High spatial resoln. synchrotron X-ray strain mapping has been used to map the elastic matrix and fiber strains in the vicinity of a fatigue crack in a Ti-6Al-4V/SCS6 SiC fiber composite. A 0.61 mm fatigue crack was initiated and grown in three-point-bending. By using an in-situ loading stage it was possible to map the crack opening (longitudinal) strain distribution at Kappl=Kmax and Kappl=0. In the far field region, significant thermally induced stresses were evident, being compressive in the fibers and tensile in the matrix. Around the notch and in the wake of the crack tip essentially no residual strain and only small interfacial shear stresses were found in the unloaded case, indicative of a debonded/damaged interface. At Kmax the max. tensile stress in the matrix is in the vicinity of the crack tip, whereas for the SiC fibers the max. stress is in the bridging zone in the wake of the crack. The perturbed zone extends about +-1.5 mm either side of the crack. It was at the boundary of this zone that the max. interfacial shear stresses (.apprx.80 MPa) were measured in the loaded stage. A small area of tensile strain in front of the crack tip in the unloaded condition suggests frictional resistance from the bridging fibers acts to keep the crack slightly open. A simple 3-dimensional finite-element model has been developed to help interpret the results. The crack is introduced statically by node release and the Coulomb friction law governs the interface strength. The results of the model are compared to the synchrotron strain measurements. This comparison confirms the degrdn. of the interface strength in the wake of the crack. [on SciFinder (R)]