Dr Raj Das (Keynote speaker)
RMIT University, Australia

Speech of Titel:Micro-mechanical Modelling of Closed-cell Foams: Effect of Microstructural Variability on the Mechanical Properties of Polymeric Foams

Abstract:Polymeric closed-cell foams are increasingly used as the cores of sandwich structures in the marine, railway and wind power industries. The mechanical behaviour of polymeric closed-cell foams is critical for the integrity of structures. This research aims to develop and validate foam micro-models incorporating microstructural variability and investigate how the microstructural variability affects the macroscopic mechanical behaviour of closed-cell foams. It involves micro-mechanical modelling using the finite element method, imaging techniques and image analysis for realistic foam microstructure characterisation. This was followed by numerical and experimental testing for prediction and validation of foam mechanical properties. Results show that the stiffnesses and strengths of closed-cell foams decrease with increasing cell size and cell wall thickness variations. The strengths are more sensitive to the variations compared to the stiffnesses, and the compressive strength is more sensitive than the shear strength. The compressive stiffness and strength is dependent on cell shape, while the shear stiffness and strength is independent of cell shape. Cell wall buckling followed by material yielding is also observed. This research provides useful information for manufacturers to improve the mechanical properties of structural foams, and for researchers to develop constitutive relations and failure envelops for closed-cell foams



Miss Ada Pui Yan HUNG(Invited speaker)

Swinburne University of Technology, Australia

Speech of Titel:Tensile Properties of Carbon Fiber Reinforced Polymer Composites Strengthened by Graphene Oxide at Cryogenic Temperature

Abstract:Carbon fibre reinforced polymers (CFRPs) have become an ideal structural material for high-performance engineering applications due to their excellent mechanical and thermal properties with high specific strength to weight and stiffness to weight ratios. CFRPs are used in a wide variety of cryogenic applications because of their unique and highly tailorable properties, as well as low coefficient of thermal expansion, which may help enhance the dimensional stability of structures. They are commonly utilized in aerospace and aircraft engineering industries for structures serviced at temperature down to 77K. However, the brittleness and poor crack growth resistance of epoxy restrict the applications of CFRPs, especially under the cryogenic thermal cycling loading environment.
Two competing effects on composite’s stiffness at cryogenic temperature are considered. An increase in stiffness is a constructive effect because the epoxy would be harder at low temperature. Due to the positive coefficient of thermal expansion (CTE) of epoxy, the thermal shrinkage of epoxy would increase the clamping force onto the surface of carbon fiber. A destructive effect is that the thermally-induced stress would generate micro-cracks in the matrix, which would reduce the overall stiffness of CFRPs.
Graphene oxide (GO) is a novel material that possesses high levels of strength and stiffness, which is a promising nano-structural filler to prohibit crack propagation inside a polymer-based composite. Its negative CTE improves the cryogenic mechanical properties of CFRPs. Experimental results showed that the introduction of GO into CFRPs could improve the fibre/matrix interfacial adhesion and stress transfer at cryogenic temperature. The underlying mechanisms of the enhancement by GO in CFRPs at room and cryogenic temperatures are explained in terms of CTE.