Mechanics of Composite: help needed

Replies

• 

  Rohan_sK

  Ok, we will make an attempt to solve this.
  
  We do not know what are the factors or properties that the tables give information about for the Epoxy and Glass.
  
  However it is given that the ratio of volume for glass to epoxy is 60%,
  
  Hence, g/e = 0.6
  
  g = ( 0.6 ) e
  
  Total Volume = g + e
  
  = 0.6 e + e
  
  = 1.6 e
  
  Hence,
  1.6 e = 125 x 10 x 0.0125
  
  e = 15.625 cm^3
  
  Hence the Volume occupied by the Epoxy is 15.625 cm^3.
  
  As the problem statement data, the change in volume of the Lamina will be caused only due to the exapnsion in the Epoxy as glass does not absorb the moisture.
  
  It is given that the coefficient of expansion for the moisture is the same for the thickness as well as the transverse directions.
  
  Therefore, dx = dy = dz ( if the coefficient has no units)
  
  This is the condition for the calculation of the change in volume.
  
  We need some relation or data for the density or weight to volume ratio for the epoxy. Is there any such informattion in the tables you mentioned.
  
  You have mentioned that the moisture absorbed is only 8% of the weight of the epoxy and is calcualted to be 0.12 gm
  
  The volume change will be,
  
  V+dV = (125+dx) x (10+dy) x (0.0125+dz)
  
  But as, dx = dy = dz, the change in volume will be dx.dy.dz
  
  = (dx)^3
  
  Therefore if the weight to volume ratio for epoxy is given in the properties table then the change in volume can be calculated.
  
  Or just check the units of the Coefficient Of Expansion of Moisture, is it something per unit volume , if so the answer can be calculated from there by substitutng the condition for volume change that we have worked out above.