Elements Of X Ray Diffraction

African vultures optimization algorithm: A new nature-inspired metaheuristic algorithm for global optimization problems

INTRODUCTION TO COMPOSITE MATERIALS Chapter Objectives Introduction Classi?cation Recycling Fiber-Reinforced Composites Mechanics Terminology Summary Key Terms Exercise Set References MACROMECHANICAL ANALYSIS OF A LAMINA Chapter Objectives Introduction Review of De?nitions Hooke's Law for Different Types of Materials Hooke's Law for a Two-Dimensional Unidirectional Lamina Hooke's Law for a Two-Dimensional Angle Lamina Engineering Constants of an Angle Lamina Invariant Form of Stiffness and Compliance Matrices for an Angle Lamina Strength Failure Theories of an Angle Lamina Hygrothermal Stresses and Strains in a Lamina Summary Key Terms Exercise Set References APPENDIX A: MATRIX ALGEBRA Key Terms APPENDIX B: TRANSFORMATION OF STRESSES AND STRAINS Transformation of Stress Transformation of Strains Key Terms MICROMECHANICAL ANALYSIS OF A LAMINA Chapter Objectives Introduction Volume and Mass Fractions, Density, and Void Content Evaluation of the Four Elastic Moduli Ultimate Strengths of a Unidirectional Lamina Coefficients of Thermal Expansion Coefficients of Moisture Expansion Summary Key Terms Exercise Set References MACROMECHANICAL ANALYSIS OF LAMINATES Chapter Objectives Introduction Laminate Code Stress-Strain Relations for a Laminate In-Plane and Flexural Modulus of a Laminate Hygrothermal Effects in a Laminate Summary Key Terms Exercise Set References FAILURE, ANALYSIS, AND DESIGN OF LAMINATES Chapter Objectives Introduction Special Cases of Laminates Failure Criterion for a Laminate Design of a Laminated Composite Other Mechanical Design Issues Summary Key Terms Exercise Set References BENDING OF BEAMS Chapter Objectives Introduction Symmetric Beams Nonsymmetric Beams Summary Key Terms Exercise Set References INDEX

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Mechanics of composite materials

Sapiens: A brief history of humankind

Recently published research indicates that natural fibre based polymer composites have limited applications in advanced structural systems due to their low impact performance. However, natural fibres have great potential for reducing the product weight, lowering material cost, and renewability. Hybrid composites made from a combination of natural/synthetic fibres, natural/natural fibres, or synthetic/synthetic fibres are also receiving attention from both researchers and the industry for structural applications owing to the tailored mechanical and impact properties of these materials. The hybridisation process is one of the paramount and more efficient ways to strengthen and improve the performance of composite materials. This review paper examines the impact properties of hybrid composites manufactured with the aim of improving their structural characteristics, and in particular, is focused on the impact resistance and penetration behaviour of hybrid composites reinforced with natural and synthetic fibres as well as their suitability for modern structural applications.

Impact behaviour of hybrid composites for structural applications: a review

Several studies have been carried out over recent years with the aim of obtaining ecofriendly, biodegradable, low cost, lightweight natural fiber reinforced polymer composites. In this article, two types of natural fibers, basalt and flax, together with their hybridization, have been used to reinforce a green vinyl ester matrix in a wet hand lay-up lamination. The hybrid composite, with flax fiber reinforcement (FFR) in the central zone and basalt fiber reinforcement (BFR) in the outer layers, was intended for construction of boats and yachts. The influence of BFR and FFR on the impact properties of dry and salt-water conditioned composite samples has been investigated. In particular, a comprehensive scanning electron microscope (SEM) analysis of the damaged surface and cross section has been undertaken in order to investigate the mechanisms of energy absorption. The results show significant impact behavior improvements for hybrid composites compared to single composites, especially in the case of conditioned samples.

Influence of moisture absorption on the impact properties of flax, basalt and hybrid flax/basalt fiber reinforced green composites

The present experimental investigation is aimed at performing an analysis of mechanical and impact properties of flax and basalt fibres and their hybrids using a vinylester resin to produce reinforced thermosetting composites. Laminates were fabricated by hand lay-up and resin infusion. Cure processes were accelerated and controlled by applying heat and pressure in autoclave. Tensile, flexural and falling weight impact tests were carried out, the latter with energies of up to 40 J. The results indicated that hybrid laminates did not mostly offer properties to the level predicted by an application of the rule-of-mixtures, especially as regards flexural performance. On the other side, advantages provided concerned in particular reducing the brittleness of basalt offering some evidence of plastic behaviour, especially related to the fact of flax fibre reinforced laminated providing a quite long period at quasi constant load during impact tests, therefore resulting in delayed failure, while extensive damage is produced. The results tend to challenge the idea that basalt/flax fibre hybrid laminates would offer a good performance only with the presence of basalt fibres in the outer layers and would suggest the possible adoption in future of more complex stacking sequences, involving intercalation of flax and basalt layers.

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Mechanical and impact characterisation of flax and basalt fibre vinylester composites and their hybrids

Modelling and simulating complex systems, such as forestry equipment, are often the only way for their full analysis and design. This problem may lead to a stiff set of equations that are followed by numerical problems. In this paper two alternative approaches are investigated. The first one refers to the use of a variable step of integration by continuous models adjusted to the fastest processes. The second one refers to the approximation of fast transitions by ideal instantaneous mode-transitions and hybrid models. These two approaches are analysed in the framework of bond graph. The classical bond graph is adopted for description of the continuous models, and the switched bond graph is preferred for description of the hybrid models. The model of check valve is used as a working example for illustration of results. Matlab/Simulink tools are used for modelling and simulation.

Simulation of hydraulic check valve for forestry equipment

Using a total quality strategy in a new practical approach for improving the product reliability in automotive industry

Concrete structures in military areas are subject to projectile impact both as a result of direct fire and in the form of splinters from explosives. These structures may be damaged, resulting in partial loss of integrity, but must leave the objects or individuals within them unharmed to the largest extent possible. The degree of damage depends on a variety of factors relating to the projectile, including its mass, geometry, impact velocity, trajectory and material properties. A number of controllable factors also relate to the characteristics of the concrete structure itself and the reinforcing material used to produce barriers. In order to analyse the structural response and optimize design parameters, various dynamics simulations have been performed in this work relating to projectile impact on concrete structures. To correctly model the impact, both non-linear material response and progressive finite element erosion have been taken into account. The numerical results have been discussed and compared with experimental results for three different impact scenarios, with good alignment achieved in terms of both penetration depth and crater size. This correspondence also demonstrated the pertinence of a specific material model, the Riedel-Hiermaier-Thoma (RHT) model within the LS Dyna FEM software package, in guiding and interpreting physical experiments in the case of impulsive projectile loading and penetration of concrete. The alignment between experiments and simulations also confirmed the robustness of the material model, specifically selected for this particular application.

Ana Pavlovic

Papers

Influence of moisture absorption on the impact properties of flax, basalt and hybrid flax/basalt fiber reinforced green composites

Mechanical and impact characterisation of flax and basalt fibre vinylester composites and their hybrids

Simulation of hydraulic check valve for forestry equipment

Using a total quality strategy in a new practical approach for improving the product reliability in automotive industry

Comparative numerical and experimental study of projectile impact on reinforced concrete