Research on the dynamic buckling characteristics of carbon fiber composite honeycomb panel under out-of-plane impact load Fan Ming Jun

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1 Advanced Materials Research Submitted: ISSN: , Vols , pp Accepted: doi: / Online: Trans Tech Publications, Switzerland Research on the dynamic buckling characteristics of carbon fiber composite honeycomb panel under out-of-plane impact load Fan Ming Jun Military representative office in the wuhan an institute shipyard, Wuhan, , P.R.China Keywords: honeycomb, composite, dynamic buckling, impact Abstract: This paper aims at studying the dynamic buckling characteristic of the fiber composite honeycomb under out-of-plane impact load. It was found that: with the increasing of the wall thickness, both the critical buckling load and the critical failure load of the composite honeycomb will decrease gradually. By increasing the wall aspect, the critical buckling load will decrease, while the critical failure load will increase. However, when the aspect reaches to 3.5,both the above two kinds of load are no longer sensitive to the variation of it. Introduction The honeycomb panel has been more and more commonly used in the aerospace field these years since it can reduce the weight of satellite and aircraft [1]. However, with the deep going application, corrosion problem caused by aluminum-carbon electrochemical reaction when bonding the traditional aluminum-made honeycomb with the carbon fiber composite panels has become more and more prominent. Honeycomb made of carbon fiber composite laminates not only can solve the problem but also can further decrease the weight of structures. Consider that the honeycomb is composed of numerous thin-wall laminates, and when subjected to out-of-plane load, especially for dynamic load, the cell walls may collapse [2]. So it is necessary to study the dynamic buckling characteristic of the carbon fiber composite honeycomb. This paper mainly studies the influence of impact time and honeycomb size on the critical buckling load and critical failure load. Finite element model and grid verification A honeycomb panel was manufactured by bonding the honeycomb core with two equal-thickness face sheets [3]. For a rectangular honeycomb panel subjected to out-of-plane load with four edges clamped, the thickness of the two face sheets determines the flexural capacities and the thickness of the honeycomb core determines the shear capacity. In this paper, the honeycomb panels to be investigated had both panels and honeycomb core made up of carbon fiber composite laminates. The panels had the same thickness as 2 mm, and they were composed of 4 equal-thickness composite laminates with an orthogonal stacking sequence. The honeycomb core had several thicknesses which varied from 5mm to 25mm and one thickness was 5mm apart from another one. The cell wall had a constant width as 5mm, while thicknesses varied from 0.08mm to 0.16mm and one was 0.04mm apart from another one. A schematic of honeycomb panel subjected to out-of-plane impact load is shown in Figure 1.The specimen was supposed to lay on the platform, and the upper face sheet was ready for the transcendent equal impact pressure in the normal direction. 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, (ID: , Pennsylvania State University, University Park, USA-10/05/16,13:56:24)

2 Advanced Materials Research Vols panel honeycomb panel Platform Fig. 1 Schematic of honeycomb panel subjected to out-of-plane impact load The infinite composite honeycomb was simplified before the finite element modeling, and it contained a total of seven honeycomb cells with special periodic boundary constraint as Figure 2 shows. Fig. 2 The simplified FEA model of the composite honeycomb Through the impact, the carbon fiber composite may fail owing to the excessive stress. In order to make the simulation more accurate and authentic, the finite element procedure had to consider the strength of the material. As the carbon fiber composite belongs to the brittle materials, the yield phase can be ignored. The mechanical properties of the carbon fiber composite material are listed in Table 1 [4]. Table 1 The mechanical properties of the carbon fiber composite material E 1 (MPa) E 2 (MPa) γ 12 G 12 (MPa) G 23 (MPa) ρ (kg/mm 3 ) E-12 S lt (MPa) S lc (MPa) S ls (MPa) S tt (MPa) S tc (MPa) S ts (MPa) In order to verify the accuracy of the simplified finite element model, honeycomb made of steel with wall width as 5mm, thickness as 0.25mm, and wall height 15mm under quasi-static compression was simulated. Figure 3 shows the comparison of the pressure-strain curves of the simulation and the experiment.

