We attempted to characterize by neutron powder diffraction the monoclinic 0 phase that is known to form at low temperatures in dilute Pu-Ga alloys. This attempt was unsuccessful, as we did not detect any transformation to the 0 phase, but instead observed a line-broadening effect in the fcc phase. This effect is large enough to be visible in the raw diffraction data and is highly anisotropic in crystal space. The onset temperature of the line broadening (150 K) coincides with previous observations of the -0 transformation. Bulk 0 was not observed. We believe that the development of 0 nuclei creates a spatially inhomogeneous stress distribution in the matrix, which in turn exhibits an anisotropic response, governed by its elastic anisotropy. We have analysed this observation of anisotropic microstrains in terms of the fictive microstresses required to produce them by elastic deformation. During the course of this work, we found a pseudo-isotope effect in the room temperature lattice constants of Pu-Ga alloys. The alloys made from nominal 242 Pu isotope show systematically higher lattice constants than the corresponding 239 Pu alloys, and the size of the effect is proportional to the Ga concentration. We believe that this effect is associated with the higher levels of radiation damage from isotopic impurities in the 242 Pu alloys.

In this study, frequency response functions (FRF) measured by piezoelectric Macro-Fiber Composites (MFC) are used to detect subsurface delamination in a composite plate. The plate is impacted to seed damage in the form of ply delamination. Then, the MFC-based active-sensing system exerts an excitation into the plate, and measures the subsequent responses. Traditional piezoceramic materials are also mounted in comparable locations on the plate to compare their performances. FRF and damage indicator features are derived from the measured signals and used to assess the condition of the plate. Validation of the delamination is completed using an ultrasonic C-scan method. The effective area of observed damage is well correlated to the damage indicator feature.