Modelling and simulation
Modelling and simulation of composite materials is being used extensively in the group for applications ranging from failure mechanism predictions to sensor placement optimisation.
Finite Element Analysis (FEA) tools have been developed for non-linear analysis and complex material models.
Probabilistic design is being used for characterisation of biocomposite materials.
Finite element analysis
Damage initiation and evolution
The evaluation of the initiation and evolution of damage in heterogeneous materials is important to enhance the understanding of mechanical behaviour of complex materials and structures. We have developed a Phantom Node Method (PNM) for the computational modeling of weak and strong discontinuities in heterogeneous materials. By introducing additional degrees of freedom, a discontinuous element is considered as a superposition of two independent continuous elements. Only standard shape functions are used and elemental locality is preserved in a purely displacement based finite element (FE) setting. A cohesive zone concept is applied along the discontinuity surface to incorporate nonlinear fracture. Implemented into the commercial FE software Abaqus as a user-defined subroutine.
Process simulation
Finite element analysis was used to simulate the welding stage of the thermoset composite welding process. This includes, the squeeze flow of the thermoplastic melt out of a joint, the transport of trapped air within the welded interface, and the healing of the thermoplastic/thermoplastic interface. understanding will be achieved through analytical, numerical, and experimental investigations.
Success stories
Aircraft coating lifetime prediction
The service life of many civil and military aircrafts are extended well beyond their original design limits. Hence aircraft corrosion becomes one of the main cost drivers for aircraft maintenance, and aircraft coating systems serve as the first line of defence against corrosion.
A special purpose finite element simulation program has been developed to investigate damage evolution in aircraft coatings. Cohesive cracks within the polymer matrix material are modelled as well as adhesive cracks along the interphase between filler particles and the polymer matrix.
SHM sensor placement optimisation
In Structural Health Monitoring (SHM) systems, sensors are permanently attached to the structure. The system configuration has to fulfil a strong compromise between good coverage of the structure ensuring a high probability of detection and as few sensors as possible. Therefore, an optimization of the sensor placement is required to achieve the best configuration for a given structure. Work is done in the team to propose a system optimization based on a particular imaging technique.
Squeeze flow analysis
UQ Composites has worked on a project that has required FEA modelling of squeeze flows found during the welding of thermoplastic polymers. The project used experimentally measured thermoplastic polymer melt viscosity data to effectively model the real welding scenario. This data was recorded at UQ using AMPAM facilities, leading to the successful modelling of flow behaviour during the welding process, within and out of the welding area. The result of this work has led to the estimation of the spew fillet size, the change in thickness of the welded interface over time, as well as, the effect of elastic adherents on the flow behaviour.