Heinz Voggenreiter

Analysis of Crushing Response of Composite Crashworthy Structures

The paper describes quasi-static and dynamic tests to characterise the energy absorption properties of polymer composite crash energy absorbing segment elements under axial loads. Detailed computer tomography scans of failed specimens are used to identify local compression crush failure mechanisms at the crush front. The varied crushing morphology between the compression strain rates identified in this paper is observed to be due to the differences in the response modes and mechanical properties of the strain dependent epoxy matrix. The importance of understanding the role of strain rate effects in composite crash energy absorbing structures is highlighted in this paper.

Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.

Thermoplastic Forming as an Alternative ShapingProcess for Near-Net-Shape Production of C-SiSiCCeramics via Liquid Silicon Infiltration (LSI) Process

The present study demonstrated the feasibility of producing carbon-based green bodies by means of extrusion, pyrolysis and subsequent conversion to C-SiSiC ceramics according to the LSI process.Athermoplastic binder system was used for the development of feedstocks that differ from conventional duroplastic binder systems as these would have created difficulties during processing owing to their curing behavior. Activated carbon, carbon fibers and semicoke were used as fillers and a source of a sufficiently stable carbon backbone in the carbonized intermediate. Special attentionwaspaid to the characterizationandquantification of material behavior at the water debinding step as well as at thermal treatment during pyrolysis. Porosity and microstructural characteristics of carbon bodies and subsequent C-SiSiC microstructure after Si-infiltration were investigated by means of scanning electron microscopy and porosity measurements.Thefeasibility of producing carbon-based extrusion feedstocks with high homogeneityandflowability which can be converted into SiC by means of LSI shows that the concept may be applied to production of near-netshape C-SiSiC components by means of thermoplastic injection molding

The Effect of Impact on the TiAl Alloy TNBV3B Produced on Three Different Processing Routes

The impact behaviour of the TiAl alloy TNBV3B produced on three different processing routes - cast, forged (with a relatively small degree of deformation) and extruded - has been studied making use of ballistic tests. The damage evolution due to centre and edge impacts on flat and airfoil-like specimens has been investigated with a focus on the influence of the microstructure. Apart from the influence of material properties, the impact location showed a strong effect on the damage evolution. The extension of impact cracks in the interior of the specimens has been studied making use of heat tinting experiments and computer tomography analyses.