Vol.10, No 2, 2012 pp. 91 - 104
UDC 669.1; 620.175
EQUIVALENT STIFFNESS AS MEASURE OF LOW VELOCITY IMPACT DAMAGE OF COMPLEX COMPOSITE STRUCTURES
Giangiacomo Minak1, Snežana Ćirić Kostić2, Zlatan Šoškić2, Nenad Radović1
1Alma Mater Studiorum University of Bologna, Department for Industrial Engineering, Italy
2University of Kragujevac, Faculty of Mechanical and Civil Engineering in Kraljevo
E-mail: soskic.z@mfkv.kg.ac.rs
This paper presents an analysis of the application potentials implied in the equivalent stiffness changes of complex mechanical structures as a measure of damage caused by low-velocity impacts. In a series of drop-weight tests of a commercial composite component, the impact force time variation is measured, and by calculating the respective displacement of the impacted structure, the stiffness of the structure in impacted points before and after the impacts is calculated. The determined stiffness change serves as the basis for defining a measure of damage extent that is compared to the damage extent measures based on characteristic values of the measured force. It is shown that the measure of damage based on change of stiffness has correlation with the measure of damage based on reduction of loading capacity of the structure, but it does not have correlation to the measure of damage based on ratio of maximal impact force and force needed for initial material failure.
Key words: Composite Structures, Low Velocity Impacts, Damage
EKVIVALENTNA KRUTOST KAO MERA OŠTEĆENJA SLOŽENIH KOMPOZITNIH STRUKTURA PRI UDARIMA MALIM BRZINAMA
Rad predstavlja analizu mogućnosti primene ekvivalentne krutosti složenih mehaničkih struktura kao mere oštećenja prouzrokovanih udarima malih brzina. U serijama testova kontrolisanih udara u komercijalnu komponentu načinjenu od kompozitnog materijala merena je promena udarne sile tokom udara, a daljim proračunom deformacije udarane komponente je izračunata njena ekvivalentna krutost u udaranim tačkama pre i posle udara. Na osnovu utvrđene promene krutosti definisana je mera oštećenja koja je upoređena sa merama oštećenja zasnovanim na karakterističnim vrednostima izmerene udarne sile. Pokazano je da mera oštećenja zasnovana na promeni krutosti ima korelaciju sa merom oštećenja zasnovanoj na smanjenju nosivosti strukture, ali da nema korelaciju sa merom oštećenja zasnovanoj na odnosu maksimalne udarne sile i sile pri kojoj nastaje početno oštećenje komponente.
Ključne reči: kompozitni materijali, mašinske konstrukcije, udari malim brzinama, oštećenja