DESIGN OF LAMINATES 



6-79 



Shear modulus for woven roving, G^ = 0,U5> x 10° 



(Table 5-14) 



5 



88.0 x U8^ 



5.0 x U8 2 



Deflection, d = m —^—-^—^^ + - - ^^ ^ ^ q ^ g ^ ^ _ ^ 

 d = 1.1507 + 0.0386 = 1.2393 in. 



FLAT RECTANGULAR PLATES 



A laminate whose thickness is much smaller than its width and length can be classified 

 as a plate. The analysis of plate sections is both complex and lengthy because of the many 

 variables which enter into the configuration of a plate. The problem of plate analysis is 

 further complicated by the fact that plates can be either orthotropic or isotropic in behavior. 

 Most of the research to date has been based on isotropic materials, such as steel and alumi- 

 num. When a laminate behaves isotropically, such as a mat reinforced laminate, the 

 methods generally used for steel plates can be adopted. When the plate is made of materials 

 that produce an orthotropic laminate however, different approaches to the problem must 

 be used. 



During World War II, a good deal of use was made of plywood plate sections. Forest 

 Products Laboratory conducted a series of experiments and performed basic research on 

 this material to better understand its behavior. This effort led to several publications which 

 outlined methods that could be used for the analysis of plywood plate sections. Since fiber- 

 glass reinforced plastic laminates are, in general, orthotropic in behavior, it is possible to 

 use the approaches and formulas developed for plywood plates. In the final analysis, how- 

 ever, the results would have to be verified by actual experimentation. 



Plates can be subjected to many different combinations of loads, boundary conditions, 

 aspect ratio, etc. There are however, three basic configurations from which most of the 

 analysis begin; these are as illustrated in Fig. 6-43: 



A. Plates loaded in edgewise compression. 



B. Plates loaded in uniform shear. 



C. Plates loaded laterally. 



D. Plates loaded in any combinations of the above. 



Fig. 6-43. Loads 

 on Flat Plates 



PLATES LOADED LATERALLY 



a. PLATES LOADED I N 

 EDGEWISE COMPRESSION 



b. PLATES LOADED 

 UNIFORM SHEAR 



