6-178 DESIGN OF LAMINATES 



The above results are in good agreement and any of the methods of analysis discussed 

 is considered applicable. 



Case 2. Clamped Edges 



Using the orthotropic method (5): 



b 

 From Fig. 6-50a, for a value of -g 



the value of K2 = l.oU. 



and the unit load is: 



El 



1 



^ = 2.08, 



0.125 x 1.81 x 10 6 x 0.25 3 r (6.70) 



P = ■ r = 5.30 psi 



0.031 x l.Oh x 12 u 



Plates with Large Deflections: When the deflection of a laterally loaded plate equals 

 several times its thickness, the formulas developed for plates with small deflections cannot 

 be used. March (18,20) has developed expressions which can be used to give approximate 

 values for load, deflection, bending stress and direct stress. Only the conditions for a 

 uniformly loaded plate with simply supported and clamped edges are presented in this text. 

 Fig. 6-47 and the symbols previously defined are applicable to this discussion. 



Case 1. Simply Supported Plates Under Uniform Loads 



For a plate that is uniformly loaded and whose edges are simply supported, the follow- 

 ing formulas can be used to determine approximate values of the various factors of the plate: 



Maximum bending stress: 



f b = _^_ (6.76) 



i»a 



Mean direct stress: 



f _ S l hV 0? 2.572 E x w 2 (6.77) 



a " 3\ a 2 Xa 2 



Total maximum stress: 

 f total = f b + f a 



