Finite element modeling and non-destructive inspection of composite-honeycomb sandwich panels

Abstract

Composite-Honeycomb sandwich panels are structures designed for specific applications. These are extremely efficient in stiffness-to-weight and strength-to-weight situations. These qualities make the sandwich panels the most suitable structures for use in aircraft and space vehicles. A Finite Element model is developed on ANSYS for static and dynamic structural analysis of these panels. This model provides a very accurate assessment of sandwich panel's stiffness in static as well as transient modes. Non-destructive Inspection of these panels is, however, a problem and search to develop an efficient test method has been going on for a long time. Center for Non-Destructive Evaluations (CNDE) is currently developing an Instrumented Tap Tester with virtues of accuracy, speed, economy, simplicity, and portability. The test method provides quantitative measure of local stiffness values based on impact duration of a tap by investigating the force-time history response of a structure. The Finite Element model can be used to determine a correction factor for the new tap tester that can be applied to obtain more accurate measurements for stiffness values. The percentage loss of stiffness can then be used as a pass/fail criterion. A new technique is developed to introduce minute engineered flaws in sandwich panels during their fabrication. These samples and samples from actual aircraft surfaces are tap tested to evaluate tester's flaw detection capabilities.