6-180 



DESIGN OF LAMINATES 



a 



h 



cosh n, 



coshr 



1-2 



cosM-l 



(6. 85) 



coshri 



The value of a can be obtained from Fig. 6-?lb. 



The above expressions are applicable when the ratio of 

 1 



u 



a a 



E 2 



1.5. 



In the solving of problems with the above equations it is suggested that the unit load, p, 

 be known or assumed for a specific laminate and the deflection, w, computed. Knowing w, 

 the values of r\ and a can be established. Finally the bending and direct stresses can be 

 determined. 



REFERENCE 20 



a. SIMPLY SUPPORTED EDGES 



CLAMPED EDGES 



Fig. 6-51. Coefficient a as a Function of r\ for Uniformly Loaded Flat Rectangular Panels 



SANDWICH CONSTRUCTION 



A structural sandwich may be defined as a combination of strong, high density, thin 

 facings with a relatively weak, low density thick core. The obvious purpose of such an 

 arrangement is to increase the rigidity and strength of a thin plate with a minimum increase 

 in weight. 



The theoretical analysis of sandwich construction, particularly sandwich construction 

 with orthotropic materials is a lengthy process and the theory is far from complete. The 

 theoretical analysis which has been done has generally resulted in expressions which are very 

 cumbersome and tedious to evaluate. In addition, some of the necessary elastic properties of the 



