lesson 24 - laminate modeling - rev c - siemens plm …€¦ · ct2155_fmp112_s_3 – student guide...

CT2155_FMP112_S_3 – Student Guide for Femap 101 – v11.2 – Rev C

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Femap 101 for Femap v11.2 Slide 24 - 1

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Lesson 24 - Modeling Composite Layups with Femap

Purpose

This lesson provides an overview of modeling laminate composites with Femap

Topics

• Composite Materials

• Inter-laminate Shear Stress and Failure

• Femap Laminate Properties Creation and Editing

• Femap Composite Layup Creating and Editing

• Modeling Honeycomb Core Composites

• Post Processing Models Containing Composites


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Composite Materials

Composite materials:

• 2D Orthotropic materials are generally used for defining Laminate Plate elements

• Isotropic or 3D Orthotropic are used for Laminate Solid elements

For most applications, they are either:

• Unidirectional tape in a resin

• Bi-directional fabric in a resin


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Examples of Composite Material Tensile Strengths

Highlighted materials are commonly used materials in aerospace, marine and wind energy

• Specific material attributes should be obtained from the material supplier or by testing


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Composite A, B and D Matrices

In it’s simplest form, the equations for normal (N) and bending forces (M) on a composite shell is as follows:

The A matrix is the Extensional Stiffness:

The B matrix is the Coupling Stiffness:

The D matrix is the Bending Stiffness:

Note: tk is the thickness of the kth layer and is the distance from the mid-plane to the centroid of the kth layer


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LAMINATE PLATE Element Property

A Layup is required to define aLaminate Plate element property

Offset Bottom Surface – when used, thebottom layer of the layup is offset thedistance entered from the surface(s)meshed, otherwise, the midplane of thelaminate will be located on the meshedsurface(s)

• Overrides the Offset options in theAutomesh Surfaces dialog box

Options (see page 4-39 in the Femap Commands manual)

• 1..Symmetric – when used, you only need to define the bottom half of the Layup

User Tip: Use the same ID for the Laminate Plate Property and the Layup assigned for the property. This will make your model more consistent and make it easier to edit.


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Failure Theory – used to calculate laminate failure indices. NX Nastran supports the following (see NX Nastran User’s Guide, Chapter 24):

Hill – used where materials have equal tensile and compressive strengths

Hoffman

Tsai-Wu

Max Strain

LAMINATE PLATE Element Property - continued

Laminate Properties:

• N.S. Mass/Area – assign non-structural mass per surface area

• BondShr Allow – used to calculate interlaminarfailure indices

• Ref Temp

• Damping

Note: Additional failure theories are supported in Femap add-ins such as Femply.


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Setting the Material Angle for LAMINATE PLATEs

For Laminate Plate elements, assign the 0-degree ply material direction using the command Modify > Update Elements > Material Orientation

• View the material direction with the View Option, Element – Material Direction enabled


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LAMINATE SOLID Element Property

Similar to the LAMINATE PLATE Element, a Layup is required to define a LAMINATE SOLID element property

The Material Coordinate System’s X-axis is aligned with the x direction of the element’s plies

The Ply/Stack direction specifies the direction of the layup relative to the Material Coordinate System

Laminate Properties define:

• Bond Shear Stress Allowable

• Bond Normal Stress Allowable

• Reference Temperature

• Damping Coefficient


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LAMINATE SOLID Element Notes - continued

Isotropic or 3D Othotropic materials should be used for Laminate Solid elements

• Ply and bond failure theories and allowables are defined in the Ply/Bond Failure tab in the Define Material – ISOTROPIC or 3D ORTHOTROPIC dialog box.


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LAMINATE SOLID Element Notes

Use only one solid element in thickness for meshing since the pre-defined layup will be applied to the element

• The thickness of the solid element should be the same thickness as the layup, otherwise, every ply in the layup will have its thickness scaled by the ratio between the thickness of the layup and the thickness of the element:

• Ply Thickness = Layup Thickness / Element Thickness. e.g. A 2 mm thick total layup applied to two (2) 100 mmlong beams with a10 N End Load

• Top beam is 2 mmthick – lower beam is1 mm thick

Assign a Global Ply to each ply in a layup usedfor LAMINATE SOLIDs


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Composite Layups

A Layup is the Femap object that manages the stack up of multiple composite plies

• Practical limit of 5000 plies per Layup

A Ply has the following attributes:

• Ply ID (number)

