Abstract

This study aims to modify and characterize an open-cell polyurethane foam with a density of ∼28.7 kg/m³ to study the mechanical behavior in static compression and cyclic fatigue. A technique is presented for transforming this type of foam from a conventional state with a positive Poisson's ratio to an auxetic transformed state with a negative Poisson's ratio (density of ∼119.59 kg/m³) via a specially designed device. The results obtained show the degree of influence of the transformation on the mechanical behavior of this type of foam. The cyclic fatigue tests of auxetic foam were carried out under control-displacement for different loading (r) levels (0.725, 0.75, 0.80, 0.85, 0.90 and 0.95). The monitoring of cyclic fatigue damage of auxetic samples allowed tracing the evolution of the stiffness degradation (F/F₀) as a function of the number of cycles N taking place in two different phases. The hysteresis loops of the different r levels were identified as a function of the number of cycles. The evaluation of the dissipated energy (E_d) and damping (η) as a function of N was also carried out. The results show that the maximum forces involved between 28 N and 580 N are considerably higher than those previously found in the literature. This leads to a significant dependence of the hysteresis loops, E_d and η of the auxetic foam as a function of the number of cycles and the loading rate, with a remarkable stiffness performance compared to other auxetic foams.

摘要

^{本研究旨在对密度为 ∼28.7 kg/m 3}的开孔聚氨酯泡沫进行改性和表征，以研究其在静态压缩和循环疲劳中的力学行为。提出了一种技术，用于通过专门设计的设备将这种类型的泡沫从具有正泊松比的常规状态转变为具有负泊松比（密度为 ∼119.59 kg/m ^{3 ）的拉胀转变状态。}获得的结果显示了转变对这种泡沫的机械行为的影响程度。拉胀泡沫的循环疲劳试验是在控制位移下针对不同载荷进行的（r) 水平（0.725、0.75、0.80、0.85、0.90 和 0.95）。拉胀样品循环疲劳损伤的监测允许跟踪刚度退化 ( F/F ₀ ) 的演变，作为在两个不同阶段发生的循环次数N的函数。不同 r 水平的滞后回线被确定为循环次数的函数。还对作为 N 函数的耗散能量 ( E _d ) 和阻尼 ( η ) 进行了评估。结果表明，涉及的最大力介于 28 N 和 580 N 之间，远高于先前在文献中发现的力。这导致磁滞回线E _d和拉胀泡沫的η作为循环次数和加载速率的函数，与其他拉胀泡沫相比具有显着的刚度性能。