6-188 



DESIGN OF LAMINATES 



u y Z ■ cG yxc 



*m 



'fv 1 ^ 



B 1 C 1 + 2B 2 C 2 + sf + A 



h C l + 2B 2 C 2 + gj 





1 + 



B-^C, + BoCg 





fj 2 - + B ^ c 



Bi 3 2 



V V 



Values of K f and K_ above are applicable for deflection when 

 n = 1 and the length to width ratios 



-| 1 



Ss IT 



LDyJ 



is within a range of 0.71 to l.U. 



Also when the core is considered effective, Kf = 



V. 



x 



p x Qyxf + 2Dxy 

 \/ D X Dy 



D _£L_ 



b 



~2~2~ 



n a 



C 2 - lj 



n 2 a 2 



where n = number of half -waves and equal to 1 in the 

 equations for Kf and K m above. 



= h o 3 



B 2 C 2 

 2 2 



+ B.C BC +2BC + ^- 

 3 2 V 1 1 2 2 Bn 



These equations have been applied to a sandwich panel in order to compare the results 

 with those obtained by simpler methods. The panel was taken as 24 in. by 24 in. , composed 

 of a 1 in. thick core, and 1/8 in. thick facings. The facings were considered to be of 10 ounce 

 fiberglass cloth-polyester laminate. Two different core materials were evaluated; balsa wood 

 of 4 lbs. per cu. ft. density and an isotropic low modulus material similar to a foamed resin. 

 The material properties assumed are given below: 



