Development of numerical/experimental technique for measuring of overall behaviour of cellular materials

The project concentrates on establishing an experimental procedure for in situ measurement of sample deformation and underlying micro-deformation of cellular structures. The solid state foaming process, gas diffusion technique, has been thoroughly investigated with respect to processing conditions and resulting microstructure of polycarbonate samples. This allows for repeatable and controllable manufacturing of uniform polymer foams with cell sizes in 1-10 mm range and relative densities in the range of 0.1 to 0.9. It has been observed that the decrease in density with foaming temperature is approximately linear and higher-pressure result in lower foam density. Furthermore, the minimum foaming temperature decreases with increasing gas pressure. The mechanical tests indicate that strain to failure, foam stiffness and linear elastic range increases with foam density. A preliminary in-situ observation of cell wall deformation of commercial PVC foam, though of significantly larger cell size than that of the polycarbonate foams, indicate that strut/wall bending dominates micro-deformation mechanisms. It might not be the case at high foam densities. Financed by Statens Teknisk-Videnskabelige Forskningsråds Rammeprogram Structurally Graded Polymeric Materials.... The project is finished. (Charles Lawrence, Ryszard Pyrz)