Project

HyOpt - Optimization-based Design of Tailored Hybrid Materials

Goal: The aim of the research project is the development of optimization-based CAE methods and flexible manufacturing processes for the design and manufacturing of load and forming compliant hybrid materials with tailored properties. Hybrid materials are defined here as a combination of fiber-reinforced plastics and thin metallic sheets. The central innovation within this project is the development of a toolbox for the design of new hybrid materials consisting of a software solution for the optimization-based design of the material structure and adaptable smart manufacturing processes for their production and further processing into lightweight components.

A material development based on a top-down approach enables the exploitation of new, as yet unused, lightweight potentials by combining conventional materials in a way that is suitable for the demands. However, the consistent transfer of the multi-material approach to the thickness and surface direction of components requires a holistic approach. In addition to the base materials, this also includes corresponding surface properties and adhesion promoter systems, ecological aspects, economic efficiency, and social acceptance.
In order to address these questions, the project also focuses on social and economic science, investigating the risk and benefit perceptions of various social stakeholder groups and analyzing the conditions under which novel hybrid materials meet with acceptance or rejection in society and the assumptions and arguments underlying these opinion-forming processes.

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Project log

Dietrich Voswinkel
added a research item
In the present study, fiber-metal laminates (FMLs) were formed by deep drawing after the metallic component was pretreated by laser structuring, sandblasting or anodizing in order to reduce the height of process-related wrinkles. Such surface texturing is commonly performed to improve the bond strength between the adhesively joined components of the FML by selectively increasing the surface area. This results in improved stability of the finished FML part due to increased resistance to delamination. First, the adhesion properties induced by each process were quantified using shear tensile tests. The shear strength was increased for all processes compared to the unstructured surface. The surface structures were characterized by roughness measurements and scanning electron micrographs. The surface properties adjusted by the different processes also contributed to the part accuracy of the deep-drawn FMLs. During forming, the matrix material contained in the unidirectional fiber composite plastic tends to build up against the forming direction, resulting in wrinkling between the flange and the cup shell. The increased adhesive strength of the metallic component impedes the flow of the matrix material and decreases the height of the resulting wrinkles. The height of the wrinkles was determined using a coordinate measuring machine on the formed FML cups.
Marcel Triebus
added a research item
Hybrid materials like fiber-metal laminates (FML) are able to lead to significant weight reduction with load adapted thickness properties. In the interdisciplinary project HyOpt, the optimization-based development of hybrid materials is researched. To ensure that the full lightweight potential of hybrid components is exploited, a holistic top-down approach is considered. Starting with the final geometry and distributed stresses an optimal material distribution can be evaluated and transformed to a semi-finished blank. Nevertheless, the formability of this optimized FML is unknown. Therefore, the formability needs to be investigated and the thickness and surface properties need to be adapted to avoid forming failures. By selecting material proportions, thicknesses and orientation angles, optima can be achieved in terms of lightweight, mechanical properties and forming characteristics.
Dietrich Voswinkel
added a research item
Laser surface treatment of metals is one option to improve their properties for adhesive bonding. In this paper, a pulsed YVO4 Laser source with a wavelength of 1064 nm and a maximum power of 25 W was utilized to increase the surface area of the steel HCT490X in order to improve its bonding properties with a carbon fibre reinforced polymer (CFRP). Investigated was the influence of the scanning speed of the laser source on the bonding properties. For this purpose, the steel surfaces were ablated at a scanning speed between 1500 and 4500 mm/s. Afterwards the components were bonded with the adhesive HexBond™ 677. After lap shear tests were carried out on the specimen, the surfaces were inspected using scanning electron microscopy (SEM). The experiments revealed that the bonding quality can be improved with a high scanning speed, even when the surface is not completely ablated.
Thomas Heggemann
added a research item
For ecological and economic reasons, the main goals in the automotive industry are the reduction of fuel consumption and the CO2 emissions of future car generations. On most cars with combustion engines produced today, the body accounts for one of the largest shares by weight, which has a leverage effect on the weight of the other vehicle components. Reducing the weight of the car body is thus very important for reducing climate-damaging CO2 emissions. Standard composites are highly advantageous in terms of their weight and mechanical properties but very cost-intensive due to the need for manual processing. A promising approach for the automated, large scale production of lightweight car structures with a high stiffness-to-weight ratio is the combination of high strength steel alloys and CFRP prepregs in a hybrid material – fiber metal laminate (FML) – which can be further processed by forming technologies such as deep drawing. FML consists of two sheet-metal top layers with a CFRP core. With this layer structure, the forming process can be simplified by comparison to the forming of standard composite material. The CFRP patches are chambered within the top layers and do not come into contact with the tool surfaces. The forming of fiber metal laminates is significantly more cost-efficient than the forming of standard composite materials. In current research being conducted by the Chair of Forming and Machining Technology (LUF) at the University of Paderborn, manufacturing processes are being developed for the production of high strength automotive structure components in fiber metal laminates. This paper presents the results of ongoing experimental and numerical research at the LUF into the forming of hybrid fiber metal laminates. The paper focuses on the dimensional accuracy of deep drawn FML-parts and the individual measures (tool, process and material design) necessary for achieving the desired part quality.
