Determining Residual Stresses in Thin-Walled Ceramic/Ceramic Composite Pipes

Fiber-reinforced ceramic materials exhibit excellent strength, toughness, and resistance to high temperatures and thermal shocks. To determine the service stress limit of a material, it is very important to determine residual stresses that are developed during the manufacturing processes. This work uses the laser speckle technique as a sensitive, noncontact, quantitative tool to determine residual stresses in thin-walled pipes made of ceramic/ceramic composite. The laser measurement is combined with an elastic solution to obtain both the radial and the tangential stress distributions along the thickness of the pipe. The proposed approach, suitable only for thin-walled cylinders, possesses different advantages with respect to simplicity and sensitivity. The results obtained show that this approach is more reliable and accurate than the strain gauge method.