Materials Science Forum Vols. 825-826

Abstract: In this study, the reinforcement of bio-based Polyamide 11 (PA 11) with physico-chemically modified Beech Fibers was investigated. In a first step, an improvement of the thermal stability of the fibers was achieved by a two-step alkaline treatment with sodium hydroxide and hydrogen peroxide. This effect was attributed to the removal of the hemicellulose from the fiber surface, as verified by Attenuated Total Reflection Infrared Spectroscopy (ATR-FTIR). Consequently, the onset-temperature of thermal degradation as measured by Thermo-Gravimetric Analysis (TGA) increased from 285 °C to 337 °C. Given this, the compounding of the modified fibers with the low melting bio-based Polyamide 11 was done in a lab-scale co-kneader and followed by subsequent injection molding of test specimens. Analysis of the mechanical and thermo-mechanical properties of the processed Wood Plastic Composites showed a beneficial effect of the chemical fiber treatment on composite stiffness, and allowed for suggestions to improve the up scaling of the processing.

Abstract: Modified wood fibre reinforced polypropylene composites at a wood fibre content of 50 wt. % are prepared using different types of wood fibres (beech wood refiner fibre, mercerised beech wood refiner fibre, mercerised and bleached beech wood refiner fibre as well as beech wood chips, mercerised beech wood chips, mercerised and bleached beech wood chips) to improve the impact resistance of the final composite. Additionally a beech wood refiner fibre-PP composite as well as a beech wood chip-PP composite are mixed with regenerated cellulosic fibres (5 wt. % and 10 wt. %) to further enhance the impact resistance. To increase the interfacial adhesion with the matrix and to improve the dispersion of particles two different coupling agents with contents from 2 wt. % to 8 wt. % are tested with two wood plastic composites (WPC). One is made of beech wood refiner fibres and the other one is produced from beech wood chips.The present study investigated Charpy impact property of wood fibres reinforced polypropylene as a function of fibre modification, content of regenerated cellulosic fibres and coupling agent.From the results it is observed that beech wood refiner fibre-PP composites show better Charpy impact properties than beech wood chips-PP composites. Charpy impact resistance is improved by mixing regenerated cellulose fibres (RCF) and RCF-PP-granule with beech wood refiner fibres and chips. The maximum increase in impact resistance is two times for refiner fibres and 10 % RCF-PP-granule respectively three and a half times for chips and 10 % RCF-PP-granule. By adding coupling agent Charpy impact resistance is nearly doubled for all wood fibre-PP composites.

Abstract: The development of new biocomposites and efficient manufacturing methods that are suitable for series processing is the purpose of the current sub-project C4 of the Excellence Cluster MERGE, sponsored by DFG (Deutsche Forschungsgemeinschaft). Two different types of materials are combined: bio-based thermoplastic polymers such as bio-polyethylenes or bio-polyamides and renewable reinforcing materials such as thin wood veneer or unidirectional flax fibers. To achieve a high-efficiency in terms of mass-production, reproducibility and flexibility, it is required to perform several steps in the realization of semi-finished and final products. The improvement of the adhesion at the interface of the components, the implementation of continuous processes, in order to increase energetically the yielding, and the final design, through several methods, for future potential applications are so many perspectives to achieve.

Abstract: Loose hierarchical flax fibres/polypropylene composites were manufactured in a simple way based on a paper-making process in order to include nanocellulose and allow the hornification of the nanofibres in a controlled manner. The effect of flax fibre content on the flax/polypropylene composites and the influence of nanocellulose on the properties of these composites are discussed. By increasing the flax content a slight decrease of the tensile strength and an increase of the Young´s modulus were observed. On the other hand, no significant effect was noticed when increasing the bacterial cellulose content in the composites.

Abstract: The necessary thermal insulation for buildings was provided for years optimally by polymer foams. Generally the foam is based on petrochemical resources. It is used for external wall insulation and not employed for additional functions. A Sandwich build of rigid laminates and a quite shear resistant polymer foam core results in an extraordinary stiff element. This provides thermal insulation and forms an independent load carrying structure. The sustainability of the sandwich structure can be raised by combining materials from renewable resources. The sandwich system currently developed, in cooperation with our partner from industries C3 Technologies, consists of lignin based foams of varying density and natural fibre reinforced laminates. The lignin is produced from beech-wood via the organosolv-process. Afterwards it is chemically integrated into the phenolic resin. The proportion of lignin in the resin can be varied from 10% up to 40%. This poses a quite prospective idea since using lignin means using nature’s own synthesis instead of artificial petrochemical processes for resin production and thus reducing the energy needed for resin production

Abstract: Materials and their properties are nowadays mostly represented either in forms of material data bases or digital data sheets. While these are sources of facts about the particular materials, the interconnection between the different materials, their usage and development is still lacking. Besides, the data bases are mostly distributed, run by different institutions or specialized on only one category like metals or polymers. The given article addresses the application of knowledge management in the area of material science and engineering for gathering, representing and distributing knowledge as well as supporting a sustainable material and product development. Sustainability, green engineering and innovativeness are crucial deciding factors for today’s material development and should therefore be addressed and integrated in the scope of promoting innovation in material science. To accomplish the aforementioned goal, a combination of semantic and case based methods will be applied in a holistic concept, entitled MatProSQI. It is thus become possible to interconnect and reference fact or knowledge of materials, like category, property, test results, production requirements, sustainability factors, user feedback and experiences of former applications. In addition to the representation of knowledge, collaboration between the engineers is detected as an essential factor for a steady transfer of knowledge.

Abstract: This study summarizes different characterisation methods performed with new carbon fibres(vCF - virgin carbon fibres) for structural applications as carbon fiber reinforced plastic (CFRP)as well as fiber samples which have been treated under different conditions. These parameters consistof combinations of temperature (400-600 C) and dwell time (30 - 60 min) in an oxidising atmospherein order to provide a fundamental basis for the definition of possible recycling processes to regain thehigh value raw material, i.e. the carbon fibre, after the use-phase of the initial CFRP-structure. The investigationsthat were performed on vCF and secondary fibres (rCF - recycled CF) show in very goodagreement, that below 500 C almost no degradation of the fibre is visible, between 500 and 600 C arapid decrease in different physical and mechanical properties occurs and above 600 C a recovery ofthe fiber in terms of a secondary use in high performance structural context seems not to be feasible.The investigations that were performed consist of optical microscopy for the measurement of the fibrediameter, the deformation of the cross section and a statistical analysis. The second method appliedwas the characterization of the monofilament density, alongside to the breaking force and elongation,leading to the calculation of tensile strength and Youngs Modulus and further statistical analysis ofWeibull Modulus and its decrease over temperature.

Abstract: This thesis investigates the development of an innovative fibre reinforced composite. A developed textile, consisting of mineral fibres that is embedded in a special mastic asphalt matrix. The integration of a grid shaped textile structure into the asphalt cause an inner reinforcement of the asphalt layer. This leads to a significant enhancement towards the tensile strength during bending. It also gives resistance to deformation. Rut formation is minimized and the thickness of the asphalt layer can be reduced.