Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Weight functions for composite repairs to stiffened panels
This paper presents a weight function technique for calculating the stress intensity factors for composite repairs to cracks emanating from an internal notch, corrosion blend out, or a free edge under arbitrary loading in rib stiffened panels. The predictions are compared with both finite element and experimental values. Existing design formulae for the composite repair of cracked structures are limited to simple geometries and loads. However, it is well know that load bi-axiality can have a significant effect on the stress intensity factors associated with cracks at stress concentrators. To this end the present paper has presented a weight function based approach that extends existing 2D design formulae for composite repairs to allow for repairs to cracked holes, edge cracks, and stiffened structures under arbitrary multi-axial loading. The weight functions developed in this paper have been linked to NE-NASTRAN and to NASA crack growth codes thereby enabling the methodology to be used in conjunction with the standard finite element analysis models of the uncracked aircraft. As such they represent a significant extension to existing design formulae which are limited to the case of uniform loading and simple geometries. For composite repairs to cracked holes this paper supports the finding first presented in that the solution for a crack at a notch repaired with a composite patch differs from that obtained for repairs to centre cracks in that the maximum K does not correspond to the asymptotic limit. Since K reduces from a peak value to its asymptotic value crack growth will be retarded in this regime. As such to accurately determine the effect of a composite patch on the fatigue life it is necessary that this feature be included. As such using existing methods for analysing crack growth at a weephole or a corrosion blend out under a composite patch is inappropriate.
Weight functions for composite repairs to stiffened panels
This paper presents a weight function technique for calculating the stress intensity factors for composite repairs to cracks emanating from an internal notch, corrosion blend out, or a free edge under arbitrary loading in rib stiffened panels. The predictions are compared with both finite element and experimental values. Existing design formulae for the composite repair of cracked structures are limited to simple geometries and loads. However, it is well know that load bi-axiality can have a significant effect on the stress intensity factors associated with cracks at stress concentrators. To this end the present paper has presented a weight function based approach that extends existing 2D design formulae for composite repairs to allow for repairs to cracked holes, edge cracks, and stiffened structures under arbitrary multi-axial loading. The weight functions developed in this paper have been linked to NE-NASTRAN and to NASA crack growth codes thereby enabling the methodology to be used in conjunction with the standard finite element analysis models of the uncracked aircraft. As such they represent a significant extension to existing design formulae which are limited to the case of uniform loading and simple geometries. For composite repairs to cracked holes this paper supports the finding first presented in that the solution for a crack at a notch repaired with a composite patch differs from that obtained for repairs to centre cracks in that the maximum K does not correspond to the asymptotic limit. Since K reduces from a peak value to its asymptotic value crack growth will be retarded in this regime. As such to accurately determine the effect of a composite patch on the fatigue life it is necessary that this feature be included. As such using existing methods for analysing crack growth at a weephole or a corrosion blend out under a composite patch is inappropriate.
Weight functions for composite repairs to stiffened panels
Gewichtungsfunktionen bei der Reparatur von Verbunden in versteiften Panele
Jones, R. (Autor:in) / Chiu, W.K. (Autor:in) / Marshall, I.H. (Autor:in)
Engineering Failure Analysis ; 11 ; 49-78
2004
30 Seiten, 30 Bilder, 19 Tabellen, 31 Quellen
Aufsatz (Zeitschrift)
Englisch
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