• Global Ply ID – Used to designate a common ply ID used in all layups in a model

• Material

• Thickness

• Angle


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Global Ply IDs

A Global Ply ID is used to designate a single continuous ply in a model

• Layups can contain multiple Global Plies, however, a Global Ply can be assigned only once in a layup

• If a GPID is specified for every ply in a layup, Femap generates a PCOMPG card instead of a PCOMP and then the GPID results are generated by NX Nastran

Manage Global Plies with the Global Ply definition dialog box:

• Right-click the Layups object in the Model Info pane

• Click the Global Ply icon ( )in the Layup Editor dialog box

• Enable AutoCreate to create a new Global Ply when creating a new ply


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Creating and Updating an Individual Ply

New Ply - Once you have a Material, Thickness, and Angle specified, click this button to add the ply to the layup.

Update buttons - Once a ply has been added to the list, the definition of that ply can be updated using:

• Update Global Ply

• Update Material

• Update Thickness

• Update Angle


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Duplicating and Modifying Ply Sequences

Duplicate - the selected ply or plies are copied to thetop of the Layup.

Delete

Symmetric - the “mirrored” plies will be added to the top of the Layup in reverse order of selection.

Reverse - reverse the order of the selected plies based on the original position (i.e., the selected ply which was closest to the “Bottom of Layup” will now be closest to the “Top of Layup” in the list).

Move Up and Move Down

Rotate – modify the angle of the selected ply(s) by the angle specified

Copy and Paste – copy to the top of the current layup or another layup

Compute – compute the layup’s in-plane and bending flexural properties along with A, B and D (and inverse) matrices and display in the Messages pane


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Layup Editor – Layup Viewer

The Layup Editor dialog box has a Layup Viewer icon that launches the Layup Viewer.

Options to control display of:

• Thickness

• Ply Angles

• Titles

• Color

• Scale

The Copy icon pastes picture of thelayup to Windows clipboard


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Composite Layup Laminate Equivalent Properties

When the Entity Info pane is active, the Laminate Equivalent Properties are automatically calculated and displayed when a Layup is created or edited. These properties are updated continuously along with modifications to the Layup.

When the Entity Info window is not activated, selecting the Compute button in the Layup Editor dialog box will display the calculated Laminate Equivalent Properties in the Messages pane. These properties are NOT updated until the Compute button is reselected.


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Modeling Honeycomb Core Composites

There are two element type options for modeling Honeycomb Core Composites:

• Laminate

• Major limitation is that potential crushing of the core is ignored

• Use two (2) plies to model a core in order to calculate the maximum shear force at the core

• Shell – Femap has an API script to generate aproperty for the same type of layup

• Custom Tools > Honeycomb PSHELL >Honeycomb PShell Property


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Post Processing Laminate ModelsAvailable Output Vectors

NX Nastran generates results on a per-ply basis

• Output Vectors equivalent to a plate element –Normal, Shear, Major Principle, Minor Principle, Maximum Shear, and VonMises Stresses are available for post processing

• When a Failure Theory is specified in a layup, and additional Output Vector for the laminate ply failure index (Lam Plyn Fib Fail Index) is available for posting

• When a interlaminar bond shear allowance (Bond/ShrAllow) is specified, a ply n to ply n+1 failure index (Lam Bondn-n+1 Fail Index) is available for posting

Note: Ply X Normal Stress is always pointed in the ply fiber direction.

e.g. for a 45-degree ply, the X Normal stress is 45-degrees from the material direction.


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Post Processing Laminate ModelsGlobal Ply Data

Femap will create Global Ply ID (GPID) results on the fly without having to assign a GPID to every ply in a layup

• The Contour tool in the PostProcessing toolbox has a dropdown for Laminate Results From

• When no GPIDs exist in model, Femap can still use the Top Ply of Layup or the Bottom Ply of Layup for post processing

Note: You can assign Global Plies after an analysis is completed

• Use the command, Model > Output > Global Ply to generate output vectors for each GPID

• Does not generate output vectors for Top and Bottom plies of layups, just for assigned GPIDs


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Notes on Post Processing Laminate Results

For Strength Ratio Output Vectors, Enable SRCOMPS in the Nastran Bulk Data Optionsdialog box for Analysis Set(s) containing Laminate Shell or Laminate Solid elements

lesson 24 - laminate modeling - rev c - siemens plm …€¦ · ct2155_fmp112_s_3 – student guide...

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