Paper number 1363

MODE II AND MIXED MODE I/II DELAMINATION OF GRAPHITE/EPOXY COMPOSITE UNDER DYNAMIC LOADING CONDITIONS

Sylvanus N. Nwosu¹, David Hui², and Gregory Czarnecki³

1Department of Physics/Engineering, Dillard University, New Orleans LA 70122
2Department of Mechanical Engineering, University of New Orleans, LA 70122
3Wright Laboratory, Wright Patterson AF, Ohio 45433

Summary

This paper examines the split Hopkinson pressure application to mode II and mixed mode I/II delamination of unidirectional graphite/epoxy composites and the effects of dynamic loading on the energy release rate and absorption mechanism. The relationship between energy absorption and delamination follows a mode dependent power law behavior. Delamination increases linearly with mode ratio and impact energy up to a certain maximum that depends on the mode of fracture. Maximum delamination is reached when the reflected wave is more than 15% higher than the incident wave. The results show regions of damage mechanisms. The dynamic energy released rate in the present model differs slightly from quasi-static model. The differences are attributed to scaling effect or strain rate sensitivity in dynamic mode fracture failure. However, the characteristics of modes I and II contributions to the fracture toughness are the same as those observed in quasi-static test reported in the literature.

Keywords

delamination, dynamic interlaminar fracture, pure mode, mixed mode, energy absorbed, split Hopkinson pressure bar.