LISA (Lightweight Integral Structures for Future Generation Aircrafts)
LISA is a project demonstrating the capabilities of the ACE platform in the Materials Mechanics group of the Institute of Materials Research. Within this project a joint of an Aluminium fuselage sheet with a stringer shall be produced, tested, simulated and optimized. The task is conducted in cooperation with EMBRAER, the 4th largest Aircraft manufacturer in the world.
The main objectives of this project are:
• Introduction of new skin/stringer joint configurations
• Use of new joining technologies for fuselage manufacturing: Laser Welding and Friction Stir Welding
• Investigation of the performance of future skin/stringer configurations under monotonous loading (residual strength) and fatigue loading (damage tolerance).
• Comparison with existing riveted structures
• Optimization with respect to safety and productivity
In the simulation department, the damage and failure of the stiffened panels are simulated under monotonous loading. While conventional plasticity models are used for the deformation behaviour of the Aluminium, a cohesive zone model is adopted for the damage behaviour. Parameters for the numerical models are retrieved from simple tests for the base materials, and from small scale tests for the properties of the weldments. The behaviour of welded structures will be predicted.
SFB 986 M3 (multiscale tailor-made material systems)
The long-term research goal of the Collaborative Research Center “SFB 986: Tailor-Made Multi-Scale Materials Systems – M3“ is to develop experimental methods for producing and characterizing multi-scale structured materials with tailor-made mechanical, electrical, and photonic characteristics. It has been approved by the German Research Foundation (DFG) under the leadership of TUHH in close collaboration with the University of Hamburg and the Helmholtz-Zentrum Hereon. Within the SFB 986, 20 project leading scientists work on a cross-disciplinary approach to develop completely new types of materials. The department is taking part in a project that belongs to the project area A “Quasi-self-similar hierarchical materials systems”: the project A5, called “Multi-scale modeling of material failure”.
The macroscopic behaviour of materials is defined by their underlying microstructure. So-called multi-scale models are established nowadays for continuous processes (in space and time), but for discontinuous processes such as those associated with material failure in the form of cracks or shear bands, the scale-bridging and homogenization of material properties is still a challenge. These issues play a significant role within the scope of the SFB 986. Therefore, the project A5, aims at the development of new methods for the multi-scale modeling of such processes.
These advanced multi-scale descriptions would thus be able to provide a uniform description of both continuous and discontinuous processes. They would therefore be able to predict the influence of the microstructure, as for instance the shape and distribution of hard particles in a polymer matrix, on the macroscopic continuous deformation behaviour (before crack formation). Beyond that, they would also allow the analysis of the quantitative impact of micro-cracks in macroscopic material failure. For the reasons mentioned above, these advanced methods are absolutely vital for a knowledge-based development of microstructures which lead to improved macroscopic properties such as high macroscopic strength properties and high crack resistance.
Nano scaled hierarchical microstructure of enamel
Bovine dental enamel exhibits a complicated fibrous hierarchical microstructure and with particular mechanical properties on each size scale. The primary aim of this project is to establish a computational model for each hierarchy level and to simulate the mechanical properties of the dental enamel in order to understand the benefits of the hierarchy and eventually optimize the design of hierarchical material systems.
• Development of a computational model that can describe the mechanical characteristics of a hierarchical material
• Numerical modeling and prediction of mechanical properties of enamel at various hierarchy levels
• Investigation of how different hierarchies of dental enamel affect and interact each other
• Understanding the relationship between hierarchical arrangement and mechanical properties
• Optimization and improvement of the mechanical properties of the macroscopic material by adopting hierarchical structure design
Micromechanical modeling of fully lamellar TiAl at elevated temperatures
Fully lamellar titanium aluminide (TiAL) alloys exhibit a beneficial combination of good thermomechanical properties with a low density and are therefore increasingly used as structural materials for high temperature lightweight applications like, e.g., low-pressure turbine blades in aircraft engines. Their outstanding macroscopic mechanical properties originate from the lamellar microstructure with its various internal boundaries. This microstructure shows a complex micromechanical behavior, rendering the prediction of the macroscopic materials behavior complicated if not impossible with the use of conventional constitutive material models.
In this project, we set up a temperature-dependent micromechanical constitutive material model which is able to predict the plastic deformation behavior of lamellar TiAl alloys.