Publication Date


Document Type


Committee Members

Jeremy Daily (Committee Member), George P. G. Huang (Other), Nathan Klingbeil (Advisor), Nathan Klingbeil (Committee Chair), Ravi Penmetsa (Committee Member), Joseph F. Thomas, Jr. (Other)

Degree Name

Master of Science in Engineering (MSEgr)


Recent work has proposed a dissipated energy theory of fatigue crack growth in layered materials under mixed-mode loading. An inherent assumption of this prior work is that a perfect crack exists along the interface joining the top and bottom layers. The current work extends the approach of previous studies to incorporate a grading of plastic properties between the two layers through parametric finite element modeling with ABAQUS. An elastic-plastic 2D model using 8-node biquadratic elements was used to map the plastic dissipation of a two layer specimen with a grading of plastic properties parallel to the crack face. This property gradient allows for a more realistic representation of the plastic dissipation accumulated during a steady state cracking configuration. As a result, more accurate fatigue crack growth rates in layered material systems can be predicted. It was found that incorporation of a graded layer increased the amount of plastic dissipation. While this graded layer effect cannot be ignored, plastic dissipation is still dominated by the mode of loading.

Page Count


Department or Program

Department of Mechanical and Materials Engineering

Year Degree Awarded