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Cold programming of epoxy-based shape memory polymer
Structures ( IF 4.1 ) Pub Date : 2020-07-06 , DOI: 10.1016/j.istruc.2020.05.023
Kartikey Shahi , R. Boomurugan , R. Velmurugan

Shape Memory Polymers (SMPs) are the class of smart materials that show ability to memorize different shapes and regain original shape. The conventional method is to heat SMP above its glass transition temperature (Tg) and deform it to obtain the desired shape. It reverts to original shape upon heating. This is known as hot programming. Recent advances in the programming of SMP have shown promising results of a new programming method also known as cold programming. The SMP is plastically deformed at a temperature below Tg to impart the desired shape. This paper aims at the experimental investigation of shape memory properties of Epoxy-based SMPs using the cold programming method. The polymers of Epoxy used in this work are Diglycidyl Ether of Bisphenol-A (DGEBA) and Neopentyl Glycol Diglycidyl Ether (NGDE). The mechanical properties like elastic modulus, tensile strength, and failure strain have been found for different ratios of DGEBA and NGDE at various temperatures. The Tg of different compositions has been measured using Differential Scanning Calorimetry (DSC). In this work, a candidate material has been identified based on its mechanical and shape memory properties. It has been demonstrated that important properties of material like glass transition temperature, elastic modulus, and strength can be tailored according to the need by changing the ratio of constituents. A dedicated experimental setup consisting of Uniaxial Tensile Machine (UTM), temperature control chamber, and a camera for Digital Image Correlation (DIC) has been used to carryout thermomechanical cycles of SMP. The parameters that affect the performance of cold programming like stress-relaxation time, structural relaxation time, and operating temperature have been studied. The stress-strain response for a complete shape memory cycle has been measured. Parameters determining the shape memory capabilities like shape fixity, recovery ratio, recovery speed of the material were evaluated. The merits and demerits of cold programming over other programming methods have been discussed by carrying out required experiments. The differences in both the programming methods and the underlying mechanism of shape memory effect have been discussed briefly in this paper. Present work is limited to the study of SMP for uniaxial tensile cases undergoing large deformation with small strain-rate and low rate of heating and cooling.



中文翻译:

环氧基形状记忆聚合物的冷编程

形状记忆聚合物(SMP)是一类智能材料,具有记忆不同形状并恢复原始形状的能力。常规方法是将SMP加热到其玻璃化转变温度(T g)以上并使其变形以获得所需的形状。加热后恢复为原始形状。这就是所谓的热编程。SMP编程的最新进展显示了一种新的编程方法(也称为冷编程)的有希望的结果。SMP在低于T g的温度下发生塑性变形赋予所需的形状。本文旨在通过冷编程方法对基于环氧树脂的SMP的形状记忆特性进行实验研究。在这项工作中使用的环氧聚合物是双酚A的二缩水甘油醚(DGEBA)和新戊二醇二缩水甘油醚(NGDE)。已经发现在各种温度下,不同比例的DGEBA和NGDE的机械性能,如弹性模量,拉伸强度和破坏应变。第t已经使用差示扫描量热法(DSC)测量了不同成分的组成。在这项工作中,已根据其机械和形状记忆特性确定了候选材料。已经证明,可以通过改变成分的比例来根据需要调整材料的重要性能,例如玻璃化转变温度,弹性模量和强度。由单轴拉伸机(UTM),温度控制室和用于数字图像关联(DIC)的相机组成的专用实验装置已用于执行SMP的热机械循环。研究了影响冷编程性能的参数,如应力松弛时间,结构松弛时间和工作温度。已经测量了完整形状记忆周期的应力应变响应。评估确定形状记忆能力的参数,例如形状固定性,恢复率,材料的恢复速度。通过进行所需的实验,已经讨论了冷编程优于其他编程方法的优缺点。本文简要讨论了编程方法的差异以及形状记忆效应的潜在机制。目前的工作仅限于单轴拉伸情况下的SMP的研究,这些情况发生大变形,应变率小,加热和冷却速率低。通过进行所需的实验,已经讨论了冷编程优于其他编程方法的优缺点。本文简要讨论了编程方法的差异以及形状记忆效应的潜在机制。目前的工作仅限于单轴拉伸情况下的SMP的研究,这些情况发生大变形,应变率小,加热和冷却速率低。通过进行所需的实验,已经讨论了冷编程优于其他编程方法的优缺点。本文简要讨论了编程方法的差异以及形状记忆效应的潜在机制。目前的工作仅限于单轴拉伸情况下SMP的研究,这种情况发生大变形,应变率小,加热和冷却速率低。

更新日期:2020-07-06
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