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Djojodihardjo H.,University Putra Malaysia | Djojodihardjo H.,Al - Azhar University of Indonesia
Proceedings of the International Astronautical Congress, IAC | Year: 2013

The development of high-strength, high-modulus fibers, has allowed the development of current projectile's impact et resistant and compliant laminates. At a sufficiently low velocity, below the critical velocity, initial stress in the laminates increase is insufficient to rupture the fibers; thus allowing transverse deflection and fiber extension time to propagate, resulting in the absorption of energy by the laminate Damage mechanisms are dependent on the projectile geometry and velocity, the properties of the matrix and fibers and the fiber-matrix adhesion. It should be noted that for ballistic applications, weak fiber-matrix adhesion is wanted. Related to spacecraft debris hazard, one has to quantify the risk and determining appropriate means to protect the spacecraft. An improved understanding of the debris environment, combined with the growing availability of analytic and experimental tools to quantify the threat to a spacecraft from debris and the development of techniques to protect against debris impacts, now makes it feasible for designers to assess the debris hazard and protect their spacecraft appropriately. With such perspectives, this work looks at a plate structure modeled as Mindlin plate subject to impact loading and carry out analysis and numerical simulation. The first objective of the work is to develop a computational algorithm to analyze flat plate as a generic structure subjected to impact loading for numerical simulation and parametric study. The second objective is to utilize the computational algorithm for direct numerical simulation. Effort is devoted to arrive at optimum configurations. Copyright © 2013 by the International Astronautical Federation. Source


Djojodihardjo H.,University Putra Malaysia | Djojodihardjo H.,Al - Azhar University of Indonesia
Proceedings of the International Astronautical Congress, IAC | Year: 2013

With the remarkable computing capability and the availability of sophisticated, user-friendly computer-aided analysis software, the analyst main challenge is to insure that the analysis includes all the relevant physical phenomena. However, simple fundamental principles are mandatory, in order not to lose insight on the interrelationships between relevant elements, and to device simple methods that are robust, and amenable to modifications to address various problem categories. Space borne structure must fulfill various requirements, such as to resist the loads induced by the launch environment, and meet all the functhnal performances required on orbit such as dimensional stability and structural integrity. Space borne structure must also interface with some other subsystems. Noise and Vibration should also be taken as critical consideration in the design of aerospace vehicles for fatigue of components arising from interior structural and acoustic pressure fluctuations due to external structural or acoustic loading. Lightweight structures for high-technology applications increasingly have to fulfill not only high demands on stiffness and strength but also on high damping and low sound radiatbn due to the rising comfort requirements. Here, composites offer a very high vibro-acoustic lightweight potential. The great number of design variables allows to synergetically fulfill high stiffness and acoustic standards. Hence the objective of the present paper is to describe the application of BE-FE Fluid Structure interaction on a structure subject to acoustic load and to elaborate FE formulation of the computational scheme for unified approach on acoustic-aeroelastic interaction as developed earlier. The modal representation of a mechanical structure can be determined analytically if a lumped mass-spring system is concerned. In the general case of a continuous structure, a numerical approximation by means of a Finite Element Model (FEM) is made, discretizing the structure in a finite number of physical coordinates. The present work then proceeds with the dynamic response analysis of typical and generic space shell structure subject to acoustic loading. The numerical treatment applicability is investigated and validated through application to generic cases. The analysis carried out in the work is intended to serve as a baseline in the analysis of acoustic structure interaction for lightweight composite structures by analyzing the structural-dynamic response and sound radiatbn of composite shells, utilizing the authors developed numerical vibro-acoustic simulation models. The work carried out thus far is focused on the formulation of the basic problem of acoustic excitation and vibratbn of elastic structure in a coupled fluid-elastic-structure interaction. Copyright © 2013 by the International Astronautical Federation. Source


Suryana R.,Al - Azhar University of Indonesia
INTELEC, International Telecommunications Energy Conference (Proceedings) | Year: 2011

This paper presents the frequency control strategy of standalone wind turbine with a doubly fed induction generator supported by a supercapacitor as an energy storage. The electrical power frequency will be oscillation when the amount of active power produced by wind turbine is not equal to the amount of active power required by consumer. The wind power generation is varying because wind existence is not constant. The supercapacitor will support system to maintain frequency stability. © 2011 IEEE. Source


Djojodihardjo H.,University Putra Malaysia | Mahmud A.S.,Al - Azhar University of Indonesia
Applied Mechanics and Materials | Year: 2014

A set of Mindlin plates bonded together is subjected to loading by impact, which is considered to represent a generic engineering structure and is analyzed through numerical simulation. The objective is to identify optimum configuration in terms of loading, structural dimensions, material properties and composite layup associated with micrometeorites impacts on spacecraft that will not penetrate into its structure. Following the algorithm developed for the problem, the work comprises an in-depth analysis of a generic flat plate structure subjected to impact and numerical simulation. The analyses are based on dynamic response with emphasis on the elastic region. The direct numerical simulation is carried out in parallel for the analysis, synthesis, parametric study and optimization. As simulation case study, the panel structure response to impact loading by a spherical rigid body at certain velocity perpendicular to the panel plate itself and numerical simulation is carried out as appropriate. Simulation results are validated through comparison with analytical work. The entire scheme carried out in this work is a novel comprehensive approach for the structural design of non-penetrated impact on metallic composites. The results show that the use of composites, in particular the bi-metallic composite, is instrumental in tailoring the plate materials to achieve non-penetrating impact. © (2014) Trans Tech Publications, Switzerland. Source


Djojodihardjo H.,University Putra Malaysia | Djojodihardjo H.,Al - Azhar University of Indonesia | Mahmud A.S.,University Putra Malaysia
Journal of Aerospace Engineering | Year: 2016

A computational modeling and simulation study is carried out to gain insight and formulate strategy for the design and tailoring of panel-like space structure that can withstand space debris impact without penetration. To represent a generic engineering structure, the impacted panel structure is modeled as a set of bonded plates. The analysis is based on fundamental principles, which are elaborated and numerically simulated. The objective is to identify optimum configuration in terms of loading, structural dimensions, material properties, and composite layup. The analyses are based on dynamic response with emphasis on the elastic region. The direct numerical simulation is carried out in parallel for the analysis, synthesis, parametric study, and optimization. Simulation results of impact loading by a spherical rigid body at certain velocity perpendicular to the panel show how fiber-metal laminates can be structurally tailored to achieve a nonpenetrating impact. © 2015 American Society of Civil Engineers. Source

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