Evaluation of in-plane shear failure in composite laminate with high percentage of 90o plies

The first step in analysis composite joint is to have a correct and appropriate definition of properties of material used. The effect of fibre orientation and the interaction between them in the laminated composite play a key role in determining the laminate characteristics, the laminate mode of failure as well as the overall mode of joint failure. In order to study the failure of a new generation of composite laminate joints, sets of material properties are needed in three directions. This paper present the study of the in-plane (interlamina) shear properties and the behaviour of a specific Carbon Fibre Reinforced Plastic (CFRP) laminate with a particular balanced lay-up under compression load. This paper presents the continuation of a previous study by the author to study shear in a specific CFRP Ref [1

Non-destructive testing and assessment of dynamic incompatibility between third-party piping and drain valve systems: An industrial case study

This paper presents the outcome of an industrial case study that involved condition monitoring of piping system that showed signs of excess fatigue due to flow-induced vibration. Due to operational requirements, a novel non-destructive assessment stratagem was adopted using different vibration analysis techniques - such as experimental modal analysis and operating deflection shapes - and complemented by visual inspection. Modal analysis carried out near a drain valve showed a dynamic weakness problem (several high-frequency flow-induced vibration frequency peaks), hence condition-based monitoring was used. This could easily be linked to design problem associated with the dynamic incompatibility due to dissimilar stiffness between two third-party supplied pipe and valve systems. It was concluded that this is the main cause for these problem types especially when systems are supplied by third parties, but assembled locally, a major cause of dynamic incompatibility. It is the local assembler's responsibility to develop skills and expertise needed to sustain the operation of these plants. This paper shows the technique used as result of one such initiative. Since high amplitude, low-frequency displacement can cause low cycle fatigue, attention must be paid to ensure flow remains as steady state as possible. The ability to assess the level of design incompatibility and the level of modification required using non-destructive testing is vital if these systems are to work continuously. © 2014 Taylor & Francis

Optimum Design of Fibre Orientation in Composite Laminate Plates for Out-Plane Stresses

Previous studies have shown that composite fibre orientations can be optimised for specific load cases such as longitudinal or in-plane loading. However, the methodologies utilised in these studies cannot be used for general analysis of such problems. In this research, an extra term is added to the optimisation penalty function in order to consider the transverse shear effect. This modified penalty function leads to a new methodology whereby the thickness of laminated composite plate is minimized by optimising the fibre orientations for different load cases. Therefore, the effect of transverse shear forces is considered in this study. Simulated annealing (SA) is used to search for the optimal design. This optimisation algorithm has been shown to be reliable as it is not based on the starting point, and it can escape from the local optimum points. In this research, the Tsai-Wu failure and maximum stress criteria for composite laminate are chosen. By applying two failure criteria at the same time the results are more reliable. Experimentally generated results show a very good agreement with the numerical results, validating the simulated model used. Finally, to validate the methodology the numerical results are compared to the results of previous research with specific loading

Combined analytical/FEA-based coupled aero structure simulation of a wind turbine with bend–twist adaptive blades

The simulation of wind turbines with bend–twist adaptive blades is a coupled aero-structure (CAS) procedure. The blade twist due to elastic coupling is a required parameter for wind turbine performance evaluation and can be predicted through a finite element (FE) structural analyser. FEA-based codes are far too slow to be useful in the aerodynamic design/optimisation of a blade. This paper presents a combined analytical/FEA-based method for CAS simulation of wind turbines utilising bend–twist adaptive blades. This method of simulation employs the induced twist distribution and the flap bending at the hub of the blade predicted through a FEA-based CAS simulation at a reference wind turbine run condition to determine the wind turbine performance at other wind turbine run conditions. This reduces the computational time significantly and makes the aerodynamic design/optimisation of bend–twist adaptive blades practical. Comparison of the results of a case study which applies both combined analytical/FEA-based and FEA-based CAS simulation shows that when using the combined method the required computational time for generating a power curve reduces to less than 5%, while the relative difference between the predicted powers by two methods is only about 1%

