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Classical Laminate Analysis in Excel using FeResPost COM Component

Purpose of the excel workbook

The excel workbook discussed here illustrates what is possible to do with excel, VBA and FeResPost COM component. In this case one is particularly interested in classical laminate analysis capabilities of FeResPost. In this page, one presents the excel workbook usage, but not the programming of VBA code. Information on this VBA code can be found in FeResPost User Manual, and of course, you can read the VBA code with excel VBA editor.

The workbook we present here is provided with FeResPost COM example in "COMEX/EX06/LaminateAnalysis.xls" excel file. To run this example, you need to register properly the corresponding version of FeResPost COM component. The way to do it is explained in FeResPost Reference Manual.

Note that the excel workbook we describe here is used to perform Classical Laminate Analysis (CLA) with FeResPost in excel, without interaction with Nastran or Samcef finite element results post-processing. It allows though to import CLA entities from Nastran and Samcef FE models. But the reader should be aware that FeResPost's CLA classes are more powerful than what is presented here. In particular, they can interact with other FeResPost classes and be used in FEM results post-processing by for example:

• Calculating composite failure criteria from ply stresses or strains extracted from Nastran OP2, XDB or HDF5 files, or from Samcef DES&FAC files.
• Calculating ply stresses and strains from shell forces, shell curvatures, shell moments... also extracted from Nastran OP2, XDB or HDF5 files, or from Samcef DES&FAC files.

(This makes the CLA classes of FeResPost a very powerful tool for composite assessment in structure.)

Excel workbook

At the moment, we just present different worksheets that can be used to perform classical laminate analysis (CLA) calculations. (You can access the VBA code of the application via excel VBA editor, but we do not explain here how this code works.)

"ClaDb" worksheet

The "ClaDb" worksheet should be considered as the main worksheet of the excel workbook. Among other things, it allows you to:

• Import and export CLA entities (materials, laminates or loads):
• The difference between "importation" and "reading" is that reading is meant for an entire CLA database and that the previously stored CLA entities are removed before reading the new ones. On the other hand, the importation adds or replaces entities to the previous database.
• The importation can be done for an entire database, or only for materials, laminates or laminate loads.
• One can import CLA entities from a FeResPost neutral data file (NDF), from an ESAComp database, from a Nastran model or from a Samcef model. The Combo box in the spreadsheet allows the specification of the type of file one wants to read or import.
• The exportation of stored database can be done only in NDF file. This is done by clicking on "Save FeResPost NDF file" button.
• The list of available CLA entities (materials, laminates and laminate loads) is visible in the "ClaDb" worksheet.
• When you open the workbook, the list of entities is generally not empty:
• This is because a hidden spreadsheet called "NeutralLines" stores a database in NDF format, and the content of this hidden spreadsheet is read automatically when the workbook is open. (The spreadsheet can be made visible with excel VBA editor.)
• You can update the content of this hidden spreadsheet by clicking on "SaveDbToNeutralLines" button.
• On the other hand, by clicking on "RetrieveDbFromNeutralLines" button, you retrieve the previously stored composite database.
• When closing the workbook, excel proposes you:
• To export the current composite database in an external NDF file.
• To save the current composite database in the "NeutralLines" workbook.
• To save the current workbook.

If you want to retrieve the current composite database next time you open the workbook, you have to make sure that the two previous operations have been done. (Be careful with this because it is a common mistake to forget one of the operations.)

• You can remove entities stored in the database by selecting the corresponding range in the list of materials, laminates or loads and clicking on "Delete Selected Entities" button.

"MatEdit" worksheet

The "MatEdit" worksheet allows you to create or modify materials (ClaMat objects) in the composite database:

• The "Combo box" allows you to select a material existing in the composite database for examination or modification.
• The "Insert in DataBase" is used to insert the current material in the composite database. The inserted material is made active in the Combo box. If a material with the same ID already exists in the database, it is replaced by the new one.

 The edition of material properties is done by filling the lower tables in the worksheet:

• "Material ID" table allows to define the ID (string and/or integer identification) and the type of material (isotropic, anisotropic...).
• The columns "Moduli, CTEs, CMEs..." are meant to contain information related to the material stiffnesses, CTE, CME, thermal or moisture conductivity.
• The "Allowables" columns are devoted to the definition of allowables used in the calculation of composite failure criteria.
• The "Units" columns specify the system of units associated to the material and its data.

