Effects of cell-wall instability and local failure on the response of closed-cell polymeric foams subjected to dynamic loading

Dynamic deformation response of closed-cell rigid polymeric form is explored at different length scales. This study is facilitated by ultra-high speed photography in conjunction with digital image correlation (DIC). In-plane strain components developed over cell-walls are measured via DIC and compared with the global deformation response of the material. Local strain rates measured at mesoscopic scale are found to be at least one order of magnitude greater than the global strain rates applied on the specimen. Such substantial variation across different scales is used to explain the contribution of the strength and modulus of parent polymer material in the cellular scale deformation and failure response of the specimen, as well as load bearing and strong strain rate sensitivity of the foam. Experimental results are also used in conjunction with idealized models to identify the dominant cellular scale failure mechanisms in the examined material.