Application of combined analytical/FEA coupled aero-structure simulation in design of wind turbine adaptive blades

This paper demonstrates the application of combined analytical/FEA coupled aero-structure simulation in design of bend-twist adaptive blades. A genetic algorithm based design tool, in which the power curve is predicted through a combined coupled aero-structure simulation, has been developed. A bend-twist adaptive blade has been designed to be used on the rotor of a constant speed stall regulated wind turbine. The bend-twist adaptive blade is assumed to be made out of anisotropic composite materials. The designed blade has the same aerofoil and chord distribution as the original blade used on the wind turbine, but with a different pre-twist distribution. The simulated results show a significant improvement in the average power of the studied stall regulated wind turbine when employing the designed adaptive blades

Simulation of Performance Enhancement of Bi-Lateral Lower-Limb Amputees Through Impulse Synchronisation with Self Selected Running Step Frequency

Current method of enhancing the performance of a bilateral amputee runners using energy return prosthesis is rarely linked to the system dynamics. In this paper a simple simulation is used to show that if a self selected running step frequency could be synchronized with dynamic elastic response of a mass spring system extra gain in height or faster take off velocity can be achieved which results is higher state of energy equilibrium that is more favourable to running activity. Current method often relies on physiological methodology, making the differentiation between the contributions from the biological and the prosthetic element of the below-knee amputee athlete difficult. In this paper a series of mass and composite foot system are modelled based on a combination of mass, spring and damper arrangement to study the effect of gravity, mass, stiffness, damping and inertia on the dynamics characteristics of prosthesis and how human can instinctively detect the natural elastic response of such system both to cyclic excitation and impulse through self selection of frequency or impulse.It will be demonstrated that if the natural characteristics of a system are identified and synchronised with the physiological gait behaviour of a runner, performance enhancement could occur that can be stored and controlled at will by the user. In the case of a bi-lateral amputee athlete with near symmetrical gaitit can result in steady state running which can be beneficial over longer distances. Keywords: Amputee, Prosthesis, Lower-Limb, Foot, Energ

Decoupled aerodynamic and structural design of wind turbine adaptive blades

The simulation of wind turbines with bend–twist adaptive blades is a coupled aero-structure (CAS) procedure. The blade twist due to elastic coupling is a required parameter for wind turbine performance evaluation and can be predicted through a finite element (FE) structural analyser. FEA-based codes are far too slow to be useful in the aerodynamic design/optimisation of a blade. This paper presents a combined analytical/FEA-based method for CAS simulation of wind turbines utilising bend–twist adaptive blades. This method of simulation employs the induced twist distribution and the flap bending at the hub of the blade predicted through a FEA-based CAS simulation at a reference wind turbine run condition to determine the wind turbine performance at other wind turbine run conditions. This reduces the computational time significantly and makes the aerodynamic design/optimisation of bend–twist adaptive blades practical. Comparison of the results of a case study which applies both combined analytical/FEA-based and FEA-based CAS simulation shows that when using the combined method the required computational time for generating a power curve reduces to less than 5%, while the relative difference between the predicted powers by two methods is only about 1%

Efficient meshing of a wind turbine blade using force adaptive mesh sizing functions

This paper describes mesh sizing functions for discretization of a wind turbine blade as a shell structure. Two different functions, one along the blade span and the other chord-wise, are presented. The effect of the magnitude of the aerodynamic force has been considered in a span-wise mesh sizing function to obtain a force-adaptive mesh generator, applicable when the blade needs to be analysed as a part of an aero-structure problem. The direction of the aerodynamic force has been considered in the chord-wise mesh sizing function to improve the mesh efficiency. Results show a large improvement in the rate of convergence when the direction of the external force contributes towards the chord-wise mesh size