Mechanical response and fracture dynamics of polymeric foams

Heterogeneous materials usually break through a process of microcracking that eventually leads to final rupture after accumulation and coalescence of many microcracks. The statistical properties of microcracking rupture have been known to resemble critical point statistics, with many of the physical quantities obeying power law distributions. However, there is no clear understanding of the origin of these distributions and of the specific values observed for the power law exponents. In this paper, we review the special case of polymeric foams that have the advantage of containing a single material component, the polymer, as opposed to usual heterogeneous materials such as composites. First, we briefly review the typical features of the polymeric foam mechanical response up to rupture that have been widely studied previously. Then, we focus on a less well-known aspect: the rupture dynamics of polymeric foams. We not only show that polymeric foams behave like other heterogeneous materials, i.e. they display power law statistics, but we are also able to test the effect on the power laws of the following properties: the foam heterogeneity by changing its density, the foam mechanical response by changing its temperature and the mechanical history by comparing creep tests and tensile tests.