coefficient and hp < 1.0
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