Experimental investigation of the effect of temperature on the strength of polyimide contact structures.pdfVIP

Polymer Testing 54 (2016) 139e144 Contents lists available at ScienceDirect Polymer Testing journal homepage: /locate/polytest Test method Experimental investigation of the effect of temperature on the strength of polyimide contact structures Qinwei Ma a, Hetong Liu b, Hongtao Wang c, Libin Sun c, Shaopeng Ma a, * a School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, China b China Nuclear Power Engineering Company Ltd., Beijing 100840, China c Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China article info Article history: Received 31 May 2016 Accepted 14 July 2016 Available online 16 July 2016 Keywords: Polyimide Contact strength Temperature effect Yielding core Digital image correlation abstract A new photogrammetry based measurement technique for contact areas in line contact structures is developed. From the data collected by this technique, a method for measuring the contact strength of contact structures in high temperature applications is proposed. The contact strength of a line contact structure of polyimide at different temperatures is measured; the results show that the increase in temperature decreases the contact strength of the structure. The effect of temperature on the contact strength is studied by investigating the occurrence and evolution of yielding core within the structure at different temperatures. The decrease in the yield strength and elastic modulus of the polyimide material at high temperature induces core yielding at lower loads and eases the propagation of core yielding to the surface. ? 2016 Published by Elsevier Ltd. 1. Introduction Because polymers are used as both structural and functional materials in some contact structures [1,2], such as that of a cylinder or a sphere placed on a plate and subjected to a load [3], the load capacity of these structures (i.e., the contact strength) should be measured and analysed. Such polymer structures might be used in environmen