Monitoring deformation mechanism of foam cells in polyethylene foams via optical microscopy: Effect of density and microstructure

Abstract

The effect of cellular microstructure and density of low-density polyethylene (LDPE) foam during the compressive deformation were evaluated. Progressive foam cell structure deformation at crosshead speed of 10 mm/min was closely monitored and captured using a portable digital microscope with the assistance of a proposed coating technique to enhance contrast of the foam cells. Results revealed that higher density foam, LDPE1.0, experienced higher compressive stress than the LDPE0.5 foam. It was believed that thicker cell walls in the LDPE1.0 foam contributed to the foam stiffness and higher stress was required to impose cell bending, buckling, and collapse. It was also discovered that the existence of larger cells within a group or cluster of small cells in the LDPE1.0 foam acted as stress concentration points and initiated the formation of shear bands in the foam cells deformation mechanism. The extent of compressive strain on the foam cells were also investigated, and results showed that cells undergo lower compressive strain compared to the actual deformation level given directly by the machine crosshead. Cells located in the middle section of the foam recorded a strain

Mechanical compaction mechanisms in the input sediments of the Sumatra Subduction Complex- insights from microstructural analysis of cores from IODP Expedition- 362

“…11). In deforming granular foam material, bending was reported as the dominant deformation mechanism for the reduction in porosity and developing preferred alignment of the long axis of pores perpendicular to the applied stress (Elliott et al, 2002, Zhou et al, 2004Samsudin et al, 2017;Zakaria et al, 2018) studies on the experimental deformation of granular foam is described in supplementary data-16). Friction adheres clay particles to the edge of pores while the middle of particles drops into the pore, resulting in bending by intracrystalline slip.…”

Design and Analysis of Electronic Wearables for Taekwondo Sports

“…The shape of the structure influences load transfer during impact, on the other hand, the ability to absorb elastic energy controls rebound [50]. Usually, headgears are made out of closed-cell polymer foams and there and they are usually characterized by their density, Young's modulus and yield stress [51,50]. These foams are commonly used for impact protection and can undergo significant compressive deformation.…”

“…They have excellent energy dissipation properties and are flexible that allows them to be molded in complex helmet shapes [50]. The large deformation these foams are capable of is done by cell bending, cell collapse and cell buckling [51]. To visualize this, we can use a stress-strain curve of typical closed-cell foams and an interesting point is the long plateau seen in Figure 12.…”

Mechanical and flame‐resistance properties of polyurethane‐imide foams with different‐sized expandable graphite

“…[ 1‐3 ] Developing high performance polymeric foams and studying the mechanisms causing higher performance is important. [ 4 ] Commonly used polymeric foams include polyethylene foam, [ 5 ] polyurethane foams, [ 6,7 ] polystyrene foam, [ 8,9 ] polypropylene foam, [ 10 ] and others. [ 11‐13 ] Polyurethane (PU) foams are widespread in many applications, such as facile transport, construction, cold storage, etc.…”