Experiments on High Temperature Mechanical Properties and Stress Distribution Laws on Strain Isolation Pad

应变隔离垫高温力学性能试验及应力分布规律

¹ Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
² AVIC Chengdu Aircraft Design and Research Institute, Chengdu 610091, China
³ State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Received: 2 March 2018

Abstract

The tile is the main heat insulation part of a thermal protection system, and is attached to the outer surface of an orbiter through a strain isolation pad (SIP). In order to study its high temperature mechanical properties and stress distribution, experiments on flatwise tension, flatwise compression and flatwise shear are conducted in the environments of the room temperature of 23±2℃ and the 300℃ high temperature. The load-displacement curve, elasticity modulus and failure strain of the SIP are measured and calculated. Compared with the experimental results under the room temperature, the tension, compression and shear elasticity modulus of the SIP in the 300℃ high temperature environment fall by 9.68%, 9.24% and 8.73% respectively, and the tension and shear failure strain of the SIP in the 300℃ high temperature environment fall by 11.59% and 12.81% respectively. So, the high temperature causes the decrease of the stiffness and strength of the SIP. Its stress distribution is studied with the experimental results. Under the influence of tension, compression and shear force, the stress distribution of the SIP shows trends of low middle and high edge. Besides, shear stress and normal stress are produced under shear force, and the normal stress is tensile at one side and compressed at the other side. The above analysis shows that the edge of the SIP is high in stress and easy to damage.

摘要

防热瓦作为热防护系统（TPS）的主要隔热部件，其通过应变隔离垫（SIP）粘接于机体表面。为了进行SIP的高温力学性能及应力分布规律研究，在常温（23±2℃）和300℃高温2种试验环境下进行了SIP的拉伸、压缩和剪切试验，获得了试验件的载荷-位移曲线、弹性模量及破坏应变。相比常温下，在300℃高温下SIP的拉伸、压缩和剪切弹性模量分别下降了9.68%，9.24%和8.73%，此外在300℃高温下SIP的拉伸和剪切破坏应变分别下降了11.59%和12.81%，即高温引起了SIP刚度和强度的下降。利用试验数据进行了SIP的应力分布规律研究，结果表明在拉、压及剪切力作用下，SIP应力呈中间低边缘高的趋势。此外在剪切力作用下，SIP同时产生剪切应力和正应力，并且正应力一端受拉，另一端受压。由以上分析可知SIP的边缘处是高应力区域，易发生破坏，应给予足够的重视。