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      <title>Composite woven materials</title>
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      <div class="title_topic2" id="xps10_pagetitle">Composite woven materials</div>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('sheetmetaldes/wvn_ov.html');return(false);">Woven Materials Flattening Overview</a></p>
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               <p class="para_td">How To</p>
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               <p class="para_td"><a class="links" href="javascript:void(0)" onclick="top.openFile('sheetmetaldes/wvn_surface.html');return(false);">Options</a></p>
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      </table><br><p class="para_topic">An exact solution for the flattening of complex surfaces requires a detailed knowledge of both the properties of the material and the forming process itself. This information can be expressed in terms of partial differential equations requiring finite element methods for their solution. The process is both expensive and extremely time consuming, requiring resources beyond those justifiable for the end results.</p>
      <p class="para_topic">The woven materials approach bypasses these requirements by giving particular consideration to specific forming processes and by employing solutions within the accuracy of engineering tolerances. The application handles any single surface definable by NX.</p>
      <p class="para_topic">The basic approach the <b class="uiTerm">Flat Pattern</b> function uses for woven materials is to create a grid of curves having quasi&ndash;orthogonal (near right angle) directions over the surface. Nodes on this grid represent crossing points in the weave of the woven material. The interlaced strands following these directions are called the woof (horizontal) and warp (vertical) of the material.
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      <p class="para_topic">Using a starting point you define, the woven materials algorithm traces out the paths of the strands on the surface to be unformed. For woven materials it has proven accurate to assume that the material can be worked onto the surface by skewing the intersection of the strands at the various nodes and keeping the distance constant along the strands between the node points.</p>
      <p class="para_topic">The woof and warp strands of the original material are all at right angles to each other, as shown below. The unformed material is laid over the forming surface and a start point selected. The woof and warp strands remain normal to each other in the near vicinity of this point.</p>
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      <div class="title_figure">Biaxial cloth model</div>
      <p class="para_topic">The woven materials algorithm traces out the paths of the strands on the surface of the part. For woven materials, the system assumes that the adjacent strands of the pattern will deform to equal sided quadrilaterals as shown in the figure below. The result of this operation is that a set of points, through which the various strands pass, are generated (but not displayed) on the surface.</p>
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      <div class="title_figure">Quadrilateral material distortion</div>
      <p class="para_topic">By summing the distance along each strand to the boundaries of the surface, the system determines the length of the strands. These lengths are then mapped to the grid of the original unformed material, giving a close approximation of its unformed outline. The outline of the unformed part is defined by the trajectory of the strand end points mapped to the flat pattern X&ndash;Y coordinate system.</p>
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      <div class="title_figure">Formed and flattened surfaces&nbsp; </div>
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