The growing use of marine composite materials has led to many technical challenges and one is predicting Iifetime durability. This analysis step has a arge uncertainty due to the lack of data from in-service composite vessels. Analytical models based on classical lamination theory, finite-element analysis, ship motions, probability and wind and wave mechanics were used in this project to predict huIl Iaminate strains, and fatigue tests were used to determine S-N residual stiffness properties of coupons. These prectictions and test data were compared against two cored fibergtass sisterships having significantly different fatigue histories and undamaged laminates representing a new vessel. Strains were measured while underway and good correlation was achieved between predictions and measurements. Fatigue damage indicators were identified which could be used in vessel inspection procedures. Endurance limits were found to be near 25 % of static failure load, indicating that a fatigue design factor of four is required for infinite service with this material. Standard moisture experiments using boiling water were compared with long-term exposure. Results indicated the boiling water test yielded significantly conservative values and was not a reliable means of predicting Iong-term effects. Panel tests were compared with a combined coupon and finite-element procedure. Results indicated the proposed procedure was a viable substitute, at least for the materials studied. A rational explanation for using thicker outer skin laminates in marine composites was identitied through single-sided moisture flex tests. These showed that the reduced strength and stiffness due to moisture of the outer hull skin laminate could be compensated by increased thickness. Although the resulting unbalanced laminate is not ideal from a warping standpoint, the approach leads to consistent tensile failure of the inner skin when subjected to normal loads. Permeability considerations make this desirable for hull laminates.
Fatigue prediction verification of fiberglass hulls
Verifikation von Dauerfestigkeitsvorhersagemethoden zur Auslegung von Glasfaserschiffsrümpfen
Marine Technology and Sname News ; 38 , 4 ; 278-292
2001
15 Seiten, 14 Bilder, 8 Tabellen, 53 Quellen
Article (Journal)
English
Schiffbau , Dauerfestigkeit , Design (Entwurf) , Schiffsrumpf , Glasfaserverstärkung , Zuverlässigkeitsvoraussage , Verifikation , Verbundwerkstoff , Prüfverfahren , analytische Untersuchung , Methode der finiten Elemente , Theorie-Experiment-Vergleich , Wöhler-Versuch , Dehnungsmessung , Feuchtigkeitsgehaltprüfung , Steifigkeit