Mechanical response and fracture dynamics of polymeric foams

Abstract

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 review briefly the typical features of the polymeric foam mechanical response up to rupture that have been studied a lot previously. Then, we focus on a less-well-known aspect: the rupture dynamics of polymeric foams. We show that not only polymeric foams behave like other heterogeneous materials, i.e. they display power law statistics, but also, we are 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.

Sensing strain and damage in polyurethane/MWCNT nano-composite foams using electrical measurements

“…Each reflects different micro-structural compliance and failure mechanisms. [36,[38][39][40] As already mentioned, the first stage is the linearelastic response of the foam. During this stage, a number of deformation mechanisms occurs with the more dominant ones being the cell wall bending in combination with the compression of the gas contained within the closed foam cells.…”

“…MWCNT produced by catalyzed CVD were supplied by Arkema (France). According to the manufacturer, their diameters were 10-15 nm and they were more than 500 nm long, resulting in an aspect ratio (AR) in the range of [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. Previous studies [19,31,32] utilizing the same batch of CNTs showed good mechanical and electrical results for polymer composites.…”

“…The mechanisms associated with the yielding/collapse plateau, vary depending on the properties of the cell-walls. For rigid foams, macroscopic plastic yielding in the micro-structure is related to fracture of the walls due to buckling failure [39]. In compression, the failure behaviour of low-density foams is dominated by the early collapse of large porous cells which triggers macroscopic fracture of the specimen, whereas high-density foams exhibit more uniform deformation, which results in ductile-like fracture mode under quasi-static loading [41].…”

Creep failure of honeycombs made by rapid prototyping

“…It remains to specify f ε P in Eq. (5). A curve-fitting procedure is carried out on the measured σ versus ε P data excluding the initial peak and the subsequent softening characteristics of Fig.…”

Influence of chemical nature, expansion ratio and cellular morphology on the fracture behaviour of flexible polyolefin-based foams assessed by the Essential Work of Fracture (EWF)

“…Most of rigid polymer foams show linear-elastic behaviour under tension, and hence their fracture analysis may be treated using the concept of linear-elastic fracture mechanics (LEFM) [4][5][6][7][8]. Nevertheless, this linear-elastic approach is not applicable to flexible polymer foams, as in the case of films or thin sheets of polyolefin foams, as a significant extent of plasticity is developed.…”