A. Hornig

An Experimental Method for Dynamic Delamination Analysis of Composite Materials by Impact Bending

An improved experimental method for characterizing dynamic delamination growth in composite structures has been developed and verified using high speed photography and explicit finite element simulation. The method is based on a three-point bending device. End notch flexure carbon fiber composite beam specimens were subjected to both quasi-static and impact rates of Mode II loading. The experimental results showed no significant strain rate dependency of the delamination fracture toughness. This important result complements the scarce and conflicting data available in the literature, and serves as a reference for calibration of numerical modeling strategies.

Thermoactivated Pinning - A Novel Joining Technique for Thermoplastic Composites

Due to their good mechanical properties and short cycle times during processing, textile-reinforced thermoplastic composites gain increasing relevance for high-volume lightweight applications. Beyond that, by exploiting its specific processing capabilities, this composite material enables a variety of novel manufacturing techniques, e.g. for assembling. In this paper a joining technique is presented, which utilises the meltability of the thermoplastic matrix to establish a material-adapted joining method by introducing slender metallic pins into the composite structure. The processing principle is described and structural effects in the joining zone are analysed by means of microscopy. The load bearing behaviour is characterised by tensile tests on double-lap-shear specimen.

On the Reduction of the Pre-Processing Effort and the Application of a Contact Meshing Approach for Complex Jet Engine Component Assemblies

A significant proportion of the work effort for finite element (FE) analysis is spent for pre-processing activities, especially for complex structural components and component assemblies. An exclusive use of hexahedron (hex) elements increases the meshing effort substantially compared to tetrahedral elements. An automated method to generate high quality hexahedral meshes for an arbitrary geometry does not exist. In this work, commercially available FE software tools for meshing were investigated with the focus on an advantageous pre-processing effort. The evaluation showed that the software package NX (Siemens PLM Software) offers robust advanced semiautomatic hex meshing capabilities.Furthermore, a Contact Meshing Approach (CMA) was elaborated to reduce the effort of the challenging and time-consuming geometry decomposition significantly. Using the example of an intermediate pressure compressor it can be shown that the pre-processing effort time can be reduced up to 75%. Due to the independent meshes, element transitions in the geometry become redundant. This results in lower total element numbers and higher mesh qualities and subsequently leads to more efficient calculations. Moreover, the increased element quality has positive effects on the result quality.Copyright

Characterising the thermoforming behaviour of glass fibre textile reinforced thermoplastic composite materials

Textile reinforced thermoplastic composites are predestined for highly automated medium- and high-volume production processes. The presented work focusses on experimental studies of different types of glass fibre reinforced polypropylene (GF-PP) semi-finished thermoplastic textiles to characterise the forming behaviour. The main deformation modes fabric shear, tension, thought-thickness compression and bending are investigated with special emphasis on the impact of the textile structure, the deformation temperature and rate dependency. The understanding of the fundamental forming behaviour is required to allow FEM based assessment and improvement of thermoforming process chains.Textile reinforced thermoplastic composites are predestined for highly automated medium- and high-volume production processes. The presented work focusses on experimental studies of different types of glass fibre reinforced polypropylene (GF-PP) semi-finished thermoplastic textiles to characterise the forming behaviour. The main deformation modes fabric shear, tension, thought-thickness compression and bending are investigated with special emphasis on the impact of the textile structure, the deformation temperature and rate dependency. The understanding of the fundamental forming behaviour is required to allow FEM based assessment and improvement of thermoforming process chains.

Forming of carbon fiber reinforced thermoplastic composite tubes - Experimental and numerical approaches

Continuous-reinforced thermoplastic composites are of growing importance for series production of lightweight components in manifold industrial areas. Novel manufacturing technologies allow the production of hollow semi-finished products that are post formed to enhance functionality. To maximize efficiency in the development process of such components it is necessary to map the forming processes numerically using Finite Elements(FE)-methods. The aim is to perform feasibility studies at an early stage, reduce development time by virtual process optimization and to generate a detailed understanding of the post formed fiber architecture for further structural-mechanical analysis.

On the Development of Strategies for an Efficient Semi-Automated Hex-Meshing Process of Complex Jet Engine Component Assemblies

A significant proportion of the work effort for a whole engine analysis is spent for prep-processing tasks especially for component assemblies and complex structural components. With respect to the generation of a pure hexahedral mesh, the work effort increases due to the absence of an automatic method to generate high quality hexahedral meshes for an arbitrary geometry. In addition, the time-consuming hexahedral meshing process contains numerous, repetitive tasks for large and complex assemblies due to similar and identical components.In this work a modular strategy for hexahedral meshing of large and complex assemblies was explored with the aim to reduce and to simplify the development process due to a prospective semi-automation of time-consuming routines. The procedure bases on an initial identification and classification of each component of the whole assembly regarding e.g. overall meshing complexity. Meshing relevant parameters were identified for geometry preparation and hexahedral meshing itself. Furthermore, for semi-automation the software package NX (Siemens NX Software), in particular the incorporated automation tool Product Template Studio (PTS) was investigated which enables an automated re-meshing of the geometry model in case of design changes.Copyright

On the quantification of errors of a pre-processing effort reducing contact meshing approach

The generation of a suitable all-hexahedral (all-hex) meshed model of a specific design model is one of the main tasks within the pre-processing for creating the analysis model. In contrast to tetrahedral meshing, all-hex meshing requires additional preparation of the geometry for mesh generation due to the absence of a robust and reliable automatic hex meshing algorithm [1]. The usage of all-hex meshes is motivated by the fact that they mostly contain fewer nodes and elements than all-tetrahedral meshes at similar or even higher result quality. Besides, the mesh locking effect is still a serious shortcoming of linear tetrahedral elements [2-3]. The usage of quadratic tetrahedral elements with less mesh locking issues is often not recommendable due to the required higher computational effort. Therefore, the development of a general-purpose all-hex mesh generation procedure is in the focus of the research community since a long time. Promising progress has been made recently in the field of automatic hex mesh generation for specific problem cases [4-7] and great potential to improve the overall pre-processing efficiency show Knowledge Based Engineering (KBE) tools [8]. The problem, however, is that there is no approach which is able to automatically mesh complex assemblies with all-hex meshes as it is required for large complex simulations. Therefore a method has been developed which will be discussed in this paper in more details. The procedure to generate an all-hex meshed model can be classified in two main approaches. The mesh-first approach creates a finite element mesh which is subsequently modified and transferred on a geometrical model. In contrast, the geometryfirst approach creates the mesh through filling the geometric representation of the model with finite elements using model boundary framework. In this work, a Contact Meshing Approach is presented for the pre-processing