Date of Award

2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Shivakumar, Kunigal

Abstract

Eco-Core is a fire resistant structural core material that was developed at North Carolina A&T State University in 2003. During the last 10 years, mechanical, fracture and fatigue properties as well as resistance to sea water were established for Eco-Core. A design methodology for Eco-Core in sandwich structures was provided. The objective of this research was to develop a dynamic constitutive equation for Eco-Core in a multi-axial stress state that is valid for both static and dynamic loadings, and then demonstrate the model to be used in a commercial code to solve real life problems. A special tri-axial loading and strain measurement test fixture was developed and used in static and dynamic tests. The material was tested at strain rates ranged from 3 10 /s to 3500/s. Analysis of the results showed that the net-deviatoric stress is independent of lateral stress. Based on the test results and a multi-variable regression analysis, a two part constitutive equation was developed. The first part was for the linear response and the second part was for the non-linear response that covers translation, crushing and densification of micro bubbles in the Eco-Core. The equation was validated by independent experiments and simulation by LS-DYNA. The dynamic energy absorption capability for Eco-Core was found to be superior compared to commercial materials such as PVC foam, Rohacell foam and Balsa wood.

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