Fatigue mechanisms of a closed cell elastomeric foam: A mechanical and microstructural study using ex situ X-ray microtomography

Assessment of frequency and amplitude dependence on the cyclic degradation of polyurethane foams

“…Effects of compressive fatigue on the viscoelasticity of elastomeric foams is a burgeoning field of study for tactical protective equipment and has also received some attention for footwear applications. [8][9][10] Fatigue failure in conventional engineering materials is typically defined by abrupt loss of stiffness or catastrophic fracture. 11 This failure mode, however, is not readily observable in elastomeric foams in compression-dominated cyclic loading.…”

“…[36][37][38] For the elastomeric foams used in this study, however, fatigue damage and failure typically does not manifest as discrete macroscale damage to the material, such as delamination or microfracture coalescence. 8,45 In this study, low-rate fatigue experiments monitored with DMA and FTR are used to quantify the changes in viscoelasticity in polyurethane foams under repetitive loading. This technique enabled quantification of changes in viscoelasticity across fatigue cycles for a specimen directly as a measure of stiffness and damping.…”

Unintended consequences: Assessing thermo-mechanical changes in vinyl nitrile foam due to micro-computed X-ray tomographic imaging

“…Example quantities of interest for foams and polymers include feature sizes (voids, particles, ligaments) [ 3 , 4 ], relative density and porosity [ 4 - 7 ], or anisotropy and auxaticity [ 8 , 2 ]. For polymer foam applications, in-situ load frames enable microstructural imaging, stress, and strain measurements, which enable a volumetric assessment of the onset of instabilities, measure materials properties such as the tangent Poisson’s ratio, and apply techniques such as digital volume correlation (DVC) [ 9 , 10 ], typically over the course of several scans [ 11 , 12 , 8 , 13 - 15 ]. For complex or heterogeneous material applications, such as foams used for impact protection [ 16 - 18 ], micro-structural responses to strain are important to modeling the material performance [ 19 , 20 , 11 ].…”