Rheological behaviour and thermal dilation effects of alumino-silicate adhesives intended for joining of high-temperature resistant sandwich structures

The study is concerned with inorganic adhesive layers located between the CMC composite skin and the Si-O-C ceramic foam core of sandwiches intended for high-temperature use. Two types of alumino-silicate adhesives (mastics) were tested for use as the bonding layer. The rheological properties of adhesive and its dimensional changes during high-temperature curing play a key role in terms of successful manufacture and subsequent use at high temperatures. In order to characterise these properties, specimens consisting only of the dried adhesive were subjected to compression tests conducted at increasing temperature from 300 to 1000 °C. These experiments were carried out via the application of two loading modes using both the static pre-load and cyclic loading methods. The above results were compared with thermal expansion records determined from fully-cured adhesives. In addition to the above investigation, the mechanical properties of the adhesive joint were measured employing both the DCB and shear tests.