S11-1 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation SECTION 11 INTRODUCING SPLITS IN THE PLIES

S11-2 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation

S11-3 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation n Fabric must shear to cover a doubly curved surface n The amount of shear distortion increases with increasing degree of double curvature and the area covered n The amount of shear is dependent on the starting point and initial fiber orientation n The material can shear up to a point at which the warp and weft (fill) fibers lock The point at which locking occurs varies with material and type of weave. A highly drapable material allows a large shear before locking. High shear during draping will lead to problems like wrinkling. In practice a laminator will introduce a cut(s) in the material to remove excess material. n MSC.Laminate Modeler introduces splits in exactly the same way INTRODUCING CUTS IN PLIES FOR CURVED COMPOSITES

S11-4 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation n Create/LM_Ply/Add u Additional Controls… l Boundaries l Define Splits n Select Curves and Edges n Preview Split u Preview the defined splits of the model to check if they are correct. The splits show up on both the model and the flat pattern. DEFINING SPLITS

S11-5 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation EXAMPLE: CREATING SPLITS The quarter section is by one ply, starting in the middle of the lower edge. The resulting shear is massive and totally unacceptable.

S11-6 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation By introducing two cuts, as shown below to the left, the resulting drape is much better. It could still need some more cuts in it. EXAMPLE: CREATING SPLITS

S11-7 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation By comparing the flat patterns, it can be seen that excess material is removed by introducing the splits. Without the splits, this excess material would have to be distributed by shearing the ply. EXAMPLE: CREATING SPLITS

S11-8 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation CREATING SPLITS, COMMENTS n Splits reduce shear in doubly curved plies n Splits makes any surface drapable n The best location for the splits is greatly dependent on the ply settings and the surface to be draped n May need to alter the menu settings in order to create an acceptable ply. These settings can be difficult to identify beforehand. Probably need to play around interactively in order to do this. Ask your laminator what he would do. n MSC.Laminate Modeler is a tool that enables you to do this n Note that splits do not add weak spots in the model, but remember that in real life splits must be staggered

S11-9 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation POSSIBLE DRAPING PROBLEMS n Sharp corners u Use split n Holes in Surfaces u The holes must be meshed(filled with elements), but the elements do not have to have a property. MSC.Laminate Modeler will automatically detect these dummy elements.

S11-10 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation n Incomplete boundary definition u Define artificial boundaries using split n T-Sections u Watch the element selection and surface normals POSSIBLE DRAPING PROBLEMS (Cont.)

S11-11 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation n Ply pattern(*) does not cover entire application region(**) n Increase step lengths u Step Length is distance between lines l Implicit: input is factor that is multiplied times MSC.Laminate Modelers estimate of step length l Explicit: input is value for step length POSSIBLE DRAPING PROBLEMS (Cont.) * **

S11-12 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation n An error and message file is created called.lm_msg. Investigate this file for further details. View it interactively as shown below. POSSIBLE DRAPING PROBLEMS (Cont.)

S11-13 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation n Perform Workshop 6 Draping With a Split in your exercise workbook n Be sure to ask for help on anything you dont understand EXERCISE

S11-14 PAT325, Section 11, February 2004 Copyright 2004 MSC.Software Corporation