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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Modeling Composites withModeling Composites with Femap 10.1.1

    An Introduction to The Hows and Whys

    George Laird, Ph.D., P.E.

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Table of ContentsTable of ContentsDefining a Laminate Material in Femap .....Femap Layup Editor ...Orthotropic Materials Overview ..

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    Defining an Orthotropic Material in Femap ...Example 1: Creating a Submarine Laminate Model in Femap ...........

    Creating the Laminate Material ..Defining the Laminate Layup D fi i th L i t P t

    681011 12Defining the Laminate Property .

    Specifying Material Angles Post Processing the Results

    Using Plate Elements to Model Honeycomb Core Composites .Classical Plate Theory Applied to Honeycomb Composites ..

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    The Nastran PShell Property Card ..Using the PShell Property Card for Honeycomb Composites Using Femap to Setup a Honeycomb Panel

    Example 2: Comparing Different Laminate Modeling Methods ....i l i d i h l

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    d Material Properties used in the Example Honeycomb Model using Solid Elements with Laminate Face Skins Honeycomb Model using Classical Plate Theory ...Honeycomb Model using Laminate Elements Results Summary .

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    Conclusion ..3435

  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Defining a Laminate Material in FemapDefining a Laminate Material in Femap

    To define a Laminate Material in Femap, 3 specifications must be made: The Composite Layup that is to be used must be specified Theseused must be specified. These Layups are defined using the Layup Editor. A Bond Shear Allowance must also be specified. The value represents the bond strength between the bonded laminate sheets. This value is used to calculate a factor of safety against shear failure between laminate panels.

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    pa e s. A Failure Theory must also be specified. If Tsai-Wu is specified, then the Tsai-Wu interaction coefficient must also be specified in th t i l d fi iti

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Femap Layup EditorFemap Layup Editor

    Th l dit i FThe new layup editor in Femapallows for the easy specification of laminate configurations. This new editor allows plys to be be edited individually or collectively. It also y yallows each ply to be moved around in the layup, as well as easy editing of ply thickness and angle.

    A compute button has also beenA compute button has also been added that allows the user to calculate and display the A, B and D matrices which represent the laminate behavior. These matrices are

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Orthotropic MaterialsOrthotropic Materials

    Often times Composites can be modeled as Orthotropic materials. The Nastran Mat8 material pcard can be used to simulate orthotropic behavior.

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    d The above is an example of an orthotropic material. The 1 direction could corresponds to the x direction and the 2 to the y or vise-versa. When deciding which direction is the x and which is the y, what is important is that the chosen convention is adhered to.

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Defining an Orthotropic Material in Femap

    FEMAP requires the entry of 5 values:

    Defining an Orthotropic Material in Femap

    values: 2 Youngs Moduli for the materials primary directions. A 1-2 Shear Modulus 2 Transverse Shear Moduli, 1z & 2z The 1-2 Poisson Ratio, the 2-1 Poisson Ratio is not required. The symmetry of the material stress tensor allows FEMAP to calculate it based upon E1 E2 and v1-2based upon E1, E2 and v1-2.

    There are a number of other values that can be entered depending upon what type of analysis is going to be

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    1) HMS B1-002 TY I-TSOne of the more difficult aspects of working with composites is

    i li i bl i l d i k ki hgetting realistic, usable material data. Matt Piatkowski at Heath Tecna inc. provided an example of a material model they have developed.

    These values were derived through correlating experimental data with FEA models. Built into this material model are a number of

    2) Graphite Tapeassumptions: it is only valid for certain shapes and loading schemes. The model works well in pure flex, but does not work well when a lot of shear or twist is imposed on the structure.

    Such limitations and assumptions are very important to quantify. An

    3) HMS B3-001 TY4 CL1 GR9

    FEA model is only as good as the assumptions that go into it.

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Example 1: Creating a Submarine LaminateExample 1: Creating a Submarine Laminate Model in Femap

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    The model to the right is a section of the submarine model shown on the previous page. The original model was built using plate elements, but in this example we will modify it so that the submarine skin is a laminate.

    The port is composed of solid elements, with an assumed material of steel. The ring of blue elements around the port are plate elements, whose purpose it is to simulate a weld. These plate elements are also

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Creating the Laminate MaterialCreating the Laminate MaterialThis model will use a single material for the laminate plies. The properties are those of a Graphite/epoxy composite.

    The Limit Stress/Strain section i d f l l i f ilis used for calculating failure indexes. There are a number of indexes Nastran will calculate: Hill, Hoffman, Tsai-Wu, and

    i S i iMaximum Strain. Tsai-Wu requires a material dependant experimentally derived value, it is in the material definition that hi l i ifi d

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    d this value is specified.We will use Hoffmans criteria, so this value isnt necessary for our analysis.

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    Jones, Robert M. Mechanics of Composite Materials. New York: Hemisphere, 1975. 70.

  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Defining the Laminate LayupDefining the Laminate Layup

    After the orthotropic material is created the Layup Editoris created, the Layup Editor can be used to define how the laminate plies are situated.

    The laminate that has beenThe laminate that has been defined on the right consists of 7 plys, each 0.2 inches thick. The primary direction of the plies varies by 90plies varies by 90 .

    This is a fairly simple configuration. Often the individual plies are different

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    d individual plies are differentmaterials, the top and bottom plies being composed of a somewhat tough material while the inner plies are more light-weight. Configurations such as these impart a large area moment of inertia while remaining light weight.

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    Defining the Laminate PropertyDefining the Laminate PropertyWe are now just a short jump away from having a laminate property defined. The laminate definition requires the user to specify which Layup will define the the laminate.

    The BondShr Allow also needs to be specified if a bond factor of safety is desired. The valuei i d b di idi h i l h b h dSh Allis arrived at by dividing the inter-ply shear stress by the BondShr Allow.

    It is here that the Failure theory is also specified. This example will use Hoffmans theory. These failure theories produce failure indexes. An index greater than 1 denotes failure. Each

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    d ply in the laminate will have an associated failure index. The equation used to calculate the Hoffman index is shown below.

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  • Predictive Engineering Femap 10.1.1 Composites Tutorial

    After the elements are Specifying Material Angles

    assigned the laminate property, they need to be given a specified angle that corresponds to the primary direction of the layup. The above picture specifies the directions we are interested in specifying. The ring of two elements around the port are to have an orientation tangent to the edge of the port, while all other elements need to point in the vertical direction.

    Going to Modify-Update

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