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

Note that while the force is held constant from t=0 until around t=180 minutes, the
pressure on the laminate drops, caused by progressively more contact area between the tool lid
and the laminate. As the resin melts due to heat transfer more resin flows out of the contacted
CVs, and these CV heights are reduced, allowing the lid to contact more top surface area.
4.6 Investigation into Material Property Variation
Variation is a known factor affecting yields of composite parts. For a closed-cavity,
press cure process, it is suspected that variation in per ply thickness, caused by varying
thickness of resin film, along with process variation during the prepregging process. The result
of this difference in bulk is that for a fixed number of plies in a laminate layup, the thicker
regions will vary disproportionately, causing a change in the initial contact patterns between the
tool lid and the laminate top surface. This change is suspected to cause differences in resin
pressure patterns as a result, which may affect the tendency for fiber waviness to occur. For
each flexbeam material, two levels of bulk were applied with the model, 10% and 15%. The
output data for each case was then analyzed.
4.7 Model Output For Cure Process with a Symmetric Laminate and Tool
Before presenting the results for the designed flexbeam and tooling, if the flexbeam
laminate and its tooling were instead symmetrical with respect to length, the expected pressure
distribution would also be expected to be symmetrical. As a check, the laminate and tool
geometry were adapted to be symmetrical. Figure 4.9 illustrates the initial contact positions of
the flexbeam and tool lid.
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