Experimental Investigation and Finite Element Analysis of Composite Conical Structures Subjected to Slip Loading
Aljibori, Hakim S. Sultan (2006) Experimental Investigation and Finite Element Analysis of Composite Conical Structures Subjected to Slip Loading. PhD thesis, Universiti Putra Malaysia.
One of the main objectives of aircraft and automotive manufacturers is related to improvement of the crash behaviour of lightweight structures. The absorbed energy is an important parameter for the development of the vehicle passive security concept. An energy absorption device is a system that converts totally or partially kinetic energy into another form of energy during collision, which is required of an ideal energy absorbing material, is to have the capability of dissipating as much energy as possible per unit weight/ volume. The increasing demand of composite structures in wide range of engineering applications, structures made from composite materials offers important characteristics such as weight reduction, design flexibility and safety improvement. These composite structures provide higher or equivalent crash resistance as compared to their metallic counterparts and therefore find for its using in crashworthiness applications. Polymer composite materials have been introduced in the automotive industry primarily to reduce the overall weight of the vehicle, which results in energy economy and for better fuel cost. However, the current trend in producing lighter structures puts greater demands on the design of more efficient energy dissipating systems. The present study is essentially motivated by the increasing use of composite conical structures in crashworthiness applications. This study focuses on experimental and finite element investigation of glass fibre/epoxy and carbon fibre/epoxy composite conical shell were carried-out during the slipping of solid cone or composite cone into composite conical shell under radial and axial loading. This study has been divided into two main parts: Quasi-static methods and explicit integration methods (dynamic). These parts have been divided also into two sections concerning the problem solution. The first section is the finite element solution, which deals with composite conical shell in order to quantify the study and the second section is an experimental work. These methods used to improve the specific energy absorbed by crushed composite collapsible conical energy absorber devices were undertaken. LUSAS finite element analysis software was used for quasi-static method and ANSYS/LS-DYNA finite element software for dynamic explicit integration method were used to develop the models. Shell elements have been selected for the composite cones with the same wall thickness. Glass and carbon fibres have been used for the fabrication process of the specimens. The cone semi angles used were 4, 8, 12, 16 and 20 degrees. The cone dimensions were constant for all models as 100 mm height and 76.2 mm of bottom diameter. Load-displacement curve and deformation histories obtained from quasi-static work include the experimental and finite element results. These results obtained to calculate specific energy absorption and volumetric energy absorption. As well as others parameters, such as crush force efficiency, initial failure indicator, strain efficiency and failure modes. The results show that the cone angle, loading condition, fibre orientation and stacking sequence angle affects the load carrying capacity and energy absorption capacity of conical shell. On the other hand, the results obtained from finite element analysis for slipping crushed woven roving glass/epoxy composite conical shell by using the explicit integration methods was presented and discussed. The effects of geometrical on energy absorption characteristics and failure modes are investigated as well as the behaviour of structure subjected to dynamic loading. The kinetic energy and energy absorption capability was calculated and failure modes for non-linear dynamic analysis of structures in three dimension was identified. The load-time history curve and deformation history obtained from dynamic work also presented and discussed. The results show that the cone angle, fibre type and loading condition affect the load carrying capacity and energy absorption capacity of composite conical shell.
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