Title:	Experiments and Modelling of Composite-Aluminium Bolted Joints
DNr:	NAISS 2024/22-1673
Project Type:	NAISS Small Compute
Principal Investigator:	Hannes Wemming <hannes.wemming@liu.se>
Affiliation:	Linköpings universitet
Duration:	2024-12-18 – 2026-01-01
Classification:	20302
Keywords:

Abstract

Aircraft structures typically consist of numerous components joined using mechanical fasteners, which are often weak points in the airframe. Ensuring joint strength and overall structural integrity is essential for flight safety and airworthiness. Achieving this, while avoiding a significant weight penalty, requires accurate dimensioning. Current finite element (FE) methods lack efficient and accurate ways to represent fasteners in large structures due to their complex mechanical behavior. This project aims to develop a numerically efficient method for modeling the mechanical behavior of bolted joints in a simplified yet accurate manner. The mechanical behavior of composite/aluminum bolted joints will be characterized through physical experiments and detailed FE simulations, see previous published works [1, 2, 3] and Licentiate thesis [4]. The results will guide the development of simplified bolted joint representations, which will be validated against experimental data. While solid 3D FE models can capture local effects like bearing failure, frictional contact, and preload, they are computationally expensive and impractical for large structures. Simplified models from earlier research, though efficient, fail to account for key local phenomena, compromising accuracy. This project seeks to bridge this gap by developing a modeling approach that balances efficiency and accuracy, enabling the simulation of structures with numerous fasteners. The project’s main activities include calibrating detailed FE models with experimental data, conducting parameter studies to evaluate stiffness and strength, and deriving simplified model parameters. These developments will enable cost-effective and accurate simulations of large airframe structures, supporting structural integrity. The aerospace industry will benefit directly from weight-efficient and cost-effective design methods. Improved modeling accuracy will reduce material usage, enhance structural performance, and decrease reliance on expensive and time-consuming physical testing. Furthermore, the project supports sustainability goals by enabling lighter aircraft structures, reducing CO₂ emissions, and promoting efficient material use. By advancing numerical simulation capabilities for bolted joints, this research strengthens the aerospace academic and industrial sectors, enabling the design of weight-efficient structures and contributing to the progression of digital design techniques. [ 1 ] Wemming H, Lindström SB, Johansson L, Kapidžić Z. Identification of bearing failure in composite-aluminium bolted joints using digital image correlation. Composite Structures, Volume 300, 116072, 2022. [ 2 ] Wemming H, Lindström SB, Johansson L, Kapidžić Z. Modelling and experimental parameter identification for fasteners in composite–aluminium bolted structures. Composite Structures, Volume 323, 117464, 2023. [ 3 ] Lindström SB, Wemming H, Kapidžić Z, Loukil MS, Segersäll M. Integrated digital image correlation for mechanical characterization of carbon fiber-reinforced polymer plates. Composite Structures, Volume 305, 116501, 2022. [ 4 ] Wemming H. Experiments and Modelling of Composite–Aluminium Bolted Joints. Linköping Studies in Science and Technology, Licentiate Thesis No. 1945, Linköping University, 2022.