Abstract

Abstract

This work describes a computational strategy, based on a stabilised finite element method, to simulate bifluid flow with capillary effects in a fibrous microstructure. In this framework, triple junction equilibrium is imposed as a natural condition in the weak formulation of the Stokes problem. Two types of 2D microstructures are then considered, hexagonal and random, and studied in terms of numerical permeability and capillary pressure.

Abstract

In this study, resin permeability of plain-woven composites is analyzed using a three-scale homogenization method. To this end, the three-scale homogenization method is developed to analyze the resin flow through both the structures of fiber bundles and the inside of fiber bundles, and also the mesoscopic and macroscopic resin permeability. To evaluate the validity of this method, resin permeability and characteristic flow velocity of plain-woven glass fiber-reinforced plastic (GFRP) are analyzed. The results show that the present method successfully analyzes the resin permeability of plain-woven composites.

Abstract

Compression resin transfer moulding (CRTM) can help to reduce costs and increase the productivity of composite parts in the automotive industry. This process is suited for fast production of high quality parts, but a number of parameters must be precisely characterised and well controlled during the process. This work describes the CRTM manufacturing process of a real sports car bonnet. Resin and carbon fibre reinforcement have been characterised (viscosity, permeability), and this information has been used to perform numerical simulations to optimise the process parameters in order to reduce the cycle time. The heating cycle has also been optimised and the possible implementation of an induction heating system has been analysed. Once the process parameters have been defined, the mould has been manufactured and bonnet prototypes have been manufactured. This work has been carried out within the framework of the project ADVANCRTM.

Abstract

Hydrophobic treatment of cement pastes is most effective way to resist the penetration of water with aggressive ions to improve durability of cement-based materials. In this paper, the mechanism of carboxylic acid ammonium salt integral additionon hydrophobicity of cement-based materials is analyzed. The effects of carboxylic acid ammonium salt on hydrophobicity, moisture diffusion and hydration products are investigated by experimental methods.The results of water vapor sorption isotherm show that the addition of carboxylic acid ammonium salt increases the pore volume. The simplified analytical hydrodynamic model of cone type pore and Young’s relationship is proposed to analyze the relation between characteristic parameters of pore and the permeability of cementitious materials. It can be concluded that the hydrophobicity results from the change of pore structure and the hydrophobic surface of cone region. These results provide the guidance to design the durability and develop the new hydrophobic agent used in cementitious material.