posted on 2024-10-31, 07:13authored byZhuoting Chen, Behrad Koohbor, Xiang Zhang, Leon M. Dean, Philippe H. Geubelle, Nancy R. Sottos
Frontal polymerization (FP) has emerged as a rapid and
energy-efficient
process for fabricating thermoset polymers and composites. In this
process, a self-propagating reaction front cures the polymer rapidly
by the exothermic heat of polymerization reaction instead of an external
heat source. Design for FP-based manufacturing in commercial applications
requires more comprehensive characterization and prediction of material
evolution and residual deformation throughout the process. Here, we
report experimental and numerical studies in response to this need.
The experimental study focuses on measuring the temperature and cure-dependent
properties of mono/poly dicyclopentadiene to capture the strain evolution
during the frontal polymerization process. The experimentally measured
elastic moduli, Poisson’s ratios, and coefficients of thermal
expansion and chemical shrinkage show strong dependence on the degree
of cure. Based on the experimental output, a coupled thermo–chemo–mechanical
model has been developed to capture the measured residual strains.
The chemical shrinkage is closely related to the curing rate, leading
to strong localization of residual strains in accelerated reaction
regions, especially where two fronts merge. Preheating of the monomer
(or gel) at the fronts merging area is suggested as an effective method
to mitigate residual deformations.