Download files
Abstract
The development of elastically-tailored self-adaptive structures through the use of anisotropic advanced composite materials continues to attract more interest and new applications. However, the process required to design a structure which exploits the elastic-couplings of an anisotropic material is complex. Considerably more understanding of advanced composite materials is required to successfully deliver a tailored elastic response than is required to design a typical laminate. The research of this thesis has thoroughly assessed the effectiveness of using first-order theories to approximate the deformation response of laminated bend-twist coupled cantilever beams/plates as a method for developing system understanding during preliminary design. The bend-twist coupling response of laminated cantilevered strips was measured to higher levels of accuracy than other examples in the literature with the aid of a 3-D laser scanner. The experimental results were compared with one-dimensional analytical models and finite element numerical simulations (both derived from first-order laminated plate stiffnesses) to assess the accuracy and effectiveness of the first-order approximations for developing an understanding of bend-twist coupled cantilever response. Through this research it was demonstrated that the understanding of a bend-twist coupled cantilever can be significantly enhanced with the use of simple and uncomplicated methods derived from the elementary laminated plate theories. The one-dimensional model was found to provide liberal (overestimated) deflection and twist approximations, the magnitude of which was dependent on planform aspect ratio and material properties. The main contributor to the inaccuracy of the one-dimensional models was attributed to the restraint of rotation at the finite width fixed-end boundary. However, specific insight has arisen from this research which shows that in spite of the systematic overestimation of deflection and twist, a first-order approximation provides considerable insight into the deformation response of bend-twist coupled cantilevers. In addition to deformation approximations, it was also found that there are certain aspects of first-order laminated plate models which are very effective at characterising the bend-twist coupling response of thin cantilevers. The locus of flexural-centres, the bend-twist coupling twist rate and a new parameter, the Cross-Sectional Centre of Twist, were all demonstrated to be accurately approximated by expressions derived from the one-dimensional model.