Remote optical detection of geometrical defects in aerogels and elastomers using phosphor thermometry

Abstract Detecting structural damage in the form of geometrical defects in materials that operate under extreme conditions or serve as critical structural components is essential. In this work, the feasibility of using thermographic phosphors as a non-destructive, remote, instantaneous, and customizable sensing mechanism for detection of structural damage was investigated. The two materials studied were (1) Sylgard 184 elastomer and (2) silica aerogels. Two different types of structural damage were investigated in samples of increasing thickness, up to a maximum of 18 mm. To accurately interpret the results, heat flux measurements were also collected from both material types. The changes in the thermal profile of the material as a result of material defects were used to infer information about the structural health of the material. La2O2S:Eu and Mg3F2GeO4:Mn were chosen for the study since their temperature sensitivity range complemented one another and allowed for measurements from cryogenic to 200 °C. It was determined that fracture and failure in both aerogels and Sylgard 184 could be detected by phosphor thermometry and the limit of its resolution was ultimately determined by the thermal properties of the material, the choice of phosphor, and ambient temperature.