Spectrum Slam Fatigue Loading of Sandwich Materials for Marine Structures
2010 (English)Conference paper (Other academic)
Sandwich materials are more frequently used in high speed craft and ferries. The motivation is reduced weight and associated operational cost. The hull structure in these vessels is subjected to repeated (fatigue) slamming loads (high strain rate loading). Scantling societies treat sandwich materials differently in their design rules. In common reduction or safety factors on the static strength of sandwich materials are used calculating the design stress. In most rules there is no explicit consideration of fatigue performance nor of the altered material properties related to high strain rate loading. In this work actual response measurements on a high speed vessel are used to formulate a tentative slam fatigue loading spectrum for sandwich core materials. This spectrum is then used in the testing of one type of core material common in hulls panels, Divinycell H200. The slam spectrum fatigue results are then compared to fatigue test results based on constant amplitude loading based on a method of equivalent stress. Earlier studies indicate that slamming fatigue do not affect the life compared to constant amplitude loading. However there are also studies that indicate that both a static overload (post the yield point) prior to fatigue loading, and block sequence fatigue loadings with initial high amplitudes followed by low amplitude have a detrimental effect of the fatigue life. In the current study both various amplitudes and high strain rates are included in the fatigue loading sequence. The spectrum fatigue results match the fatigue life from the constant amplitude loading. However, the number of samples is limited and the different effects of fatigue at high strain rates and fatigue block sequence are not fully clarified. It is possible that those effects may counteract each other in the current work. Further studies on sandwich foam core material properties and improvement of methods for material characterization is concluded to be of interest and will follow.
Place, publisher, year, edition, pages
IdentifiersURN: urn:nbn:se:kth:diva-57936OAI: oai:DiVA.org:kth-57936DiVA: diva2:472706
Ninth International Conference on Sandwich Structures (ICSS-9) in Pasadena, California, 14-16 June 2010
QC 201201272012-01-272012-01-042012-01-27Bibliographically approved