Analysis of Composite Structure Using HM12.0/Radioss

Transcription

1 Analysis of Composite Structure Using HM12.0/Radioss Anil M.Sutar Design Engineer Citec Engineering India Pvt. Ltd. Yerwada, Pune Abbreviations: FE- Finite Element, GRP-Glass Reinforced Polymer. Keywords: Composite, Laminate, Composite Stresses, Failure Index Sushil More Lead Engineer Citec Engineering India Pvt. Ltd. Yerwada, Pune Abstract In recent years, usages of composite materials have progressed in automobile, aerospace industries and it is one of the alternatives for metal materials. This trend is because of their high strength to weight ratio and also it is possible to manufacture components as per required mechanical properties. Linear static and dynamic behaviors of thin laminate composite structures are analyzed in this study using the Finite Element Method. The main objective of this paper is to use Altair capabilities to analyses structure made with composite material. In this study HyperMesh 12.0 is used for pre-processing and Radioss as a solver. Different load cases with given boundary conditions & loadings are used. Current analysis is concluded by calculating displacement, composite stresses and Failure index for the structure. Altair HyperWorks Capabilities have been proved to simulate composite structures with defined orthotropic material properties (HyperMesh), problem solutions (Radioss) and effective result interpretation (HyperView). Introduction Composite materials consist of fibers of high strength and modulus embedded in or bonded to a matrix with distinct interfaces between them. In this form, both fibers and matrix retain their physical and chemical identities [1]. In recent years, usages of composite materials have progressed in automobile, aerospace industries and it is one of the alternatives for metal materials. This trend is because of their high strength to weight ratio and also it is possible to manufacture engineering components as per required mechanical properties & any complex shape. Composite structure starts with the incorporation of a large number of fibers into a thin layer of matrix to form a lamina (ply). Fibers in lamina may be arranged in a unidirectional, in a bidirectional orientation or in a multidirectional orientation. The thickness required to support a given load or to maintain a given deflection in a fiber-reinforced composite structure is obtained by stacking several laminas in a specified sequence is called as laminate [1]. Composite material is orthotropic material because properties in x,y and z direction is depends on fiber orientation e.g. For a lamina containing unidirectional fibers, has the highest strength and modulus in the longitudinal direction of the fibers & its strength and modulus are very low in the transverse direction. In the present study composite structure is analyzed using finite element method. The main objective is to check linear static and dynamic behavior of laminated composite structure using Altair CAE tools.this paper describe FE process to analyze composite structure i.e. FE model creation, define output request and results interpretation.hypermesh12.0 is used for pre-processing, FE model is solved in Radioss and analysis results are post processed in Hyperview. Different load and boundary conditions are used to calculate displacement, composite ply stresses and failure index. Commercial and industrial application areas of composites are aircraft, space, automotive, sporting items, marine, and infrastructure. In aerospace industry, wings spoiler, Wing skins & substructures and forward fuselage etc. are made with Composites. In automotive industry, body components, chassis components, engine components and exterior body parts like hood, door panels are made with fiber reinforced composites [1]. 1

2 FE Process for Composite Material General steps in finite element analysis are shown in Fig.1 Figure 1: Finite Element Process Composite is a laminated structure with orthotropic material properties so we need to define appropriate property and material cards. Also output definition of analysis and post processing techniques are different than the general procedure. Composite Structure and Material Properties Composite structure used in this study as shown in Fig.2 is made with GRP laminates and each GRP laminates will have different layer structure. Sample layer structure of one GRP laminates is shown in table.1 Figure 2: Composite Structure Table 1: Layer Structure of GRP Laminate SR. No. Fiber Orientation Material Thickness /90 0 X1 5X 2 +/ Y1 11X 3 +/ Y1 11X /90 0 X1 5X Where, x is multiplying factor 2

3 As GRP laminate is made with X1 and Y1 material, the properties for this material are shown in following table 2. Table 2: Material Properties Material E1 (GPa) E2 (GPa) G12 (GPa) Density Kg/m 3 Xt, Xc Yt, Yc S X Y Where E1 and E2 are modulus of elasticity in longitudinal and lateral direction respectively, G12 is In-plane shear modulus, Xt, Xc & Yt, Yc are allowable stresses in longitudinal and lateral direction respectively and S allowable In-plane shear. Finite Element Analysis Hypermesh 12.0 is used for discretization of composite structure. 2D mesh is generated on mid-surface of geometry with mixed mesh type (Quad4 and Tria3 elements). Appropriate 1-D elements are used for connection (i.e.rbe2, CBEAM and CROD elements). Following Fig.3 is mesh model of composite structure. Figure 3: FE Model Composite Structure PCOMPP property is assigned to mesh model, plies are then created for respective elements as per layer structure of shell with appropriate material, thickness and fiber orientation. Orthotropic material properties are defined in MAT8 card. Laminates are created as per sequence of plies. Outputs required from analysis are composite stress, composite Strain and displacement etc. There are different theories of failure available for composite material but we have used Hills failure theories in this study. Layered structure of one of the GRP laminate is shown in following fig.4 Figure 4: Layered Structure of Laminates Two load cases are considered in this study, i.e. 2g vertical and modal to check static and dynamic behavior of composite structure. 3

4 Analysis Results and Discussion Dynamic behaviour is analysed through modal analysis.modes and mode shapes for modal analysis are shown in Fig.5. Figure 5: Mode and Mode Shapes Linear static analysis is carried out by applying 2g vertical load on structure. Displacement, composite ply stresses and failure index are evaluated for this load case. Displacement plot, maximum composite stress and failure index are shown in Fig.6, Fig.7 and Fig.8 respectively. 4

5 Figure 6: Displacement Plot Figure 7: Composite Stresses (Maximum & on Ply 30) Figure 8: Failure Index 5

6 Result summary is shown in table 3. Table 3 : Result Summary Frequencies (Hz) Displacement (mm) Composite Stress Mode 1: 5.89 Mode 2: Mode 3: Mode 4: Mode 5: Mode 6: Max = On Ply 30 = Failure Index 0.22 To facilitate prediction of potential failure of the laminate, failure indices are calculated for plies and bonding material, value of a failure index lower than 1.0 indicates that the stress/strain is within the allowable limits As failure index for considered composite structure is 0.22 which is less than 1.0 means stresses in all laminae are within failure envelope. Benefits Summary Process is developed to simulate composite structure with different layers of plies using Altair HyperMesh. Time is reduced to decide different combination of plies to get required strength as HyperMesh enables tailor-made simulation of laminates. Hence number of experimental tests required will be less. Future Plans Optimization of composite structure is to find total number of plies, its thickness and fiber orientation using Optistruct. Conclusion From this study it is concluded that, the composite structure is safe as failure index is 0.22 for considered loads and boundary conditions. Altair HyperWorks Capabilities are effective to simulate composite structures with defined orthotropic material properties (HyperMesh), problem solutions (Optistruct) and result interpretation (HyperView). ACKNOWLEDGEMENTS The authors would like to thank Mr. Sanjay Kale, Head - Competence Services, and Mr. Gopal Phule, Design Manager, Citec Engineering India for their constant support and encouragement to present this paper REFERENCES [1] P.K.Mallick, "Fiber Reinforced Composite," CRC Press, Taylor & Francis Group. [2] A.T.Nettles, Basic Mechanics of Laminated Composite Plates, NASA Reference Publication 1351,1994 [3] Ashwani Thakur, Sandeep Sharma, Weight and structural strength optimization of the Bumper of a vehicle using Composite Material, International Journal of Aerospace and Mechanical Engineering, ISSN: , Sept