Polymer matrix composite (PMC) materials are ideal for aerospace structural applications, such as cryogenic fuel tanks of Reusable Launch Vehicles (RLVs) and Expendable Launch Vehicles (ELVs), due to their high strength-lo-weight and stiffness-to-weight ratio. For the confident application of these materials, it is necessary to evaluate the permeation of cryogenic fuel caused due to transverse matrix cracks in conjunction with inter-ply delaminations resulting in an intersecting network of passages. In this paper, an expression for predicting delaminated crack opening displacement (DCOD) is derived based on first-order shear laminate theory applied to a five-layer model. The DCOD obtained using the five-layer model is verified using a two-dimensional finite element analysis. A mathematical model to predict permeability in graphite-epoxy laminate system (IM7/5250-4) is developed using Darcy's law for isothermal, viscous flow of gases through porous media. The result obtained from the five-layer model is used as input to the permeability model. Using this model, the permeability is calculated for a quasi-isotropic laminate of lay-up (0/45/-45/90)s for a given delamination length, crack density and loading conditions. Also, a simple methodology to model stitch cracks has been proposed to address experimental observations. Model verifications are carried out by comparison with finite element analyses, and by comparison with permeability test data provided by the Air Force Research Laboratory.
Modeling of permeability in composite laminates with delaminations and stitch cracks
2006
17 Seiten, 15 Quellen
Conference paper
English
Anwendung in der Luft- und Raumfahrt , Delaminierung (Schichtablösung) , Faserbruch , Finite-Elemente-Methode , Flugkraftstoff , flüssiger Brennstoff , Isotropie , Kältetank , Kraftstoffbehälter , Leichtbauweise , Maschengeometrie , mathematisches Modell , mechanische Beanspruchung , mechanische Permeabilität , Polymermatrix-Verbundwerkstoff , Querriss , Raketenbau , Rissausbreitung , Rissdichte , Rissöffnung , Tankcontainer , Tieftemperaturtechnik , Weltraumrakete , Wiederverwendbarkeit
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