6-8 



DESIGN OF LAMINATES 



The shear stress causes the following strains in the 1-1 and 2-2 

 directions respectively: 



m-. 



2 



■12 



"12 



(6.6) 

 (6.7) 



where : 



nv? = sin 2a 



°LT + 



Et i Et of Et E l \ 



E T 2 G LT V Lr Et G / 



(6.8) 



The shear stress x-, applied in the 1-1 and 2-2 directions causes a 

 shear strain: 



Yl2 



G 12 



and the shear modulus is obtained from: 



U LT _ ^MT 

 G 12 E L 



(i . a, lT • h) . (i . ,o LT . | - §-) 



cos^a 



(6.9) 

 (6. 10) 



Some of the physical constants which are important in structural analysis are as follows: 



Flexural Modulus = E feT and E™, where E hL is measured parallel to the warp and 



Eyp is measured perpendicular to the warp. 



Tensile Modulus = E.y anci ^tT measured as above. 



Compressive Modulus = E c ^ and E c rp measured as above. 



Flexural Stress = f^T and f feT measured as above. 



Tensile Stress = f^ L and f tT measured as above. 



Compressive Stress = f cL and f cT measured as above. 



Poisson's Ratio = ff strain in the transverse direction due to a load 



in the longitudinal direction, and ° ^, strain in the longitudinal direction 



due to a load in the transverse direction. 



Modulus of Rigidity or Shear Modulus = Gjjj>< 



