Stress Relaxation of Cellular Silicone Material: 1980.
ALLIED BENDIX AEROSPACE KANSAS CITY MO
Pagination or Media Count:
Bendix Kansas City currently is involved in generating stress relaxation information for cellular silicone materials that are formed with urea leachable filler. There are two types of base polymers used in the test equilibrium type random copolymer and condensation type block copolymer. Each of these was compounded to provide finished materials with nominal apparent densities of 0.34 and 0.52 gcm3. Three sample variations of 1.17, 1.52, and 2.54 mm nominal thickness were prepared from the lower density product, and two sample variations of 1.52 and 2.54 mm nominal thickness were prepared from the higher density product. Each of the materialthickness combinations was compressed to nominal compressions of 20 and 40 percent, with nine replicates at each condition. A specially designed compression fixture for aging is used to maintain a specific compression on the cellular sample at room temperature, and a universal test machine is used to acquire the load data. The load was recorded at initial assembly and at selected times thereafter. In all, a total of 180 specimens are in test, 90 equilibrium type material samples that have been stored 5 years and 90 condensation type material samples that have been stored for 4 years. Each condition for each material type has nine replicates. Of these nine samples, two are 3 year controls, two more are 10 year controls, and five are tested regularly. The current data still support the statement that the time dependent loss of load bearing properties is approximately log-linear, with the major differences found to be between the material types and between the two densities of each material type. MM