The aim is to make in-situ measurements of the strains in both the tungsten matrix and the copper infiltrate in the mechanical testing machine on ENGIN-X. Mechanical tests will be held constant at a series of progressively higher loads and the diffraction data collected. Strains will be determined in both the tungsten and copper phases from the measured lattice spacings relative to those observed at zero load (zero reference). Mechanical tests will be repeated at specific temperatures up to a temperature at which significant extrusion and/or debonding of the copper phase becomes apparent. In addition, a preliminary measurement of powder samples of tungsten and copper at room temperature will enable a direct determination of the thermal stress in the composite under ambient conditions.