Manufacture and test of composite tube specimens with braided glass fiber reinforced
Wojciech Błażejewski*, Werner Hufenbach**, Andrzej Czulak**, Robert Bohm** *Politechnika Wrocławska, Instytut Materiałoznawstwa i Mechaniki Technicznej, ul. Smoluchowskiego 25, 50-370 Wrocław **Technische Universität Dresden, Institut für Leichtbau und Kunststofftechnik, Dürerstraße 26, D-01062 Dresden
Quarterly No. 4, 2005 pages 67-71
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abstract The reinforced composites offer a - not jet utilized - lightweight potential for innovative lightweight applications. One of the most frequent occurring problems in the design of composites structures with textile reinforcement is the determination of directional mechanical properties of composite materials. Here, the material characteristics of matrix material and fibers given by manufacturer are not helpful in the design process, because of different manner of treatment used during manufacturing by various producers. Thus, before the design and realization of a composite prototype structure it is necessary to conduct experiments in order to valuate the composites materials properties. Here, it is important to use the same production technique in preparing the samples as in the prototype manufacture, so that the manufacture influence can be assessed. The determination of strength related properties and a subsequent failure analysis of reinforced composites require advanced tests under uni-axial and multiaxial loading conditions. In the production process of composite tubular samples the composite material is put onto the cylindrical core (diameter: 40 mm), using winding or woven sleeves methods. The basic method of production of tube specimens, is showed in Figures 2 and 3. In the next step various finishing techniques have been tested for removing the resin overflow, air includes and flattening of impregnated fibre layers, achieving a smooth and homogenous outer surface. The chosen technique should be optimal in consideration of repeatability and costs of production. The basic method of various finishing techniques of tube specimens, is showed in Figures 4 and 5. Here, the tests pressure was achieved by the use of rubber as working medium. A heap of cylindrical rubber blocks with a height of 100 mm was put into the pipe. This heap was compressed bilaterally by steel pushers fixed in clamped support of tension testing machine (Fig. 6). During this investigation the size of dislocation of rammers and increase of the compression force was recorded. Acoustic emission and the size of dislocation were the parameters of the destruction level of the composite material. It was recognized, that investigation of the strength torsion, tension, compression, internal pressure (as well as combination of mentioned) on used tubular samples have the smallest mistake consequential from preciseness of realization of the samples, because of the specific mechanical processing (e.g. cut), the kind of load etc. Within the manufacture process the best finishing techniques is the wrapping around with textile tape. This technology assures the good extraction of excess of impregnate, extraction of the air includes, flattening the layers of composite. The comparison of the investigation methods, depending on the pressure of rubber inside of tubular sample, is satisfying using selected techniques of production. Here, following criteria were used: pressure force, size of acoustic signal in load function as well as appearance of specimen. Key words: braiding, filament winding material characterization, multiaxial state of stress, composite tube AE