Harea E, Datta S, Stěnička M, Maloch J, Stoček R
Centre of Polymer Systems, Tomas Bata University in Zlín, Tř. Tomáše Bati 5678, 76001 Zlín, Czech Republic.
Polymers (Basel). 2021 Jul 22;13(15):2411. doi: 10.3390/polym13152411.
A monotonous relation between strain and measured electric resistance is highly appreciated in stretchable elastomer sensors. In real-life application the voids or technological holes of strained samples often induce non-homogeneous local strain. The present article focused on studying the effect of non-homogeneous local strain on measured direct current (DC) effective electric resistance (EER) on samples of natural rubber (NR), reinforced with 50, 60 and 70 phr of carbon black (CB). Samples were imparted geometrical inhomogeneities to obtain varied local strains. The resulting strain distribution was analyzed using Digital Image Correlation (DIC). EER exhibited a well-detectable influence of locations of inhomogeneities. Expectedly, the EER globally decreased with an increase in CB loading, but showed a steady increase as a function of strain for 50 and 60 phr over the complete testing protocol. Interestingly, for 70 phr of CB, under the same testing conditions, an alternating trend in EER was encountered. This newly observed behavior was explained through a novel hypothesis-"current propagation mode switching phenomenon". Finally, experimentally measured EERs were compared with the calculated ones, obtained by summing the global current flow through a diversity of strain dependent resistive domains.
在可拉伸弹性体传感器中，应变与测量电阻之间的单调关系备受青睐。在实际应用中，应变样品的空隙或工艺孔洞常常会引起局部应变不均匀。本文重点研究了局部应变不均匀对天然橡胶（NR）样品测量直流（DC）有效电阻（EER）的影响，该天然橡胶用50、60和70份每百份橡胶（phr）的炭黑（CB）进行增强。对样品施加几何不均匀性以获得不同的局部应变。使用数字图像相关（DIC）分析所得的应变分布。EER表现出不均匀性位置的可明显检测到的影响。不出所料，EER总体上随着炭黑含量的增加而降低，但在整个测试过程中，对于50和60 phr的情况，EER随应变呈稳定增加。有趣的是，对于70 phr的炭黑，在相同测试条件下，EER出现了交替趋势。这种新观察到的行为通过一个新的假设——“电流传播模式切换现象”来解释。最后，将实验测量的EER与通过对通过各种应变相关电阻域的全局电流求和得到的计算值进行了比较。
