S15-1 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation SECTION 15 OPTIMIZATION OF COMPOSITES USING MSC.NASTRAN

S15-2 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation

S15-3 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation COMPOSITE OPTIMIZATION n What can optimization do? u Design improvement u Making infeasible designs work u Correlation with test u Identify sensitive design areas n NOTE: optimization of composites is not supported in either pre or post in MSC.Patran or MSC.Laminate Modeler before Patran It is only possible to do it through manual editing of the MSC.Nastran input file.

S15-4 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation DESIGN MODEL AND ANALYSIS MODEL n MSC.Nastran optimization uses a standard MSC.Nastran model which is called the analysis model n In addition a design model is created to specify how the optimization will occur. This consists of u Design variables, i.e. thickness, ply angle, etc. u Design responses, i.e. mass, stress, displacement, etc. u Design objective: one design response which can be minimized or maximized. Commonly minimize mass. u Design constraints: limits on design variables or responses, e.g. 5 < var1 < 10

S15-5 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation COMPOSITE OPTIMIZATION VARIABLE n Problem u Using ply angles as design variables can result in instability in the optimization routines due to low sensitivity n Solution u Model with plies at different angles, and assign a design variable to the thickness of each ply. u Use discrete optimization to ensure that the ply thicknesses obtained are available for the ply materials. u Use the thickness of each ply to decide how many plies will be needed at each angle

S15-6 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation EXAMPLE: OPTIMIZATION n 1323 nodes, 1392 elements n 21 property entries n 84 design variables n Minimize mass n Static pressure loading n Constraint on failure Indices

S15-7 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation EXAMPLE: OPTIMIZATION

S15-8 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation FAILURE INDEX RESULTS Initial Design Final Design Mass: 500 Mass: 200 Max failure index: Max failure index: 0.987

S15-9 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation SETTING UP OPTIMIZATION IN MSC.PATRAN n Optimization set-up in MSC.Patran is done from the Tools pull-down menu n Capabilities are more limited than Nastran but this is a good method to create a template analysis deck which can be edited by hand n Tools/Model Variables… u Creates design variables u For composites set Method: to Material u Set Category: to Composite u Variables can be l Thicknesses l Orientations l Both u Select the materials you want to change u Select the plies you want to change u Apply n In MSC.Laminate Modeler use the Expand/Laminate operation to have one property per element u This can result in very large optimization runs

S15-10 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation CREATING A DESIGN STUDY n Having created the design variables, now can use them for a design study n Tools/Design Study… u Give design study a name u Modify design variables, including limits u Design objective currently can only be to minimize weight u Specify constraints on response(e.g. displacement) u Apply to create a design study n Multiple design studies can be created, but only one can be used at a time

S15-11 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation n Modify design variables as needed n This form is opened by selecting Design Variables… n Allows changes to upper and lower limits for design variables u Defaults are 90% and 110% of starting value CREATING A DESIGN STUDY (Cont.)

S15-12 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation n Constraints on response can be specified for solutions for linear statics or normal modes n This form opens by Design Constraints… n Constraints can be for any of the following u Displacement l Components or magnitude u Stress u Strain u Element Force u Ply stress u Ply strain u Failure Index u Natural Frequency CREATING A DESIGN STUDY (Cont.)

S15-13 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation n Having defined a design study, the next step is to set-up to run an optimization problem. n In the Analysis menu set Action: to Optimize n In Translation Parameters… set Data Output to OP2 u This provides more optimization data to MSC.Patran n In Optimization Parameters… menu set DESMAX to maximum number of design iterations wanted u Default of 5 is often not enough CREATING A DESIGN STUDY (Cont.)

S15-14 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation n Run the optimization problem under Analysis: Optimize/Entire Model/Full Run n Having set up subcases they must be selected n Subcases can be for SOL 101 (linear static) or SOL 103(normal modes) CREATING A DESIGN STUDY (Cont.)

S15-15 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation n When OP2 results are read the design history is read into XY Plots n These results are not available from XDB files n 3 Plots can be posted from the XY Plot form u Design variable history u Maximum constraint history (should be at or below zero at last design cycle) u Objective function history CREATING A DESIGN STUDY (Cont.)

S15-16 PAT325, Section 15, February 2004 Copyright 2004 MSC.Software Corporation n Model properties can be updated to the optimized design in the design study u Open the design variable sub-form u Click on Design Cycle Select… button u Select RUN 1, and the last design cycle u Click OK on both sub- forms u Apply under Design Study menu n All model properties are then updated CREATING A DESIGN STUDY (Cont.)