Note that the user is entirely responsible for the data inserted in the different tables. Data that can not be interpreted by FeResPost are simply ignored when the material is inserted in the composite database. User is referred to the description of "ClaMat" class and theoretical background in FeResPost User Manual to identify which data must be defined.

"LamEdit" worksheet

The "LamEdit" worksheet is used to create new laminates (ClaLam objects) or modify existing ones. The worksheet has three form controls:

• The "Existing Laminate Selector" Combo box is used to select a laminate from the composite database in order to modify it.
• The "Existing Material Search" Combo box is used to find materials existing in the composite database. This Combo box has been added to facilitate the identification of materials already defined in the database.
• The "Insert in DataBase" button inserts the defined laminate in the composite database. If a laminate with the same ID already exists in the database, it is replaced by the new one. The inserted laminate is made the active one in the "Existing Laminate Selector" Combo box.

The data defining the laminate must be introduced in the tables below the controls:

• When a new laminate is defined, it must identified with an integer/string ID.
• The reference temperature (refT) and moisture content (refH) can be defined. These values correspond to the temperature or moisture content at which the laminate is supposed stress free. (The use of temperature or moisture in laminate load response is optional.)
• The biggest table contains the definition of laminate layup. Each ply is characterized by:
• A ply ID (integer and/or string).
• A material identified by its integer and/or string ID.
• A thickness.
• An angle defining the orientation of the ply with respect laminate axes.
• An interlaminate shear stress (ILSS) allowable.
• One table is devoted to the definition of laminate allowables. It is the same table as for the material allowables. These allowables must be defined if one wants to calculate laminate failure criteria using laminate allowables instead of ply material allowables. (This is not very common though, except for strain cut-off or combined strain criteria for which the allowable is also often related to laminate thickness and not only to ply materials.) User is referred to the description of "ClaLam" class and theoretical background in >FeResPost Reference Manual to identify which data must be defined.
• As for material definition, you can define the system of units in which laminate definition quantities are expressed.

"LoadEdit" worksheet

The composite database also allows to defined and store "ClaLoad" objects. The "LoadEdit" worksheet allows to define or modify these "ClaLoad" objects. The worksheet has two form controls:

• The "Existing Load Selector" Combo box allows to select a ClaLoad object already defined in the composite database in order to modify it.
• The "Insert in DataBase" button inserts the defined load in the composite database. If a load with the same ID already exists in the database, it is replaced by the new one. The inserted load is made the active one in the «Existing Load Selector" Combo box.

The following data allow the definition of load object:

• A load ID (integer and/or string) must be associated to the ClaLoad object.
• The in-plane force or strain components are defined by three real values. 
• The bending moments or curvature components are defined by three real values. 
• The out-of-plane shear force or strain components are defined by two real values.
• Temperature and/or moisture content can also be considered in the definition of laminate loading.
• Finally, as for the material or laminate definition a system of units can be associated to the ClaLoad object.

For all the mechanical components of laminate loading, one can choose to define the component as strain or curvature, or as force or moment. This is the reason why a Combo box is associated to each component. The Combo box has two values: "SC" (strain/curvature) or "FM" (force/moment).

"DbUnitsEdit" worksheet

This worksheet allows you to modify the system of units associated to entities stored in the composite database. In the spreadsheet, one finds the following elements:

• The "Current Db Units" table gives the system of units associated to the current composite database. Note that this system of units is associated to the database, but not to all the entities stored in the database.
• The "New Units" contains the definition of a new system of units one wishes to associate to the composite database, or to entities stored in the database.
• Several Combo boxes allow to select the new units. This facilitates the choice of a valid unit for the different physical quantities.
• Several buttons allow to modify the composite database using the new units:

• The "SetDbUnits" button allows to associate a new unit system to the composite database. This button does not modify the units of entities stored in the database.
• The "SetUnitsAllEntities" and "ChangeUnitsAllEntities" allow to modify the systems of units associated to all the entities stored in the database (materials, laminates and loads).
• Then three "SetUnits*" and "ChangeUnits*" allow to modify the units of materials, laminates or loads separately.

Note the difference between the "setting" and "changing" of units:

• When units are "set", the numerical values of corresponding entities are not modified. This means that one really changes the physical quantities.
• On the other hand, when units are "changed", the numerical values associated to these units are converted. This means that the physical object  remains the same.

