Materials 2022 , 15 , 663
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( a )
( b )
( c )
( d )
( e )
( f )
Figure 12. The difference in BS between the EB and BE configuration: ( a ) Board 1; ( b ) Board 2; ( c ) Board3; ( d ) Board4; ( e ) Board5; ( f ) Board6. The difference in bending stiffness between the EB and BE configurations can be as high as 25%. However, this applies to cross-sections in which the imperfection amounts to 1% of the initial length of the compressed segment, L i . In our case, the initial imperfection, for the selected value of the k -factor, is 0.5% of L i . The practically zero difference between EB and BE case can be observed for the coefficient k equals to 3, i.e., initial imperfection equals to 0.1% of L i . Table 5 gathers all bending stiffness values for all 6 boards determined from experi- mental data [29], theoretical model (no imperfections), simplified FEM model (2D beam model—no imperfections), full 3D shell FE model [29]—no imperfections, and proposed here analytical model with imperfections.
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