Verification of Fastener Modeling Techniques for Joining Composite and Metallic Assemblies

Structural analysis of aircraft components has involved the use of finite element method (FEM) analysis for many years. The transition from all metallic aircraft to hybrid constructions of composite and metallic materials has added complexity. Analysts have traditionally viewed each component individually, with a simplified attaching procedure, and generated the corresponding interface loads. This can be critical to the design details since composite components are often critical for fastener loads. Traditional analysis techniques for composite materials are a combination of simplified assumptions and empirical test data. This approach worked well when both the modeling technique for the two mating structures and the interface were of the same order of complexity. The recent increase in computational capability has allowed analysts to create very detailed finite element models of the structural components and thus make more accurate predictions of strength and stiffness, leading to more weight efficient structure. This increased fidelity of the individual component models dictates that analysis of the attaching method must also be more rigorous. In recent years the ability to model the attachment interface has been developed for both metallic and composite materials with a perceived level of accuracy. This study uses the existing analytical tools and compares those with test data to verify the accuracy of the method and provides modeling guidelines for attaining appropriately accurate results.