Parametric Studies of Thermographic Detection of Disbonds in Laminated Structures Using Computational Simulations

Abstract

A quantitative assessment of a structure's material characteristics contributes to the safety, reliability, and useful lifetime of a structure. Thermographic nondestructive evaluation has advantages over other methods in that it is a noncontacting, quantitative measurement of the material integrity which can inspect large areas in a short period of time. A disbond between layers of a laminated structure will prevent heat from penetrating from the surface layer to the subsurface layers and will result in an increase in temperature over the disband. The limits of this technique for detection of disbands in solid rocket motors was investigated by computational simulation of the thermographic technique. This has an advantage over an experimental investigation, since many sample configurations and flaw sizes can be investigated at a fraction of the cost and time required for sample fabrication, data acquisition and analysis. This paper presents a series of simulations varying parameters that affect the thermal contrast such as heating time, disband size, and thickness of the surface layer. Experimental results are presented for comparison.