Modal Properties of Hybrid Carbon/Kevlar Composite Thin Plate and Hollow Wing Model H. Haidzir a , D. L. Majid b , A. S. M. Rafie c and M. Y. Harmin d Department of Aerospace Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia a haidziran@yahoo.com, b dlaila@eng.upm.edu.my, c shakrine@eng.upm.edu.my, d my@eng.upm.edu.my Keywords: Hybrid Kevlar composite, hollow wing, modal parameters, modal analysis. Abstract. In any flutter prediction analysis, modal testing is necessary because flutter, a resonant like vibration occurs at a flutter frequency and adopts a mode shape akin to its structural natural modes. Modal testing can be performed computationally with knowledge of the mechanical properties of the structure. In the present work, computational modal analysis is first performed on a cantilevered hybrid composite thin plate and validated experimentally. Then, the computational procedure is demonstrated on a composite hollow wing model of same material. The concept of hollow wing is explored due to the superior mechanical properties of carbon/kevlar composite plate. It is observed that the natural frequencies of the hollow wing model are higher than thin plate due to stiffer configuration. A breathing mode was also observed at mode 4 for the hollow wing. Introduction Each aerospace vehicle should be clear from flutter within their flight envelope. This is one criteria that should be fulfilled by all flight vehicles. Traditionally, there are two ways to test flutter which are flight testing and wind tunnel testing. Both techniques can cost money and occur late at design stage. Therefore, engineers rely on the computational method which benefits on the cost and time as well as flutter can be determined at the early design stage [1]. Computational aeroelasticity required dynamic properties (modal parameters) of the structure to be analyzed a process which known as modal analysis. There are few traditional methods to determine the modal parameters such as ground vibration testing, impact hammer testing, shakers and pickups and so on [2]. To reduce time and errors computational modal analysis is popular among the other methods. This had been a trend for engineers and researchers to perform analysis because of the advantages offers by this technique [3,4]. Through the paper, work done on determination of modal parameters of hollow composite wing by employing numerical (computational) techniques is presented. MSC.PATRAN and MD. NASTRAN will be used as the solver, pre and post-processing.The work is applied first on composite thin plate for the purpose of technique validation. An experimental work had been done on composite flat plate to verify the results with computational method. Then the same technique will be applied on hollow composite wing. For experimental work, impact hammer testing will be applied on thin plate by using a laser vibrometer and an accelerometer to measure the response. This experimental technique was developed by Saffry, Majid and Haidzir [5]. Methodology Experimental. The composite flat plate was fabricated with three layers of woven carbon/Kevlar cloth with epoxy resin by using wet hand layup and vacuum bagging technique. The cloth was aligned in the same direction for all three layers. Mechanical properties of the structure are required when performing computational analysis. To determine the properties, tensile test was performed on the composite plate. Results of this test, as Table 1, were derived from ASTM D3039 [6]. The thin flat strips (specimen) for this test were fabricated with eight layers of woven hybrid carbon/Kevlar with the same techniques to fabricate thin plate. Applied Mechanics and Materials Vols. 446-447 (2014) pp 597-601 Online: 2013-11-08 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.446-447.597 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 194.27.49.167, Atatürk Üniversitesi, Erzurum, Turkey-25/10/15,20:44:30)