Abstract
In this study, we fabricated poly (methyl methacrylate) (PMMA) microcellular foams featuring tunable cellular structures and porosity, through adjusting the supercritical CO2 foaming conditions. Experimental testing and finite element model (FEM) simulations were conducted to systematically elucidate the influence of the foaming parameters and structure on compressive properties of the foam. The correlation between the cellular structure and mechanical properties was acquired by separating the effects of the cell size and foam porosity. It was found that cell size reduction contributes to improved mechanical properties, which can be attributed to the dispersion of stress and decreasing stress concentration.
Highlights
Foam materials or cellular structure materials are ubiquitous in nature, such as in plants, porcupine quills, bird beaks and feathers; these materials are beneficial for reducing the weight of a structure, and are resistant to flexural and torsional tractions [1,2]
The results show that the compressive elastic modulus and fracture toughness of carbon foams were insensitive to the variation in the cell size at the same foam porosity, while the crushing and bending strength change inversely with the changing cell size
The results show that foams with average cell sizes of 10 mm and 100 mm show a similar modulus at the same density; these researchers concluded that the cell size has a negligible influence on the elastic modulus of the foams
Summary
Foam materials or cellular structure materials are ubiquitous in nature, such as in plants, porcupine quills, bird beaks and feathers; these materials are beneficial for reducing the weight of a structure, and are resistant to flexural and torsional tractions [1,2]. Weller [20] investigated the effect of the cell size on the tensile behavior of high relative density or low porosity microcellular polycarbonate foams, and concluded that the tensile modulus, tensile strength, elongation to break, and the toughness, were not affected by the average cell size within the range from 4 to 40 μm. The supercritical fluid foaming method is regarded as the most convenient way to synthesize microcellular foam This method may be the most likely way to regulate the foam density and the cellular architecture, as it has fewer procedures, and the foaming agents have a small effect on the “parent” material compared with traditional mechanical and chemical foaming methods. Wang [16] studied the dependence of mechanical properties on the cellular structure of the PMMA foams by independently analyzing the effects of the cell size and the void fraction. A numerical analysis based on the FEM was adopted to further demonstrate the experimental results and failure mechanism
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