Project group C: Design of hybrid lightweight structures

Multi-axial textile reinforced composites with thermoplastic matrices offer high potentials for a rapid manufacturing of components with a load-adapted property profile. The development of corresponding material models as well as an extensive experimental material characterisation forms the foundation for the design of such complex lightweight structures. The application of these new textile-reinforced materials in lightweight structures requires not only the knowledge of the quasi-static material behaviour but also a material characterisation under complex operating loads and environmental effects.

For the improvement of the developed material degradation models, the influence of process-related parameters from the textile processing and the composite manufacture needs to be identified. These effects are to be considered by means of suitable probabilistic approaches in subproject C1. Additionally, the influence of superimposed thermal loadings on the material behaviour will be investigated experimentally. Beyond these tests, experimental and theoretical investigations regarding the fracture-mode-related fatigue behaviour under tension/compression-torsion loads are planned for the novel textile composites.

The investigation of the mechanical behaviour of textile-reinforced composites with thermoplastic matrices under dynamic loading (subproject C4) is required for the improvement of the material models developed in the first phase. The strain-rate-dependent material behaviour under out-of-plane loads as well as on the structural behaviour of curved composite components and on textile-adapted joining elements are studied in order to improve the developed material models in terms of 3D stress, deformation, failure and damage analysis.

In addition to phenomenological material models, multi-scale modelling and simulation techniques are considered in subproject C2. Starting from the physical properties of micro- and mesoscale, the effective macroscopic linear elastic stiffness of textile-reinforced materials and spacer-fabric structures has been computed using homogenization techniques based on the analysis of a representative volume element (RVE) entirely typical for the internal material structure. In the second project phase, the results obtained so far will be enhanced in order to take nonlinearities into account. Attention is drawn to the formulation of constitutive laws for the nonlinear material behaviour of matrix and fibres as well as to nonlinear homogenization techniques.

Motivated by the future structural applications and demonstrators, nonlinear constitutive equations, modelling procedures and homogenization techniques have to be merged in an adaptive multi-scale simulation forming the basis for the development and design of a generic technology demonstrator for the proposed function-integrating multi-material design in the third research phase.