3 Pressure/Mpa 494 Advanced Materials and Technologies Experiment Caculated Strain/% Fig. 3 Comparison of the pressure-strain curves of the simulation and the experiment This paper tries to use the B-R [5] method to determine the critical dynamic buckling load of the composite honeycomb subjected to out-of-plane impact load, as it is relatively convenient and precise for the shell structure. For the dynamic buckling of the composite honeycomb discussed in this paper, in order to apply the B-R method and determine the initial buckling load, the incremental impact load peak is selected to be the independent variable, and the maximum average vertical displacement of the honeycomb s upper face sheet during the impact time is selected to be the dependent variable. Figure 4 gives the curve of the dimensionless maximum average vertical displacement of the honeycomb s upper face sheet varying with the dimensionless impact load peak. It exhibits that when the dimensionless load peak increase to about 1.68, the slope of the curve grows larger and larger. Referring to the B-R method, 1.68 is the dimensionless critical dynamic buckling load in this case. Fig. 4 Curve of maximum average vertical displacement of the honeycomb s upper face sheet varying with the impact load peak Discussion on parameters Six honeycomb panels with different sizes were investigated. Fig show the variation of the critical buckling load (left) and the critical failure load (right) with the different wall aspects and thicknesses under different impact time.

4 Advanced Materials Research Vols Fig. 5 Critical buckling load of the honeycomb Fig. 6 Critical failure load of the honeycomb under the impact time as 0.5 under the impact time as 0.5 Fig. 7 Critical buckling load of the honeycomb Fig. 8 Critical failure load of the honeycomb under the impact time as 1.0 under the impact time as 1.0 Fig. 9 Critical buckling load of the honeycomb Fig. 10 Critical failure load of the honeycomb under the impact time as 2.0 under the impact time as 2.0 Fig Variation of the critical buckling load (left) and critical failure load (right) with different wall aspects and thicknesses. It exhibits that, with the increasing of the wall aspect, the critical buckling load decreases quickly from the start and then stabilized gradually, while the critical failure load increases quickly from the very beginning and then stabilized gradually. When the aspect reaches to 3.5, both the above two kinds of load are no longer sensitive to the change of the aspect. On the other hand, with the increasing of the wall thickness, both the critical buckling load and the critical failure load decrease more or less.

5 496 Advanced Materials and Technologies Conclusion This paper focuses on forecasting the final status of the impacted composite honeycomb, around which, a series of simulations of the impact test has been done and analyzed. Finally the conclusions are that: 1. With the increasing of the wall thickness, both the critical buckling load and the critical failure load of the composite honeycomb decrease gradually. 2. By increasing the wall aspect, the critical buckling load will decrease, while the critical failure load will increase. However when the aspect reaches to 3.5, both the two kinds of load are no longer sensitive to the variation of it. References [1] Mijia Yang and Pizhong Qiao.Quasi-static Crushing Behavior of Aluminum Honeycomb Materials.Journal of Sandwich Structure and Material, :133. [2] Mete Onur Kaman,Murat Yauz Solmaz and Kadir Turan.Experiential and Numerical Analysis of Critical Buckling Load of Honeycomb Sandwich Panels,Journal of Composite Materials, : [3] G.S.Langdon,G.N.Nurick,M.Yazid Yahya and W.J.Cantwell.The Response of Honeycomb Core Sandwich Panels,with Aluminum and Composite Face Sheets,to Blast Loading,Journal of Sandwich Structures and Materials, :733. [4] Jin Yuan,Wang Yumin,Han Jingtao,Guo Shiju.Quasi-static Compression Energy-absorption Properties of Steel Honeycomb Structures, Material for Mechanical Engineering, :5. [5] Budiansky B. and Hutchinsion J,Dynamic buckling of imperfection -sensitive structures,proceeding of the Eleventh International Congress of Applied Mechanics,Springer-Verlag,Berlin,1964.

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