Multistable fibre-reinforced composites with cutouts
Werner Hufenbach, Maik Gude, Lothar Kroll, Bernd Werdermann, Andrzej Czulak Technische Universität Dresden, Institut für Leichtbau und Kunststofftechnik (ILK), 01062 Dresden, Germany
Annals 3 No. 7, 2003 pages 238-242
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abstract During the manufacturing process and operating conditions of multilayered fibre-reinforced composites with variable fibre orientations, residual stresses build up due to the directional expansion of the unidirectionally reinforced single layers. Dependent on the laminate lay-up, these inhomogeneous residual stresses, which are primarily caused by thermal effects, moisture absorption and chemical shrinkage, can lead to large multistable out-of-plane deformations in the case of asymmetric laminates. For the calculation of the laminate deformations and the residual stresses especially around a notch, a dimensioning tool based on a modified stability analysis in combination with stress concentration model has been developed. A solution method has been developed for stress concentration problems of fibre-reinforced compounds based on the method of complex-valued stress function combined with conformal mappings. Using this method, stress and displacement fields of anisotropic multilayered plates with cut-out can be calculated. For finite boundary the solution is analytically continued from the inner boundary to the rest of the plate. The remaining unknowns are obtained semi-analytically using a combination of boundary collocation method and least squares method. As the computation examples demonstrate, this analytical approach is markedly superior to a finite element analysis. Key words: multistable composites, residual stresses, stress concentration