Randy Hay is a Senior Materials Research Engineer at the Air Force Research Laboratory. His research concerns processing – microstructure – properties relationships of high temperature structural ceramics, with emphasis on oxide-oxide and SiC-SiC ceramic matrix composites (CMCs). He has developed rare-earth orthophosphate and rare earth disilicate fiber coatings for oxidation-resistant CMC fiber-matrix interfaces, and developed fiber coating methods for these complex oxides. Methods to predict deformation twinning, diffusionless phase transformations, and transformation plasticity in rare earth orthophosphates, rare earth disilicates, and other complex materials with low symmetry were developed to understand and predict their mechanical properties. He has characterized and identified mechanisms affecting fiber strength during SiC fiber oxidation in air and steam, and developed predictive fracture mechanics models based on glass and/or crystalline SiO2 scale residual stress, including growth stress from oxidation volume expansion. Strength degradation at intermediate temperatures by environmentally assisted subcritical crack growth in oxide and SiC fibers is also a major research interest. He has also developed computational methods for 3-D microstructure quantification from 2-D section data and for statistical description of fiber coating thickness and grain size distributions and orientations, and is involved with development of polycrystalline yttrium aluminum garnet fibers for high energy optical applications.
Randall Hay
 Air Force Research Laboratory