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|| Fleischer, J.; Koch, S. & Ruhland, P. (2016), Rotational Molding of Fiber Reinforced Plastics with Elastic Composite Core. Resource Efficiency for Global Competitiveness, Hrsg. Dimitrov, D. & Oosthuizen, T., S. 181-186.
The rotational molding with an elastic composite core is an interesting process for the manufacturing of fiber reinforced plastics (FRP) with polygon cross-section. The polygon shape can be used for an in-mould-assembly of FRP and metal structures. On this way a load transmission with combined form-fit and adhesive bonding can be realized. Those hybrid parts are a suitable lightweight solution for shafts, pipes and profiles.
The processing via rotational molding with composite core can be carried out as follows: First dry continuous fiber structures and the elastic composite core are assembled and then laid in a closed mold. Subsequently, liquid thermosetting resin is cast and the mold is rotated at high speed. During rotation the composite cores expands and pushes the matrix into the areas that normally, without the composite core, would not be impregnated. The rotation is continued until the fiber structure is fully impregnated and the polymer is cured.
Within this paper, the manufacturing of polygon profiles with an elastic composite core is described. An analytic approach is introduced, which enables an ideal design and material choice of the elastic composite core and the achievement of high fiber volume fractions for fiber reinforced plastic hollow structures. Furthermore the manufacturing of elastic cores are depicted.
| [ 2 ]
|| Nieschlag, J.; Ruhland, P.; Daubner, S.; Koch, S. & Fleischer, J. (2018), Finite element optimisation for rotational moulding with a core to manufacture intrinsic hybrid FRP metal pipes, Production Engineering, Band 12, Nr. 2, S. 239-247. https://doi.org/10.1007/s11740-017-0788-6
Lightweight construction is gaining in importance due to increasing demands for energy efficiency. In drive technology, lightweight shafts can for example be produced in a centrifugal process in which dry, hollow fibre preforms are impregnated with polymer resin and cured under rotation. Furthermore, hybrid FRP-metal lightweight shafts can be produced by intrinsically incorporating additional metal load-introducing elements into the process. Due to the nature of the process, the transition between the materials may be conducted in a form-fitting way. So-called centrifugal cores are used for being able to achieve a higher fibre-volume content or produce polygonal profiles with a form fit. The cores made of a silicone-lead compound expand due to the rotational forces. The resulting pressure leads to a good impregnation of the corner areas. Compared to cylindrical centrifugal cores, polygonal ones have a more complex geometry. Designing with FEM is consequently more appropriate. Therefore, this paper shall portray finite element modelling of a polygonal centrifugal core. The challenge of this endeavour constitutes in developing a centrifugal core, which expansion executes a constant impregnation pressure via the profile onto the impregnated fibre layer. For this purpose, the centrifugal core is modelled as an elastic body in ABAQUS. Subsequently, the centrifugal core’s optimum geometry is derived with an optimisation approach. In conclusion, the calculated centrifugal cores are produced in order to be able to manufacture hybrid shafts.
| [ 3 ]
|| Coutandin, S.; Brandt, D.; Heinemann, P.; Ruhland, P. & Fleischer, J. (2018), Influence of punch sequence and prediction of wrinkling in textile forming with a multi-punch tool, Production Engineering, S. 1-10. https://doi.org/10.1007/s11740-018-0845-9 [13.08.18].
Liquid composite moulding (LCM) processes show a high potential in automated, large scale production of continuous fibre-reinforced plastics (FRP). One of the most challenging steps is the forming of the two-dimensional textile material into a complex, three-dimensional fibre structure. In this paper, a multi-punch forming process is presented. The upper mould of a generic part geometry is divided into 15 independently controllable punches. Depending on the different punch sequences, draping effects as well as defects related to wrinkling and shearing of the textile material are investigated. It has been shown that the sequence of the punches has a significant influence on the final preform quality. To predict the resulting regions of wrinkling and shearing, a finite-element based simulation model is set up. Forming tests and simulations with different punch-sequences are then performed and evaluated for validation purposes. To make a statement about the global preform quality, different objective functions regarding wrinkling are presented and analysed.