Residual-stress-induced crack formation in robocasted multi-material ceramics: Stress considerations and crack prevention

Layered multi-material ceramics are natural candidates for modern engineering applications due to their attractive mechanical properties. Residual stresses caused, for example, by a thermal mismatch during the processing of these materials can significantly affect their mechanical properties. In this work, Raman in-vestigations were performed to estimate these residual stresses in layered reaction-bonded silicon carbide (RBSC) and reaction-bonded boron carbide (RBBC) composites fabricated by robocasting. The Raman measurements show that the residual stress in the silicon phase of RBSC and RBBC composites has a different sign, which can explain the crack formation that occurred after Si infiltration. To adjust the stresses and prevent this cracking, a new paste composition was investigated. SEM micrographs and Raman measurements showed that almost crack -free layered composites with similar stresses in the different layers could be realized. In addition, well-known analytical approaches were used to calculate these residual stresses.

Automated summary

Raman investigations were performed to estimate the residual stresses in layered composites, and it was found that there were differences in stresses among different layers. By adjusting the paste composition, crack-free layered composites were successfully obtained.