DESIGN OF LAMINATES 6-2 7 



Find: the ultimate load carrying capacity intension of the composite laminate per inch of width. 

 Using equation 6.13b, the strain in each layer can be found: 



Since the strain in all layers must be equal 



e m = e cl = F WR or 



F J1 = lcl= F M or 

 Em E cl %R 



F cl F WR 



fa) F = E x sr^ = E x ^ 



F m _ £cl 



(c) & ffi - E vffi x — - E^ m x E ^ 



Values for Ft, are selected from Table £-6 and values 

 for E t are selected from Table £-7 as follows: 



Mat Cloth Woven Roving 



F t = 6600 psi 17,900 psi 23,000 psi 



E t =0.90 x 10 6 psi 1.1+0 x 10 6 psi 1.3U X 10 6 psi 



Substituting the values for the stress F in the left hand portion of equations (a), (b) and 

 (c) above, the following relative stresses are obtained: 



, £ c -\ /_ fwR 



(a) 6600 psi = 0.90 x 10° x , —? = 0.90 x 10° x — —7 



l.UO x 106 1.3U x 106 



from which f cl = 10,267 psi 

 % = 9,827 psi 



