Life after extinction: palaeoenvironments of the earliest Triassic lower Katberg formation, including the origin of Lystrosaurus Bonebeds from the Karoo Basin, South Africa

Includes abstract.Includes bibliographical references.This study argues for the formation of bonebeds by aggregation of sub-adult Lystrosaurus during extended episodic periods of extreme climatic conditions, such as cold or drought, in the earliest Triassic Karoo Basin

Free vibration analysis of locally damaged aerospace tapered composite structures using component-wise models

This work presents the free vibration analysis of tapered aircraft structures made of composite and metallic materials, with reference to global and local damage. A refined one-dimensional model, developed in the framework of the Carrera Unified Formulation, has been used to provide a detailed description of structures. Multi-component aeronautical structures have been modeled adopting Lagrange polynomials to evaluate the displacement field over the cross-section. Each component has been described through the component-wise approach, with its own geometrical and mechanical characteristics. The effects of localized damage have been investigated, thanks to the accuracy of the layer-wise models adopted. The model has been assessed by comparing the results with classical FE models. The results show that the present approach provides an accurate solution for the free vibration analyses of complex structures and is able to predict the consequences of a global or local failure of a structural component. The computational efficiency and the accuracy of the model used in this work can be exploited to characterize the dynamic response of complex composite structures considering a large number of damage configurations

Analysis of tapered composite structures using a refined beam theory

This work presents some static analyses on reinforced thin-walled tapered structures made of composite material. These applications are performed through a refined one-dimensional model based on the Carrera Unified Formulation. This formulation uses polynomial expansions to describe the displacement field over the cross-section of the beam. In this way, a quasi three-dimensional solution can be obtained. In the present work the cross-sectional kinematic has been described using the Lagrange polynomials. The use of such models allows any component of the structure to be modelled separately and then the complex structure can be obtained thanks to the so-called component-wise approach. Different aeronautical structural components, gradually more complex, have been studied. The stress and displacement fields due to simple loads have been obtained. The results have been compared with those obtained by means of a commercial FEM tools using one-, two- and three-dimensional elements. The results obtained show how the present approach can deal with complex structures such as tapered aeronautical components. The use of refined beam models allows complex stress fields to be accurately evaluated that is composite materials can be investigated

Free vibration analysis of variable angle-tow composite wing structures

This paper investigates the possibility to improve the dynamic response of complex aeronautical structures using variable angle-tow composites. The study has been performed using an innovative numerical approach developed in the framework of the Carrera Unified Formulation able to study laminates with curvilinear fibres whose trajectories can be arbitrarily defined. Refined kinematic structural models have been used to deal with the complex behaviour of such structures. Several cases have been investigated in order to validate this approach and the results have been compared with those from classical modelling approaches. Simple beam models and complex wing structures, have been considered. The effects of different fibres-paths have also been studied and compared. The results confirm that an appropriate tow lay-up can be used to improve the performances of wing structures, i.e. innovative design solutions can be achieved