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

Physics-based models are often used to simulate some aspect of the outcome for
candidate cure cycles in coordination with the experimental work. The following paragraphs
discuss useful models for estimating cure, viscosity, and consolidation.
2.4 Temperature and Resin Cure Reactions
The essence of composite processing is the curing reaction of the resin within the
prepreg material. Empirical mathematical models that describe the heat of reaction in relation to
applied heat over time are widely established. One of the seminal research papers was
published in 1982 by Lee, Loos, and Springer (Lee, 1982) for modeling the curing kinetics of
Hercules 3501-6 resin. The ability to model the resin cure behavior is the foundation upon which
other useful models can be built that are dependent on resin state.
Differential scanning calorimetery (DSC) is a commonly used method for measuring the
heat of reaction of a sample in response to temperature changes over time. Both isothermal and
temperature ramp conditions are used to portray cure kinetic behaviors. The relation between
the reaction rate, dα/dt, and the degree of cure, α, where 0 ≤ α ≤ 1 is given by
α
α = ∫ d
d t .
d t
An Arrhenius functional form (for instance, Adams and Goldfarb (Adams, 1982)) can be used to
estimate reaction rate, after fitting the DSC data to the model. This form of reaction rate model,
the “the nth order model”, is given by:
dα
dt
where A, Ea/R and n are material constants.
− a /
= Ae ( 1 − α )
E RT n
Another form, the autocatalytic form, which includes an additional term and constant m, is given
by:
dα
= Ae
dt
− E a / RT
11
n m
( 1 − α ) ( α )
.