Experimental results are presented for elevated temperature (177°C), tension-compression fatigue tests performed on titanium-graphite (TiGr) hybrid laminates containing open holes. The key damage modes were identified as 0° ply splitting, facesheet cracking, and facesheet delamination. The growth of damage during fatigue resulted in large reductions of the local stiffness adjacent to the hole. This stiffness reduction was predominantly due to delamination of the facesheet from the polymer matrix composite core and showed a significant temperature dependence. Using a simple one-dimensional model it was shown that the delamination growth rates depend on the applied loading according to a "Paris" law, with an exponent of 1.9 on the cyclic strain energy release rate. This observation was substantiated by observations of delaminations growing in isolation in specimens containing facesheet seams.
展开▼
