泡沫材料的应变率效应

对泡沫材料的应变率敏感性进行了系统深入的讨论,认定这种材料是应变率敏感材料,这种敏感性主要是由于泡孔的变形特性产生的。泡沫材料变形的局部化、微观惯性和致密性导致压垮应力明显提高,基体的应变率效应及泡孔的形状大小并不能对泡沫材料应变率敏感性起主导作用。

Strain rate effect on the properties foam materials

HT5SS]ST5BZ] Improved SH PB method and seim conductive gauges were used to investigate strain rate effec ts on the properties of foam materials. Experiments results involve quasi stati c and dynamic stress strain curves of three densities of rigid fiber polyureth ane foams, four cell sizes aluminum foams of the same density, and four densitie s aluminum alloy foam. All experimental results indicate that strain rate effect on foam materials is evident, although matrix, some of which are strain sensiti ve and some are not, cell sizes and relative density are different. It is the ex isting of cells that cause strain rate effect on foam materials. It can be concl uded that crushing stress will be enhanced under high strain rate because of the following two reasons: (1) as impact velocity increases, the cells near the im pact surface instantly are tightly compressed and therefor strain rate will inc rease and the colliding speed of cell wall will enlarge, causing the crushing st ress to increase; (2) The highly localized nature of crushing results in very large strain rate in crushing band and therefor micro inertia will play a more important role causing crushing stress to increase. Another conclusion is that s train rate sensitivities of matrix and cell morphology themselves are not the ma in reasons for strain rate sensitivities of foam materials.