Schwingbruchstrukturen an faserverstärkten Kunststoffen

Structures of Fatigue Fractures in Fibre-Reinforced Plastics The report deals with macrofractographic and microfractographic structures in non-reinforced epoxide resins as well as in glass-fibre reinforced plastics and carbon-fibre reinforced plastics after fatigue stresses. Epoxide resins show fatigue striations and fracture lines similar to those in metals. The distance between the fatigue striations amounts to between 0.70 and 150 m?m and increases continuously in the direction of fracture propagation. The instantaneous fractures in non-reinforced resin show parabolic cusps besides Wallner-lines and lance-shaped structures. Surfaces of delamination fractures of glass-fibre reinforced plastics show fatigue striations which are characteristic for fibre-reinforced composites, but their morphology differs from the fatigue striations in non-reinforced resin. This was the first time that fatigue striations could be discovered in fibre-reinforced composites of a fibre content of 70 per cent by volume. These fatigue striations are strongly marked at the positions of the fibres and will probably arise only in case of a sufficiently high local stress intensity. Moreover, the amounts of the local slicing and shearing stress components, of which is composed the stress causing the fracture, could be partly responsible for the formation of fatigue striations. The formation of the fatigue striations allows to draw conclusions with respect to the fracture-causing local stress distribution and the local crack propagation in fibre-reinforced plastics. The surfaces of instantaneous fractures in glass-fibre reinforced plastics and carbon-fibre reinforced plastics show parabolic cusps. This is another distinguishing characteristic as compared with the surfaces of fatigue fractures.     

Management of new technologies in production and logistics

The increase of a company's competitiveness can be compared with the acceleration of a train. In this idea the product is represented by the tractive power of the locomotive and the production system by the waggons. Until now, a powerful locomotive was considered to be the most important condition of success, which means an excellent product, leading all waggons: production, logistics and organization. Worlwide, it can be observed that even feeble locomotives (products) with easily running waggons are overtaking powerful locomotives with heavily running waggons. This requires a concentration on the speed of the whole train, taking all influencing parameters into account. The enterprise's investment strategy demonstrates an almost equal percentage of its investable funds, namely about 5% of the return for research and development and about 6% for new technologies. The share of new technologies in production is increased from 62 to 68%.The strategic potential of new technologies in production and logistics can be judged by their effects on critical factors for success like costs, quality, flexibility and time. The achievable advantages in competition depend on the level of experience and on the duration of protection against imitation, as well as on the turnover and market shares of the products involved.To align an enterprise with the critical factors of success, the exclusive use of new technologies for automation is not sufficient. The combination of productive factors has to be rearranged frequently. Existing organizational structures, potential of employees, systems of logistics and technologies of production have to be improved considering these circumstances. They should be integratively controlled in a long-term strategy through the systematic management of technology.     

Nickel-iron catalysts prepared by homogeneous deposition-precipitation of cyanide complexes on a titania support

Nickel-iron catalysts have been prepared by homogeneous deposition-precipitation of complex nickel-iron cyanides on a titania support. The nickel-iron alloys obtained after calcination and reduction of the cyanide precursors were characterized by Mössbauer spectroscopy, high-temperature X-ray diffraction, and magnetic measurements. Fischer-Tropsch experiments show remarkable results. Catalysts prepared from K₃Fe(CN)₆ and Na₂Fe(CN)₅NO cyanide precursors exhibit a high activity and selectivity, whereas catalysts prepared from K₄Fe(CN)₆ do not show any activity. This lack of activity is caused by the presence of potassium in catalysts prepared from K₄Fe(CN)₆. Potassium or iron titanate inhibits the adsorption of CO on the nickel-iron surface. Deactivation of active nickel-iron catalysts was caused by the deposition of inactive carbon during Fischer-Tropsch synthesis.     

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