"MatProperties" worksheet

The "MatProperties" worksheet allows you to examine material properties:

• A Combo box allows to select a material defined in the database.
• A Scroll bar allows you to select an angle corresponding to the direction wrt which the different properties will be displayed.

Then, the following properties are displayed:

• The system of units associated to the material.
• The stiffness and compliance matrices.
• The CTE and CME properties.
• The thermal and moisture conductivity matrices.

"LamProperties" worksheet

The "LamProperties" worksheet allows you to examine material properties:

• A Combo box allows to select a laminate defined in the database.
• A Scroll bar allows you to select an angle corresponding to the direction wrt which the different properties will be displayed.

Then, the following properties are displayed:

• The system of units associated to the laminate.
• The stiffness and compliance matrices ABBD and abbd.
• The out-of-plane shear stiffness and compliance matrices G and g.
• The laminate thickness, surfacic mass and average densities.
• The CTE and CME properties.
• The thermal and moisture conductivities.
• A list of engineering constants.

"LamLoadResponse_A" worksheet

The "LamLoadResponse_A" worksheet allows the calculation of laminate load response and ply failure indices for a specified loading. The loading is selected among the loads stored in the composite database.

The calculation data are defined as follows:

• A Combo box allows to select a laminate stored in the composite database.
• A Combo box allows to select a load stored in the composite database.
• A Scroll bar allows to specify an angle corresponding to the orientation of the loading wrt the laminate.
• Three Combo boxes allow to specify whether ply results are estimated at lower face, mid-thickness and/or upper face of each ply.
• A Combo box allows to specify whether ply stress and strain results are given in ply axes, or in a coordinate system defined wrt laminate axes.
• A Scroll bar allows to define an angle wrt laminate axes. This angle corresponds to the coordinate system in which laminate stresses-strains are expressed, and ply stresses and strains if required wrt laminate axes.
• The spreadsheet allows to calculation of up to five failure criteria. For each criterion, three Combo boxes define the calculations data:
• The selected criterion.
• One can require failure indices, reserve factors or an equivalent scalar stress (when applicable).
• One can also specify whether the calculation of failure criterion is done with laminate or material allowables.
• For each criterion, a cell contains the safety factor used in the calculation of reserve factor.

The following results are calculated:

• The laminate in-plane and bending or out-of-plane shear stress-strain state.
• Ply stresses, strains and failure indices.

"LamLoadResponse_B" worksheet

This worksheet performs the same calculations as "LamLoadResponse_A", but the loading applied to the laminate id directly defined in the spreadsheet. One no longer selects a loading defined in the composite database.

The definition of loading is done by specifying the different components by filling the corresponding cells. Combo boxes allow to define whether the component is defined as shell force or moments, or as average strain or curvature. For the other data, please go to the description of "LamLoadResponse_A" worksheet for more information.

"LamMinMaxCalcArray" worksheet

In "LamMinMaxCalcArray" worksheet, one calculates critical (i.e. the value for most critical ply) failure indices, reserve factors or equivalent stresses, for several composite failure criteria and several load cases.

The calculation data are defined as follows:

• A Combo box allows to select a laminate stored in the composite database.
• A Scroll bar allows to specify an angle corresponding to the orientation of the loading wrt the laminate.
• Three Combo boxes allow to specify whether ply results are estimated at lower face, mid-thickness and/or upper face of each ply.
• The spreadsheet allows to calculation of up to five failure criteria. For each criterion, three Combo boxes define the calculations data:
• The selected criterion.
• One can require failure indices, reserve factors or an equivalent scalar stress (when applicable).
• One can also specify whether the calculation of failure criterion is done with laminate or material allowables.
• For each criterion, a cell contains the safety factor used in the calculation of reserve factor.
• A "MIN" or "MAX" value that specifies whether one wishes the most critical or less critical criterion.

(In the spreadsheet, that calculates the most critical ply, the "MIN/MAX" value is calculated by a formula that depends on the type of result that is calculated. Its result is "MAX" for equivalent stress, and "MIN" otherwise.)

The calculation is done by calling "calcPliesMinMaxCriterionArray" that returns a matrix that performs the array calculation by a single function call. Note that  a "LamMinMaxCalcArray" scalar version of the spreadsheet exists. In that version, each calculated value is obtained by a separate call  to "calcPliesMinMaxCriterionArray" VBA function.

References

More information on this example, and the manual explaining the functions used in this example are given in FeResPost Reference Manual.

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