Aircraft Technologies Damage Assessment in Smart Composite Structures: the DAMASCOS Programme S.G. PIERCE, F. DONG, K. ATHERTON, B. CULSHAW, K. WORDEN, G. MANSON, T. MONNIER, P. GUY, J-C. BABOUX, J. ASSAD, E. MOULIN, S. GRONDEL, C. DELEBARRE, V. AGOSTINI, P-P. DELSANTO, I. GENESIO, E. MINO, C. BOLLER The DAMASCOS (Damage Assessment in Smart Composite Structures) project is a European Union funded programme of work bringing together a number of academic and industrial partners throughout Europe. The aim of DAMASCOS is to apply new ultrasonic detection and generation techniques integrated within the structure, together with advanced signal processing to realise damage assessment and ageing characterisation in composite structures. Thispaper describes the background, experimental findings and future applications of the technology as the project moves into its final phase. he fundamentals behind the DAMASCOS project are best illustrated in fi,k~un ' 1. The sys- tem formed an ultrasound based interrogation system for dam- age assessment in advanced glass and carbon reinforced plastic materials (GRP and CFRP). Acoustic Lamb waxes could be launched into the sample from piezoelectric sources (PZT), and detect- ed using either similar PZT transducers or optical fibre receivers. Since the sam- pie materials were typically of thin plate construction, we have concentrated exclusi\'ely on the propagation of ultra- sonic Lamb waves [1] within the sam- pies. Changes in the condition of the sample under test, affected parameters of the l~amb wave propagation charac- teristics, and in this faslnion, by the application of suitable signal processing procedures, it was possible to infer the presence and position of structural damage within the sample plates. The experimental programme was compli- mented by modelling of Lamb wave propagation within the samples, and the interaction with defects. Typical acoustic sources and detectors used in DAMASCOS are shown in fi- ,k'tm' 2 together with some of the final target inspection structures in ti<un' 3. The DAMASCOS approach to signal processing and data interpretation rep- resented perhaps the most radical departure fronl clas- sical techniques. A~n'~z~r'"] Previous work [2, 31 has tended to focus on the echo dis- crimination of sig- ~ nals in a pitch- catch arrangement. This approach can be frustrated by the complexity of Lamb wa\'e propa- gation; for in addi- tion to problems of low signal ampli- tude and edge re- flection effects, the propagation characteristics of ultrasonic Lamb wa\es can exhibit considerable pulse velocity dispersion and complica- tions due to multiple mode propagation I4, 51. Some noxel approaches to ad- dressing some of these problems have included wavelet processing to enhance Acousflcdetecton [ PZT/Op~cal fibres Slgnal processing INTERPRIETATION OF DAMAGE Modelling of ~l propagation insamplel Figure i. Illustration of the basic DAMASCOS system concepts. defect visibilih [t~], system identifica- tion [7] and signal regeneration 1~ 9, 10]. Our approach in DAMASCOb has been to adopt a statistical method to look for small changes in the re- ceived signal to indicate a change in fix' system, which may be due to damage Figure 2. DAMASCOS acoustic sources, (a) INSA mono-element, (t9) UV multi-element, (c) EADS dual~single element, D