pluginActive Sensing of Impact Damage in Composite Sandwich Panels by Low Frequency Lamb Waves.pdf

THE AERONAUTICAL JOURNAL MAY 2008 279 Technical Note Active sensing of impact damage in composite sandwich panels by low frequency Lamb waves C. Soutis and K. Diamanti Aerospace Engineering The University of Sheffield Sheffield, UK ABSTRACT ABBREVIATIONS The development of a robust non-destructive system to detect and CFRP carbon fibre reinforced plastics monitor the extent of damage in carbon fibre reinforced plastics IDTs interdigital transducers (CFRP) during service life is a key problem in many practical appli- NDE nondestructive evaluation cations, especially in the aircraft industry. The lack of such PZT piezoceramic transducer technique has severely limited the potentially extensive use of SIMS structural integrity monitoring system composite materials. In this study a cost and time effective TOF time of flight inspection strategy for in-service health monitoring of composites is ∆TOF difference of time of flight demonstrated using the fundamental anti-symmetric A0 Lamb mode at frequencies of 15-20kHz. In principle, this method involves analysis of the transmitted and/or reflected wave after interacting 1.0 INTRODUCTION with the test-piece boundaries or discontinuities (defects). In the The evaluation of structural integrity using Lamb waves has long been present work, the applicability of the technique to composite acknowledged as a very promisi