A STUDY OF MODE-I DELAMINATION CRACKS BY HIGH-MAGNIFICATION MOIRE INTERFEROMETRY

Delamination cracks in carbon-fibre/epoxy composites loaded in Mode-I have been studied by high-magnification moire interferometry. The moir e interferometer has the capability of switching between laser illumin ation for acquiring the displacement field and white-light illuminatio n for visualisation of the underlying microstructure. Four specimens w ith different stacking geometries have been investigated. The delamina tion cracks have been simulated by using Teflon films. The resulting d isplacement fields have been compared to numerical solutions calculate d by the finite-element method. The comparisons indicate that the Tefl on films for some of the specimens did not delaminate fully. Otherwise the agreement is good, confirming that the displacement field around such cracks is satisfactorily described by linear-elastic fracture mec hanics. The agreement was improved when a matrix-rich region in front of the crack tip was included in the finite-element model. (C) 1998 El sevier Science Ltd. All rights reserved.