Residual stresses in continuous-tungsten-fibre-reinforced Kanthal-matrix composites

Residual stresses were measured in four Kanthal matrix-continuous-tunsgten-fibre composites (with different tungsten fibre volume fractions V-f = 10, 20, 30 and 70vol.%) using neutron diffraction. Parallel to the fibres the stress in the Kanthal ranged from 40 MPa (V-f = 10vol.%) to 1100MPa (V-f = 70vol.%) compared with -1877MPa (V-f = 10vol.%) to -400 MPa (V-f = 70vol.%) for the tungsten. Perpendicular to the fibres the stress ranged from -52MPa (V-f = 10vol.%) to 620 MPa (V-f = 70vol.%) in the Kanthal compared with -778 MPa (V-f = 10vol.%) to -195 MPa (V-f = 70vol.%) in the tungsten. Assuming that the measured residual stresses were solely thermal in origin, predictions were made using concentric cylinder and finite-element models. In the absence of hardening data the assumed material behaviour was elastic-perfectly plastic and the predictions underestimated the measured stresses for all volume fractions. Nevertheless the model results were consistent with the experimental measurements. The transverse stress in the fibres is discussed in the context of the interface normal stress, which is significant to the global mechanical response.