In this work the definition, classification and basic properties of meshfree methods have been reviewed first, followed by a summary of the mathematical and physical backgrounds of composite structures and low-velocity impact analyses. The properties and the applications of composite structures have been presented with a main focus on the application in the aeronautical industry. The polynomial point interpolation method (PPIM) and the radial point interpolation method (RPIM) are discussed in detail, since the developed approach in this study is based on these methods. The RPIM has been extended in order to model composite structures using the third order shell deformation theory (TSDT) which is more accurate than the classical laminate theory (CLT) particularly in the case ol' thick laminates. The developed new approach has been applied to study low-velocity impact of composites covering diversified geometric, material and loading situations. A spring mass model has been used to determine the contact force history using the Newmark integration method. The determined maximum contact force lias then been used as input load in a static analysis of the composite structure. To assess the impact induced damage consisting of fibre, matrix failure and delamiuation between layers, a Tsai-Wu based failure criterion has been applied. An extensive study of the radial basis function and RPIM parameters has been conducted to determine the optimum values applicable in the case of the analysis of composite structures. In order to examine the applicability of the present approach, the obtained results have been compared to computed and test results found in the literature. So far, most research activities in the field of meshfree methods are concentrating on the solution of problems of homogeonous and isotropic structures. It was the objective of this work to extend their scope for the analysis of problems of composite structures, consisting of many orthotropic layers with different material properties, with main focus on their behavior in the case of low-velocity impact. It has been found that meshfree approaches perform very well in solving these kinds of problems. The general solution procedure is rather similar to that of the mesh-based methods. Implicit time schemes, such as the Newmark method can he used to perform the time integration for the complete impact duration. The Tsai-Wu based method, which is also used in the finite element method, was incorporated in the meshfree formulation for damage assessment.
Meshfree methods for low-velocity impact analysis of composites
Maschenfreie Methoden zur Aufprallanalyse von Verbundwerkstoffen mit niedriger Geschwindigkeit
2009
109 Seiten, Bilder, Tabellen, 83 Quellen
Theses
English
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