Cushioning performance of flexible polyurethane foams

Abstract

Impact cushioning and deformation of flexible open‐cell polyester polyurethane (PU) foams were studied as a function of specimen geometry, including the incorporation of controlled voids. It was shown that cushioning behavior is dependent on sample geometry, which was in trun due to a complex balance of air compression and air flow, which changes with surface area‐to‐volume ratio of the impact specimen. Deformation studies show that impact compression proceeded initially by crushing the surface layers with little or no deformation of the center layers. As bulk compression was increased, deformation progressively propagated for the collapsed layers tending to a more uniform strain distribution at high bulk compression strains. Local asymmetric strain patterns were exaggerated using square cushions, because of cornr effects which complicated air flow paths. It was concluded that cushion curve determination of open‐cell foams would be more accurately performed using circular samples and deflecting air pressure form the top surface of the cushion to more closely simulate practical conditions. When designing at or near the margin, the number of cushions should be kept to a minimum and open surface area to volume ratios minimized by adopting square rather than strip cushions.

Cushioning energy absorption of composite layered structures including paper corrugation, paper honeycomb and expandable polyethylene

“…In addition, Yu et al 19 found that the impact rate had a significant effect on the energy absorbing property and local deformation mode of aluminum alloy honeycomb. Sims and Bennett, 20 Zhang et al, 21 and Landro et al 22 studied the static and dynamic compression property and cushioning energy absorption of plastic foams expandable polyethylene (EPE), expandable polystyrene (EPS), expanded polypropylene (EPP) and expandable polyurethane (EPU) and showed that the strain rate of porous foam had little effect on the compressive strength. Bouix et al 23 investigated the compressive stress and strain behavior of EPP at different strain rates in order to demonstrate the effects of foam density and strain rate on the initial collapse stress and the hardening modulus in the post-yielding plateau region.…”

Cushioning capability analysis of seat foundations considering the sitter’s anthropometric dimensions

“…The reproduction of service loads and ergonomics are significantly important in terms of the success of the performance tests for humans in relation to different types of seats (Lee and Ferraiuolo 1993;Li 2017). The development of realistic performance tests has been extensively studied in order to investigate the load-deformation behavior of vehicle seats, pilot seats, and wheelchairs (Sprigle et al 1990a,b;Shen and Vertiz 1997;Sims and Bennett 1998;Smardzewski et al 2010;Kim et al 2014;Li 2017;Hu et al 2016;Li et al 2017Li et al , 2018Demirel and Tuna 2019a,b) Several researchers with an interest in seat applications changed the geometries of the PU foam and indenter by using ASTM standard D3574-17 (2017). Sims and Bennett (1998) found that the geometry of the PU foam was an important factor in terms of its loaddeformation behavior.…”

Effects of chain extender in biodegradable polyurethane foams

“…Flexible polyurethane (PU) foams have the largest production volume among the various types of PU product [1,2]. Most molded foams are used in transportation seating and trim parts, packaging, furniture and novelty items.…”