6-80 



DESIGN OF LAMINATES 



Groups A, B, C and D can be further subdivided according to boundary conditions, that 

 is, free edges, clamped edges, or a combination of free and clamped edges. 



The designer, when analyzing plates, is usually interested in the critical buckling load, 

 bending stress and deflection. Formulas, methods, etc. have been established by which 

 these variables can be obtained for plywood (5, 13, 15-20). 



A. Plates Loaded in Edgewise Compression 



Mathematical procedures are available by which the critical buckling load for plates 

 under various edge conditions can be obtained (13, 15). The discussion presented here is for 

 loads applied parallel to or at 90 degrees to the warp direction, Fig. 6-44. 



WARP D1RECTIOI 



Fig. 6-44. Flat Plate 

 in Compression - Load 

 Parallel to Warp 



The following terminology will apply to plate analysis for edgewise compression: 



a = width of plate; = b 



b = length of plate 



h = thickness of plate 



n = number of half-waves into which the panel buckles 



E T = Young's flexural modulus in a direction parallel to the T-axis 



Et = Young' s flexural modulus in a direction parallel to the L-axis 



G TL = Modulus of rigidity associated with a shearing strain corresponding 

 to the axes of T and L 



a TL = Poisson's ratio associated with a contraction parallel 



to the T-axis and a tensile stress parallel to the L-axis 



olt = Poisson's ratio associated with a contraction parallel 



to the L-axis and a tensile stress parallel to the T-axis 



