Thermo-mechanical behavior of epoxy shape memory polymer foams
Thermo-mechanical behavior of epoxy shape memory polymer foams
复制标题
DOI：
10.1088/0964-1726/16/6/037
复制
发表时间：
2007-12-01
影响因子：
4.1
通讯作者：
Campbell, D.
中科院分区：
文献类型：
--
作者：
Di Prima, M. A.;Lesniewski, M.;Campbell, D.
形状记忆聚合物泡沫塑料在生物医学和航空航天领域具有巨大的应用潜力，但其在相关变形条件下的热机械行为还不是很清楚。本文研究了平均相对密度接近20%的环氧形状记忆聚合物泡沫塑料的热机械行为。这些泡沫在不同的应力、应变和温度条件下变形。泡沫的玻璃化转变温度约为90摄氏度，在25至125摄氏度的温度范围内进行压缩和拉伸测试，并使用各种形状恢复测试来测量不同热机械条件下的恢复性能。通过测量拉伸应变随温度的变化，探讨了泡沫材料在温度和应变空间的最大回复极限。进行了压缩试验，以检查材料的可压缩性随温度的变化；这些泡沫可以压实高达80%，并且在多个循环中仍然经历完全应变恢复。此外，拉伸应变到破坏的测试和循环压缩恢复测试都表明，在80℃的温度下变形可以使宏观应变恢复最大化。变形温度高于或低于该最佳值都会导致较低的拉伸破坏应变和循环压缩中不可恢复应变的累积。对不同压缩状态下的泡沫进行微CT扫描，以了解泡沫的变形机理。微观CT研究揭示了细胞的弯曲、屈曲和坍塌随压缩程度的增加，这与已发表的数值模拟结果一致。
Shape memory polymer foams have significant potential in biomedical and aerospace applications, but their thermo-mechanical behavior under relevant deformation conditions is not well understood. In this paper we examine the thermo-mechanical behavior of epoxy shape memory polymer foams with an average relative density of nearly 20%. These foams are deformed under conditions of varying stress, strain, and temperature. The glass transition temperature of the foam was measured to be approximately 90 degrees C and compression and tensile tests were performed at temperatures ranging from 25 to 125 degrees C. Various shape recovery tests were used to measure recovery properties under different thermo-mechanical conditions. Tensile strain to failure was measured as a function of temperature to probe the maximum recovery limits of the foam in both temperature and strain space. Compression tests were performed to examine compressibility of the material as a function of temperature;. these foams can be compacted as much as 80% and still experience full strain recovery over multiple cycles. Furthermore, both tensile strain to failure tests and cyclic compression recovery tests revealed that deforming at a temperature of 80 degrees C maximizes macroscopic strain recovery. Deformation temperatures above or below this optimal value lead to lower failure strains in tension and the accumulation of non-recoverable strains in cyclic compression. Micro-computed tomography (micro-CT) scans of the foam at various compressed states were used to understand foam deformation mechanisms. The micro-CT studies revealed the bending, buckling, and collapse of cells with increasing compression, consistent with results from published numerical simulations.