DESIGN OF LAMINATES 



6-75 



Figs. 6-39 and 6-40 give the same information for woven roving half-round stiffeners as 

 is given for hat stiffeners. The Figures provide for varying stiffener core diameter and 

 varying thickness of shell laminate for a given number of plies of woven roving in the 

 stiffener laminate. The effective width of the laminate is taken as twice the stiffener dia- 

 meter. Using "low average" ultimate stresses, as given in the physical properties tables in 

 Chapter 5, the critical bending stress will be in the compression face, cloth or woven roving 

 as the case may be for all stiffener sizes shown in these graphs. 



If a type C laminate is used, the section properties will be intermediate between those 

 given for types A and B laminates. 



DESIGN EXAMPLE 6-20. BENDING OF A STIFFENER AND PLATE SECTION 



The member whose cross-section is given in Fig. 6-41 has a span of 48 in. and is 

 simply supported. Compute the ultimate carrying capacity and deflection when uniformly 

 loaded. Assume all the plies of the various reinforcements to be parallel laminated in the 

 direction of the span and the core material is ineffective. 



4 PLI E5 25-27 OZ 

 WOVEN ROVING 



1 PLY 2 OZ MAT 



1 PLY 10 OZ CLOT 



h- 2" 



ASSUME 

 SECONDARY BOND 



Fig. 6-41. Composite Stiffener and Plate Section 



The necessary physical and mechanical properties for the different laminae are assumed 

 to be the same as for a laminate of the same reinforcement. The values are obtained from 

 Chapter 5. 



Property 

 Thickness, t, in. 



Cloth 



1 ply = 0. 016 



Mat 



1 ply = 0. 060 



W. R. 



4 ply = 0. 148 



Table No. 



5-1 



Tensile Modulus of 

 Elasticity, E, 1()6 psi 



1. 95 



0. 91 



2. 06 



5-7 



Ultimate Compressive 

 Stress, F c , psi 



18. 900 



15, 900 



15, 800 



5-11 



The transform area method and equations similar to those used in Design Example 6-19 

 will be used. 



Transforming the respective widths of the cloth and mat laminae to the equivalent width 

 of a woven roving lamina, the dimensions of the composite section will be as indicated in 

 Fig. 6-42. 



