Javid Bayandor

A Finite Element Methodology for Analysing Degradation and Collapse in Postbuckling Composite Aerospace Structures

A methodology for analysing the degradation and collapse in postbuckling composite structures is proposed. One aspect of the methodology predicts the initiation of interlaminar damage using a strength criterion applied with a global-local analysis technique. A separate approach represents the growth of a pre-existing interlaminar damage region with user-defined multi-point constraints that are controlled based on the Virtual Crack Closure Technique. Another aspect of the approach is a degradation model for in-plane ply damage mechanisms of fiber fracture, matrix cracking, and fiber-matrix shear. The complete analysis methodology was compared to experimental results for two fuselage-representative composite panels tested to collapse. For both panels, the behavior and structural collapse were accurately captured, and the analysis methodology provided detailed information on the development and interaction of the various damage mechanisms.

A Review of Explicit Finite Element Software for Composite Impact Analysis

As explicit finite element (FE) codes improve and advanced material models become available, such tools will find more widespread application within the aerospace industry, as ‘what-if ’ simulations become more manageable with increasing computing power and greater modeling realism. This paper describes the investigation of three commercial explicit FE analysis packages, LS-Dyna, MSC.Dytran, and Pam-Shock, to determine their capabilities in predicting barely visible impact damage (BVID) in composite structures. The investigation is conducted by first determining the suitability of the codes in constructing an FE model of a stiffened panel, solving for BVID and retrieving results. The results are in turn compared to experimental data in order to gauge the suitability of the codes for composite design and analysis. Comparisons of the FE simulations to experimental data include damage development and degradation, as well as the time-history responses. The Chang-Chang failure theory with brittle degradation was used for both LS-Dyna and MSC.Dytran, while the biphase model was used for Pam-Shock. Results indicated that the general shape of the force-time curves as well as the peak forces were predicted reasonably well. However, all simulations predicted a trough that was much less significant than the test results, as well as a shorter impact duration.

Structural Design and Analysis of a BWB Military Cargo Transport Fuselage

As a response to growing needs of airlifting capability, an ultra heavy lifting Blended Wing Body military cargo transport is proposed. The BWB configurations holds a major technical challenge in its center body structure resisting both cabin pressurization and wing bending loads. A Columned Multi Bubble Fuselage (CMBF) is introduced and analyzed for the wide and continuous cabin area. It replaces inter-cabin walls of the existing configuration with a series of columns to prevent the mission interruptions. In the initial development analysis, it was found that the CMBF has a significant weight advantages. The paper presents the preliminary structural design and its analysis results.

Explicit Finite Element Modelling of Impact Events on Composite Aerospace Structures

Advanced fibre composite materials are now widely used in aerospace structures due to their superior performance characteristics such as high specific strength and stiffness. However, their susceptibility to non–visible or barely–visible impact damage is a significant constraint in achieving optimum structural performance. Recent developments in explicit finite element codes such as MSC.Dytran, LSDyna, Pam–Shock and Radioss indicate that there is now considerable potential for the accurate prediction of transient dynamic behaviour and onset of critical impact damage in composite structures. A series of test cases has been developed to investigate the critical parameters associated with the modelling of composite stiffened panels used in large civil transport aircraft components.

Advanced Zero Head Propulsion in Review

This paper reviews the recently introduced concept of unsteady zero-head propulsion (HYPS© ) and its particular attributes offering to revolutionize the conventional turbomachinery and fluid power technologies. The paper continues by underlining some of the fundamentals of the advanced concept that enable the system, in a unique way, to highly efficiently exploit the energy of turbulent and chaotic fluid flows. Extensive simulations and trial runs have highlighted the potential of the system in dealing with shortcomings of the traditional systems when encountered by random and multi-directional upstream flow conditions.Copyright

An investigation into an advanced composite finite element explicit biphase model: Part II - Damage parameters

The elastic and damage parameters of the ‘‘biphase’’ composite material and degradation model contained in the explicit finite element code, Pam-Shock, have been investigated in Parts I and II, respectively. The biphase analysis is a relatively new methodology aiming at accurately predicting the complex damage responses of composite structures to dynamic loading conditions. The intricacy of the damage mechanism dealt with hence calls for a broad range of elastic and damage parameters to be defined within the analysis before a solution corresponding to real case scenarios can be achieved. This investigation focuses on the unknown effects of such parameters and has been successful in identifying the significance and sensitivities that the variation of the parameters impose on the predicted outputs. It was established that the variation of some of the parameters, such as Poisson’s ratio, can cause a considerable deviation from the reference run, thus making it imperative to concentrate on deriving accurate empirical values to be used against such material properties within the analysis. A brief tabulated summary demonstrates the strengths and limitations of the model in predicting the response of advanced composite structures to impact events.

Advanced Unsteady Flow Control (Keynote Paper)

A general description, underlining some of the defining principles behind the revolutionary advanced unsteady propulsive system, is provided. The developed system is a large amplitude unsteady propulsion that leaves free trailing vorticity of magnitude O (e0 ) per unit of time down-stream of the flow. Having multiple degrees of freedom (sixteen for the scaled-down prototype) the system has been designed to efficiently operate in transitional and unsteady flows through sensing and capturing the energy of flow perturbations and turbulence in addition to that of the free-stream. Numerical studies, backed by experimental data, have demonstrated the high efficiency gain of the system in comparison to the conventional turbomachinery.Copyright

The Next Generation Feedback Controlled Propulsive System

A short synopsis pertaining to the concept, analysis and development of the new advanced zero head HYdro-Propulsive System (HYPS) has been drawn. Within this system, of particular importance are the implemented revolutionary feedback control systems. These systems provide the HYPS with a unique ability to efficiently receive and capture the kinetic energy embedded in multi-directional, random and turbulent fluid flow motions. The system is equipped with specially designed bladings (propulsors) that are attached through the feedback controllers to the extending radial arms, allowing the blades to adjust their orientations according to the oncoming flow. It has been demonstrated, through implicit analysis and extensive tests, that this system can effectively maximise the favourable aero-hydrodynamic forces on its impellers and, in turn, achieve a much higher energy conversion rate compare to those of the conventional devices.Copyright