Andreas Todt

Development and Characterisation of Phenolic Resin Moulding Materials for the Production of New Short Fibre-Reinforced C/C-SiC Composites

This article focuses on the development of phenolic resin moulding materials for the production of new carbon fibre-reinforced ceramic composite materials based on C/C-SiC by utilising the LSI (liquid silicon infiltration) production method. The production of these moulding materials is being accomplished by combining phenolic resin and carbon fibres with the addition of a few selected parts of processing aids, during which the influence of the used lubricants on the processability of the moulding materials is examined. The starting materials, microstructures and mechanical properties of the materials were characterised at every step of the entire process (CFRP and C/C composites) as well as the end of the whole production (C/C-SiC composites). During this investigation a link between the portions of the lubricant used, the forming of the porosity and the impact on the mechanical properties was discovered. In regards to the optimisation of the process the involved parties were able to determine an optimal lubricant ratio.

An innovative production method for a C/C-SiC brake disc, suitable for a large-scale production

The industrial progress and the market-oriented management concepts result in increasing demands of the industry for improved performances while simultaneously improving on the energy efficiency. This results in the necessity for a progressive implementation of high-performance materials in areas such as the automotive industry, engineering, as well as applications in aerospace industry. Especially construction elements taking on large stresses call for excellent mechanical properties even at extremely high temperatures. In these high-temperature ranges only engineering ceramics, which unfortunately are very limited regarding the application due to the very brittle characteristics, showcase sufficient strength values.

New approach to design of ceramic/polymer material compounds

The damage tolerance of carbon fibre-reinforced ceramic-matrix composite materials depends on their porosity and can be rather significant. Complex structures are difficult to produce. The integration of simple geometric structures of ceramic-matrix composite materials in complex polymer-based hybrid structures is a possible approach of realising those structures. These hybrid material compounds, produced in a cost-efficient way, combine the different advantages of the individual components in one hybrid material compound. In addition the individual parts can be designed to fit a specific application and the resulting forces. All these different advantages result in a significant reduction of not only the production costs and the production time, but also opens up new areas of application, such as the large-scale production of wear-resistant and chemically inert, energy dampening components for reactors or in areas of medicine. The low wettability of the ceramic component however is a disadvantage of this approach. During the course of this contribution, different C/C composite materials with a specific porosity were produced, while adjusting the resin/hardening agent-ratio, as well as the processing parameters. After the production, different penetration tests were conducted with a polymer component. The final part of the article is comprised of the microstructural analysis and the explanation of the mechanical relationships.

Fundamental Studies and Development on an Innovative Ceramic/Polymer Material Compound

Fibre-reinforced ceramic composite materials offer excellent thermal, mechanical and chemical properties. Due to their intrinsic fibre structure and porosity, they offer a great damage tolerance. Therefore, they provide superb attenuation characteristics, as do polymer composites. The current compound systems consisting of ceramic components feature a rather low capacity for energy absorption in relation to their weight; this is a fact in dire need of a fundamental change. In regards to the development of new hybrid ceramic/polymer material compounds basic research of the material design and binding behaviour of the different components is necessary. The advantage of this development allows for a selective implementation of positive characteristics of one component in an integrated compound-system. This opens up completely new possible are-as of application, such as wear and tear resistant and chemically inert, energy absorbing elements for the construction of reactors or areas of medical technology. During the investigation, a few selected fibre-reinforced ceramic composite materials with a specific porosity were produced, while adjusting the amount of resin/hardening agent used, as well as modifying other parameters. This was followed by tests regarding the wetting with a polyurethane component. The characterisation and analysis of the hybrid compounds on a microscopic scale is achieved by means of optical microscopic examinations. The characterisation of the mechanical attenuation characteristics on the other hand is realised by means of DM(T)A. The flexural strength is determined by utilising a “three-point-bending test”.

Influence of Hardener Content and Curing Parameters on the Microstructure and Mechanical Properties of Porous C/C Composites

Carbon fibre reinforced carbon composites (C/C) are characterised by their excellent thermal, chemical and mechanical properties. The intrinsic porosity and fibre reinforcement grant them an excellent damage tolerance. The production of complex structures is time consuming and very expensive. An innovative approach to this topic is the integration of simple geometric ceramic composite materials within complex polymer structures. The motivation of this contribution is to investigate the influence of hexamethylenetetramine as hardener (hardener content: 4, 8, 12 and 16 %) and curing parameters (tempered and non-tempered) on the microstructure and mechanical properties of the porous C/C composites. During the course of this contribution, selected carbon fibre reinforced polymer (CFRP) composites with different porosities were produced while adjusting the resin or hardening agent-ratio, as well as the processing parameters. Subsequent to the curing of the CFRP samples, porous C/C composites were produced by means of a pyrolysis process. The final part of the contribution is comprised of the microstructural analysis by light microscopy and the explanation of the flexural strengths, by utilising a “three-point-bending test”.

Großserientaugliche Formgebung durch Duroplast-Spritzgießen zur Herstellung von faserverstärkter Keramik

KurzfassungIn gemeinsamer Kooperation der Professuren Verbundwerkstoffe (Prof. G. Wagner), Strukturleichtbau und Kunststoffverarbeitung (Prof. L. Kroll) sowie Polymerchemie (Prof. S. Spange) der Technischen Universität Chemnitz wurde ein großserientaugliches Formgebungsverfahren zur Herstellung faserverstärkter C/C-SiC-Verbunde entwickelt. Das Verfahren wird die Produktionskosten erheblich senken.AbstractIn joint cooperation of the departments of composite materials (Prof. G. Wagner), lightweight structures and polymer technology (Prof. L. Kroll), and polymer chemistry (Prof. S. Spange) of Technische Universität Chemnitz a process suitable for large-scale production of fibre-reinforced C/C-SiC composites has been developed. This process will significantly reduce the production costs.