3010 Chapter 24 



Random Oriented Southern pine 



Property flakeboard flakeboard plywood 



Density based on ovendry weight, 

 and volume at about 6 percent, 

 moisture content, pounds/cu ft 46.5 46.3 34.8 



Internal bond strength, psi 68 57 95 



Modulus of rupture, psi 



4-foot panel direction 4,200 3,400 1 ,900 



8-foot panel direction 5,600 5,600 8,800 



Modulus of elasticity, thousand psi 



4-foot panel direction 582 391 97 



8-foot panel direction 768 967 1 ,430 



These modulus of rupture and modulus of elasticity values were based on 

 specimen dimensions at test, after completion of the creep cycling procedure, 

 and after equilibration at 50 percent RH. Mechanical property values of stressed 

 specimens did not differ from those of specimens on which no load was im- 

 posed. Some of the plywood flexure specimens failed when the load was initially 

 applied, but none of the flakeboard specimens failed. 

 Price's'^ data suggest the following conclusions: 



• There was substantial variation among plywood panels in creep deflec- 

 tion in flexure and under concentrated load; three of the plywood 

 flexure specimens cut to represent the 4-foot panel direction failed when 

 initially loaded. Less variability was observed among flakeboard 

 specimens. 



• Creep deflections of the panel types were not sufficiently different that 

 one type could be selected as clearly superior to the others (fig. 24- 

 46BCDE). 



• Relative humidity cycles of 8 and 32 days caused greater creep deflec- 

 tion than 4-day cycles (figs. 24-46CE). 



• Specimen deflections after 32 days of 8- and 32-day cycles between 50 

 and 85 percent relative humidity were about twice those when intially 

 loaded (tables 24-25AB and figs. 24-46CE). 



