Structural Flakeboards and Composites 

 VACUUM PRESSURE SOAK TEST 



3035 



CORE CONSTRUCTION 



AND 



VENEER THICKNESS 



( INCH ) 



3 -LAYER 



5-HOUR BOIL TEST 



ORIENTED 



RANDOM 



Figure 24-51. — Delamination of composite panels with single veneers on each face 

 after VPS test (left) and 5-hour boil (right). (Photo from Hse 1976.) 



In VPS tests, 1/10-inch veneer and two-ply faces resulted in least thickness 

 swelling (20.7 percent); 1/10-inch veneer applied singly to panel faces had most 

 swelling (30.0 percent). With 1/16- and 1/24-inch face veneers, litde difference 

 was noted between one- and two-ply construction. 



In the 5-hour boil, panels with one-ply faces consistently swelled more than 

 panels with two-ply faces; this was true for all veneer thicknesses. As in the VPS 

 tests, 1/10-inch veneer and two-ply faces resulted in least thickness swelling 

 (25.3 percent); 1/10-inch veneer applied singly to panel faces had most swelling 

 (56.4 percent). 



In panels with one-ply faces, random core orientation yielded least thickness 

 swelling. With two-ply faces, swelling did not vary significantly with core 

 construction, as follows: 



Face and core Thickness swelling 



construction VPS 5^hour boil 



--Percent 



Single veneer 



Random 24.6 47.8 



Oriented 29.7 52.4 



Three-layer 25.3 52.5 



Two veneers, cross laminated 



Random 22.5 30.8 



Oriented 24. 1 30.6 



Three-layer 22.8 30.6 



Panels with single-ply faces had best integrity if constructed with random 

 cores. After the 5-hour boil test severe delamination was observed in panels with 

 three-layer and oriented cores; delamination was less severe in such panels when 

 subjected to the VPS test (fig. 24-51). The superior stability of random cores is 

 further evident from figure 24-52. Three-layer and oriented cores exhibited 

 delamination and deformation. 



