Process Modelling of Polymer-Derived Composites using a Multiscale Framework
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Gregory ODEGARD (UNITED STATES), Marianna MAIARU (UNITED STATES)Abstract :
During the processing of high-performance thermoset polymer matrix composites, chemical reactions occur during elevated pressure and temperature cycles, causing the constituent monomers to crosslink and form a molecular network that gradually can sustain stress. As the crosslinking process progresses, the material naturally experiences a gradual shrinkage due to the increase in covalent bonds in the network, causing the formation of residual stresses. Once the cured composite completes the cure cycle and is brought to room temperature, the thermal expansion mismatch of the fibers and matrix cause additional residual stresses to form. These compounded residual stresses can compromise the mechanical integrity of the composite material. Computational process modelling needs to be utilized to optimize processing parameters to reduce residual stresses and increase the composite material durability.
Computational process modeling is greatly complicated by the multiscale nature of the composite material. At the molecular level, the degree of cure controls the local shrinkage and thermal-mechanical properties of the thermoset. At the microscopic level, the local fiber architecture and packing affect the magnitudes and locations of residual stress concentrations. At the macroscopic level, the layup sequence controls the nature of crack initiation and propagation due to residual stresses.
The goal of this research is to use molecular dynamics (MD) and finite element analysis (FEA) to predict the residual stresses in composite laminates and optimize processing parameters to minimize the residual stress. MD is used to predict the polymer shrinkage and thermomechanical properties as a function of degree of cure. This information is used as input into FEA to predict the residual stresses on the microscopic level resulting from the complete cure process. FEA is subsequently used to predict residual deformations and performance of composite structures for aerospace applications. Experimental characterization is used to validate the computational modelling.
Computational process modeling is greatly complicated by the multiscale nature of the composite material. At the molecular level, the degree of cure controls the local shrinkage and thermal-mechanical properties of the thermoset. At the microscopic level, the local fiber architecture and packing affect the magnitudes and locations of residual stress concentrations. At the macroscopic level, the layup sequence controls the nature of crack initiation and propagation due to residual stresses.
The goal of this research is to use molecular dynamics (MD) and finite element analysis (FEA) to predict the residual stresses in composite laminates and optimize processing parameters to minimize the residual stress. MD is used to predict the polymer shrinkage and thermomechanical properties as a function of degree of cure. This information is used as input into FEA to predict the residual stresses on the microscopic level resulting from the complete cure process. FEA is subsequently used to predict residual deformations and performance of composite structures for aerospace applications. Experimental characterization is used to validate the computational modelling.