Simulation-driven design of bonded joints in fibre composite aircraft structures using progressive damage analyses

Abstract

In fibre composite structures, bonded joints offer mechanical advantages over bolted joints and can thus contribute to lightweight design. Nevertheless, in aircraft constructions most joints use mechanical fastening elements. One of the major obstacles to the use of bonded joints is the complexity of the design task. In addition to the simple strength requirement, a specific failure mode of the joint is required. A so-called stock-break failure in the composite adherend is desired. In order to facilitate design and certification, a simulation-based determination of the failure behaviour is aimed at. For this purpose, a holistic but pragmatic approach for the progressive damage analysis of the entire bonded joint is compiled. This holistic approach includes the material behaviour of the fibre composite adherends, i.e. the intra- and interlaminar behaviour, as well as the mechanical behaviour of the adhesive including plasticity and damage. For each component different modelling approaches, varying in complexity and accuracy, are under investigation. In order to test the compiled approaches, the required material parameters are determined experimentally within the scope of this work. To demonstrate the potential of the approach, it is applied to derive a design guideline for the required positioning accuracy of a bonded longitudinal fuselage joint.