Page 222 - Mechanics Analysis Composite Materials
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Chapter 4. Mechanics of a composite layer       207




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          Fig. 4.79. A composite  leading edge of  an aeroplane wing made of carbon  fabric by  lay-up method.
                                      Courtesy of CRISM.


















                               Fig. 4.80.  Unit cell of a fabric structure.

         structure is shown the warp (lengthwise) and fill (crosswise) yarns forming the fabric
         make angle a 2 0 with the plane of the fabric layer.
           To  demonstrate  how  this  angle  influences  material  stiffness,  consider  tension
         of  the  structure  shown  in  Fig. 4.80 in  the  warp  direction.  Apparent  modulus  of
         elasticity can be expressed as

             E,A,  = EfAf + E,A,  ,                                        (4.165)

         where A, = h(2tl + t2) is the apparent cross-sectional area and

                  h                h
                   (2tl
             Af  = ; + t2),  A,  = Z(4tl + t2)
                  L
         are  the  areas  of  the  fill  and  warp  yarns  in  the  cross  section.  Substitution  into
         Eq. (4.165) yields
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