Hüseyin Sapli
added a research item
Nowadays, environment protection and thus the reduction of climate-damaging CO2 emissions has an increasing impact on the future perspective of the society. That is also the reason why the automotive industry has to generate new opportunities to reduce fuel consumption and the resulting CO2 emissions of future car generations. One way of doing this is to reduce the weight of the car. Here the use of innovative hybrid material like Fiber Metal Laminate (FML) is very promising in regard to the mechanical properties as well the economical and ecological expenses. Especially in this context, the use of FML consisting from two sheet-metal top layers and a CFRP core, e.g. of a pre-configured prepreg with a duromer matrix. Due to this special composition a very efficient processing in adapted sheet-metal-forming processes (deep-drawing) become possible where the forming and curing of the part take place. According to this, research work is presently performed at the Chair of Forming and Machining Technology (LUF) at the University of Paderborn. Aim of this work is to gain knowledge about the material and the production process and use this for the successful production of complex automotive structural components. So, the paper will present results of research work on the formability of blanks from the above mentioned special hybrid FML material under multiaxial load using spherical demonstrators with different drawing depths. A typical problem during the manufacturing of according parts is the occurrence of pronounced wrinkles and fracture. So, in regard to the prevention of wrinkling due to high tangential stresses during the forming process an adapted semi-finished part design is promising. That is why fiber scrim modifications were carried out by placing several smaller CFRP patches with different geometries (contour, length and wide) in different positions and orientations according to the acting stresses between the cover sheets. The results of research work will be discussed in comparison to the form and dimensional accuracy of deep drawn spherical hybrid components whose CFRP cores have unidirectional full-layered structures. These results prove the effectiveness of this measure.
Marcel Triebus
added a research item
Hybrid materials like fiber-metal laminates (FMLs) are able to lead to significant weight reduction with load adapted through-thickness and surface properties. In order to ensure that the full lightweight potential of hybrid components is exploited, a holistic top-down approach is considered. Starting with the final geometry and distributed stresses an optimal material distribution can be evaluated and transformed to a semi-finished blank. Nevertheless, the formability of this optimized FML is unknown, subsequently, the formability needs to be investigated and the thickness and surface properties need to be adapted to avoid forming failures. From a mathematical point of view, this is a classical multi-objective optimization problem with conflicting objective functions such as formability and lightweight factor for a given structural component. Therefore, the aim of the research project HyOpt is to obtain a purpose-built CAE method for tailor-made hybrid materials by using numerical optimization algorithms. By selecting material proportions, thicknesses and orientation angles, optima can be achieved in terms of lightweight, mechanical properties and forming characteristics. This holistic optimization routine demands basic investigations especially for suitable optimization algorithms.
Alan A. Camberg
added a project goal
The aim of the research project is the development of optimization-based CAE methods and flexible manufacturing processes for the design and manufacturing of load and forming compliant hybrid materials with tailored properties. Hybrid materials are defined here as a combination of fiber-reinforced plastics and thin metallic sheets. The central innovation within this project is the development of a toolbox for the design of new hybrid materials consisting of a software solution for the optimization-based design of the material structure and adaptable smart manufacturing processes for their production and further processing into lightweight components.
A material development based on a top-down approach enables the exploitation of new, as yet unused, lightweight potentials by combining conventional materials in a way that is suitable for the demands. However, the consistent transfer of the multi-material approach to the thickness and surface direction of components requires a holistic approach. In addition to the base materials, this also includes corresponding surface properties and adhesion promoter systems, ecological aspects, economic efficiency, and social acceptance.
In order to address these questions, the project also focuses on social and economic science, investigating the risk and benefit perceptions of various social stakeholder groups and analyzing the conditions under which novel hybrid materials meet with acceptance or rejection in society and the assumptions and arguments underlying these opinion-forming processes.