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

maximum at x=0. Resin flow will then occur as a result of the differential pressure, moving from
the higher resin pressure to lower. The result will be a reduced laminate resin volume, a
Resin flow
Figure 3.2. Consolidation of a Flat Laminate with Pressure Applied by a Rigid Surface.
displacement change for the top surface and a reduced overall laminate volume. Here it is
assumed that the predominant fiber orientation for the laminate is along its length; therefore in
reference to the figure, the predominant resin flows will be horizontal, flowing out the edges on
either side.
by Darcy’s Law:
The velocity of a fluid through a porous media of unit cross-sectional area is governed
Resin flow velocity =
28
K dPr
µ L
where the differential resin pressure dPr (Pa) exists between 2 points separated by a distance L
(m), K is the permeability (m 2 ), and µ is fluid viscosity (Pa-sec). For application to flow through a
composite laminate, all laminate volume is assumed to consist of fibers fully saturated with
resin, with negligible void volume. Note that permeability can be thought of as a proportionality
constant that accounts for the pressure drop through the laminate under conditions of a
constant flow rate.
3.6 Permeability
Permeability is a fundamental material property for resin flow characteristics through a
laminate. Gutowski proposed an expression for permeability based on the Carman-Kozeny
constant kii:
Applied pressure
Laminate
X = -L/2 X=0 X = L/2
L
Resin flow