2986 Chapter 24 



Discussion in this text will be limited to performance under impact loads of 

 phenolic-bonded structural flakeboards made of southern hardwoods by the 

 procedure suggested by Hse et al. (1975), and as described in the footnotes to 

 table 24-12. The test procedure and results that follow are taken from Price 

 (1978). The procedure is described in some detail so that results may be more 

 readily interpreted. Both 1/2-inch and 5/8-inch panels satisfy impact require- 

 ments for APA RATED STURDI-FLOOR and APA RATED SHEATHING. 



Procedure. — Six 4- by 8-foot flakeboard panels from each density group 

 indicated in table 24-19 were used for impact evaluation. These were compared 

 to 19 southern pine plywood panels of two thicknesses (1/2-inch with three plies 

 and 5/8-inch with four plies) purchased from six building suppliers in central 

 Louisiana. A 1/2-inch and 5/8-inch panel from each supplier was randomly 

 selected for impact evaluation. 



All 1/2-inch panels were cut into 4- by 4-foot sections; 5/8-inch panels were 

 cut to obtain one 48- by 32-inch piece from each end. One section was used for 

 dry test (50 percent RH condition). The other section was designated for a 3-day 

 water spray applied to the top surface before evaluation. 



All panels were nailed to nominal 2- by 8-inch, kiln-dried, No. 2 (or better) 

 grade, southern pine framing; the 8-foot dimension of the panel spanned the 

 framing members. Panels were attached with 8d common nails spaced about 6 

 inches on center and about 3/8-inch from the edge along outside framing mem- 

 bers. Nails were 12 inches on center on the middle framing member. A nominal 

 1- by 4-inch board was nailed to the lower part of each end of the frame to 

 prevent rotation of the structure. 



All 1/2-inch panels were evaluated on 24-inch spans; the 5/8-inch panels were 

 evaluated on 16-inch spans. 



Impact locations were at mid-span 6 inches inward from the edge. A 200- 

 pound load was applied to a 3-inch disk at the designated impact location before 

 each drop of the impact load and after failure. The deflection resulting from the 

 concentrated load was recorded relative to the joist. After removal of the concen- 

 trated load, a leather bag containing enough No. 9 lead shot to total 30 pounds 

 was released by a remote-controlled solenoid-activated pair of jaws. The drop 

 bag conformed to ASTM E 72-68 (American Society for Testing and Materials 

 1968a). The first drop height was 6 inches and height was increased in 6-inch 

 increments until the panel would not support the 200-pound load or a failure was 

 observed. The maximum drop height (MDH) was recorded, and the deflection 

 caused by each drop was recorded relative to the joist. 



Results. — Price (1978) found that southern pine plywood had greater average 

 impact resistance than any of the flakeboard panels (table 24-19). However, 

 yellow-poplar flakeboards that were wet tested had a higher impact resistance 

 than plywood that was wet tested. Only the 1/2-inch oriented mixed species 

 flakeboards had a deflection at maximum drop height that was less than that of 

 plywood. 



Considerable variation was observed in the impact resistance of different 

 plywood panels and between locations on one panel. For instance, the 5/8-inch 

 plywood that was dry-tested had an average MDH on the inside edge of 56 

 inches (range of 1 8 to 90 inches) and an average on the outside edge of 84 inches 



