6-176 



DESIGN OF LAMINATES 



Isotropic 



V = 6pa 



max r 



Shear force at center of side b: 



(6.75) 



Ortho tropic 



where 



a = deflection constant 



fl x and g = bending moment constants in X and Y directions 



6 = shear force constant 



K , K and K y = correction factors for deflection and bending 

 moments in orthotropic plates 



(Table 6-19) 

 (Table 6-19) 



(Table 6-19) 



Other symbols as previously defined. 



DESIGN EXAMPLE 6-26. ULTIMATE UNIFORM LOAD FOR WOVEN ROVING 

 LAMINATE PANEL WITH SIMPLY SUPPORTED AND CLAMPED EDGES 



Given a woven roving polyester laminate 12 in. wide by 24 in. long by 1/4 in. thick. 

 Find the ultimate unit load p, bending moment m x and bending stress f^ for the laminate 

 when simply supported and with clamped edges. 



Case 1. Simply Supported Edges 



a. Value obtained from Table 6-17 



p = 1.29 psi 

 m x = 22.00 in. -lbs. (not given in this text) 

 f b = 2070 psi 



b. Using the orthotropic method (5) for the unit load, p: 



El = E 3 



1.81 x lQt 



maximum allowable deflection 



2 x 1.0U = 2.08 



(6.66) 



From Fig. 6-50a, for a - 



E^ 



% value of 2.08 the value of K x is 1.02 



and w = 



and p 



,155 x 1.02 x p x 12** = 0.250 = 0#125 in# 



1.81 x 10 6 x 0.25 3 

 0.125 x 1.81 x 10 6 x 0.25 3 



0.155 x 1.02 x 12 



IT 



= 1.10 psi 



(6.64) 

 (6.65) 



