In this study the foaming dynamics and cell microstructure of polystyrene (PS) and polystyrene/nanosilica nanocomposites containing n-pentane foaming agent were investigated. In order to evaluate the nucleation and growth of bubbles in samples, in-situ microscopic observation method was used, and their foaming process in a discontinuous system was investigated. Nanocomposites were prepared by solution mixing method and their rheological properties were determined by rheological test. The contact angle method was used surface tension measurements. Incorporating of nanosilica into PS matrix decreased the contact angle and increased the surface tension of the samples. In order to investigate the foaming dynamics of samples, sheets with thickness of 200 μ m were saturated in a high temperature and pressure chamber. Foaming dynamics was studied by the designed system. The temperature effect on the foaming dynamics was investigated in the samples containing of 3 %wt. n-pentane. Although the nucleation and growth rate of bubbles with temperature increasing from 140 to 160 º C has almost been doubled, but broader cell size distribution was observed. In nanocomposite samples the nucleation has been increased compared to polystyrene, and the onset of nucleation has been dropped. By increasing n-pentane content to 5 %wt., the nucleation in nanocomposite samples was significantly increased compared to polystyrene. For further investigation of the final microstructure of foams, scanning electron microscopy (SEM) images were prepared and the results showed that silica nanoparticles have generated more uniform cells in the final microstructure.

During the foaming process of polyurethane, the surfactant plays a significant role in stabilizing and setting the foam. Simulation this role helps in better predicting the final performance and optimum foam formulation. The relation between the amount of surfactant added to the formulation and the surface tension was studied experimentally by using the capillary rise method to develop a simulation model. This model was aimed to study the critical role of the mechanism that surfactants have in the initial stages of gel formation and through the point where viscosity is high enough to create resistance to support the foams. Bubble sizes were calculated based on the number of nucleation sites, gas generation rate, surface tension, and inner bubble pressure. Since important properties of polyurethane foam, such as compressive strength, closed-cell content, and thermal conductivity can be related to the bubble sizes, this model can be used to predict foam performance and to develop new foam formulations.

In this study, the rupture criterion of bubbles wall in Aluminum metal foam liquid was investigated at the first stage, using Lattice Boltzmann. The two phases modeling were accomplished by using a modified Shan-Chen model. This model was run for several bubbles in A356+3wt.%SiC melt system. Then, bubbles morphologies (virtual metallographic) for A356+3wt.%SiC foams were simulated. Results showed that simulation data and the virtual metallographic have a good agreement with the metallographic empirical results after solidification. In the second stage, several cubic A356+3wt.%SiC foams were compressed under uni-axial compression load based on ASTM E9 standard. Stress-strain curves of foams were determined by a data acquisition system gaining 10 samples per second. Foams plastic deformation behavior then was simulated based on a new asymptotic function using ABAQUS software. Discretized digital solid-model of the solid bubbles was prepared with virtual metallographic images which obtained from the present code. The load-displacement curves were then plotted for simulation and experimental results. Results show that both curves which were obtained from experimental and simulation have a good agreement with approximately 1.8% error. Therefore, the present software could be a useful tool for predicting the metal foams plastic deformation behavior without any experimental try and error.

Polymeric foams have a cellular structure composed of a polymeric matrix with gaseous cells which are achieved by expansion of a blowing agent in polymer melt matrix during a foaming process. In the present study, the bubble expansion step in Polystyrene/CO2 batch foaming process was simulated and compared to the reported experimental results. A single spherical bubble surrounded by an incompressible viscoelastic fluid (upper-convected Maxwell model) was considered. To calculate concentration profile in the shell, mass diffusion equations were solved using finite element method, potential function definition and integral methods. The predicted results show that when the gas concentration profile obtained by finite element method and the concentration gradient near the bubble shell interface were used to calculate the pressure inside the bubble, the predicted results were in good agreement with the experimental ones as there was less than 1% error at each foaming time. The effects of the thermo-physical and rheological properties on the bubble growth dynamics were also studied and it was found that increasing the diffusivity coefficient by a factor of 10 would increase the bubble size up to 1.5 times, whereas increasing the viscosity by 3-fold would only change the bubble size about 2%, which shows that the bubble growth step in foaming process was a mass transfer controlled process.