Comparison of residual strains measured by X-ray and neutron diffraction in a titanium (Ti-6Al-4V) matrix composite

This research compares matrix thermal residual strains measured in a contin uous fiber reinforced SiC/Ti-6Al-4V titanium matrix composite (TMC) using X -ray and neutron diffraction with finite element predictions. The strain de pendence on the strains for several reflections (105, 204, 300, 213 and 312 ) of the matrix were explored at the surface (X-ray) and in the bulk (neutr on). To determine the longitudinal surface strains from the X-ray measureme nts for comparison with the neutron values, the E-phi psi versus sin(2)psi plots were extrapolated to psi = 90 degrees. Continuum micro-mechanics base d multi-ply finite element models (FEM) simulating rectangular and hexagona l fiber distributions were explored for calculating average surface and bul k strains. For different reflections, the experimentally determined surface measured strains ranged from + 1904 + 424 to + 2974 +/- 321 mu epsilon and the bulk measurements ranged from + 2269 +/- 421 to +/- 3022 +/- 1134 mu e psilon. These values contrast with the single valued FEM prediction of + 32 00 mu epsilon which was the same for both the surface and the bulk. (C) 199 9 Elsevier Science S.A. All rights reserved.