A Micromechanics Based Processing Model for the Curing Response of a Unidirectional Fiber Reinforced Composite

Abstract

A micromechanics based thermal model was developed to predict the temperature and degree of cure (DOC) distribution inside a unidirectional fiber reinforced composite during the curing process. Using the concentric cylinder assemblage (CCA) model as a representation of the composite microstructure, the effective thermodynamic properties of the composite were computed based on the fiber and matrix properties through closed-form expressions. By incorporating the cure kinetics of epoxy as the heat generation term in the thermal analysis, the temperature field of the homogenized composite model was solved based on the prescribed cure cycle at the boundary. Meanwhile, this micromechanics model was implemented at the integration point of the homogenized model to predict the local temperature and DOC fields at the microscopic (fiber–matrix) level. Since the heat flux at the axial direction is negligible, this axisymmetric CCA model can be further reduced to 1D heat transfer problem, which can be efficiently solved through the finite difference method. The proposed homogenization scheme and the 1D heat transfer model were validated through a full 3D finite element model. This study suggests that the curing response is influenced by the size of the composite under the same cure cycle.