Damage detection and localization in a composite cylinder using FRF curvature method

Application of composite materials has been widelyexpanded in recent years. Despite low weight and highstrength of these materials, early failure and theirweakness in vibrational environments are the mainobstacles in using these materials in dynamic loadingenvironments like impacts. Detection of inter-laminardelamination in preliminary stages as one of the mostcommon failures in laminated composites is veryimportant for the future life of structures. In this study,the effect of a small size delamination on the modalbehavior and frequency response functions (FRFs) isexperimentally investigated. Among usual damagemechanisms, the effect of impact which reveals itselfmostly as inter-laminar delamination is considered asdamage and the size of delamination, which is in directrelation with the energy of impact, is increased in fourstages. In each state, modal analysis is implemented andresults are compared with those of other states.Experimental modal analysis has shown that for theproposed damage, changes in natural frequencies andmode shapes are ignorable. However, raw data offrequency response functions may leads to damageidentification due to the variation of its features withrespect to damage size. To localize this kind of damage,the curvature of FRFs are calculated from experimentaldata in measurement points and is compared with thoseof the healthy cylinder where by choosing the optimumfrequency range, location of delamination isprognosticated correctly.

کلیدواژه ها:

Composite Cylinder ، Modal Analysis ، Delamination ، Damage Detection ، FRF Curvature method