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THIS WORK AIMS TO CONTRIBUTE FOR THE DEVELOPMENT OF SHM SYS-TEMS BASED ON VIBRATION METHODS TO BE APPLIED ON SANDWICH STRUCTURES. THE MAIN OBJECTIVE IS FOCUSED ON EXPERIMENTAL DAM-AGE IDENTIFICATION VIA CHANGES IN THE FREQUENCY RESPONSE FUNC-TION (FRF) WITH THE USAGE OF DAMAGE METRICS. SPECIMENS OF SANDWICH STRUCTURES MADE FROM SKINS IN EPOXY RESIN REINFORCED BY GLASS FIBER AND A CORE OF PVC FOAM ARE MANUFACTURED. FIRST, PRELIMINARY NON-DAMPED FINITE ELEMENT (FE) MODELS ARE PER-FORMED, AND RESULTS OBTAINED ARE USED TO DEFINE THE FREQUENCY RANGE OF INTEREST FOR THE EXPERIMENTAL PROCEDURE. AFTER THAT, VI-BRATION EXPERIMENTAL ANALYSES ARE CARRIED OUT ON UNDAMAGED SPECIMENS. THE NATURAL FREQUENCIES ARE COMPARED TO THE PRELIMI-NARY FE RESULTS. SECOND, EXPERIMENTAL ANALYSES ARE PERFORMED ON DAMAGED SPECIMENS WITH PIEZOELECTRIC SENSORS OR NOT. THEN, DAMAGE METRIC VALUES ARE CALCULATED BASED ON FRFS FOR DAM-AGED AND UNDAMAGED STRUCTURES, WHICH WERE OBTAINED FROM EX-PERIMENTAL AND FE ANALYSES (WITH DAMPING EFFECTS). IN ADDITION, A NEW PROCEDURE IS PROPOSED TO IMPROVE THE QUALITY OF RESULTS PROVIDED BY THE DAMAGE METRIC. IT IS SHOWN THAT THE NEW PROCE-DURE IS VERY EFFECTIVE TO IDENTIFY THE DAMAGE USING BOTH AMPLI-TUDE AND PHASE FROM FRFS. LASTLY, IT IS DISCUSSED THE POTENTIALI-TIES AND LIMITATIONS OF THE FE MODEL TO PREDICT DAMAGE METRIC VALUES, COMPARING TO EXPERIMENTAL DATA.
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