Paper number 563


Joakim Schön1 and Anders F. Blom1,2

1Structures Department, The Aeronautical Research Institute of Sweden
Box 11021, SE-161 11 Bromma, Sweden
2Department of Aeronautics, Royal Institute of Technology
SE-100 44 Stockholm, Sweden

Summary A model for predicting the fatigue life of composites at different load ratios have been developed. The basic assumption of the model is that the fatigue life of a specimen is governed by delamination growth. The model is based on calculation of delamination growth by integration of Pari's law. It is assumed that fracture for different load ratios, but with the same peak-load magnitude, will occur at the same delamination length. In addition, it is assumed that the energy release rate does not vary with delamination length. The model is able to predict the fatigue life for tension-tension, compression-compression, and tension-compression fatigue. In comparison with experimental results for unnotched specimens the model shows good agreement. Due to the large exponent in Pari's law for composites the model is sensitive to errors in the parameters used.
Keywords fatigue life, load ratio, delamination growth, notch, life-prediction model.

Theme : Mechanical and Physical Properties ; Fatigue

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