Appl. Sci. 2023 , 13 , 1389
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( a )
( b )
( c )
( d ) ( f ) Figure14. Shape of the edges of the compressed samples at the time of destruction for the connection length: ( a ) 0.7mm, ( b ) 1.3mm, ( c ) 2mm, ( d ) 3mm, ( e ) 4mm, ( f ) 5mm. 4. Discussion ( e ) The results of the measurements made it possible to draw a number of conclusions. For a length of 0.7 mm, the paper fibers delaminated and crushed near the fixed lower handle of the machine. In this case, the ratio of the length of the sample to its thickness is L/g = 5. For lengths of 1.3 and 2.0 mm, destruction shall also occur near the lower handle with visible horizontal displacement of the samples. For these cases, we have L/g = 9.3 and L/g = 14.3, respectively. For the fastening lengths of 3.0 (L/g = 21.4) and 4.0 mm (L/g = 28.5), the destruction of the samples takes place in the central part and the sample takes the shape of the letter V. Note that paper edges enter tangentially into both handles. However, for a length of 5 mm (L/g = 35.7), the V-shape is very clearly visible, in particular the refraction itself. The sample at the places of attachment to both handles takes the shape as for joint-like support. In the theory of thin-walled structures, the following classification is assumed: when L/g > 25–30, where L is a smaller overall dimension, the plates are thin-walled; when 5 < L/g < 25 the plates are of medium thickness, while L/g ≤ 5 the plates are thick [16,17]. According to this classification, the clamping length L = 0.7 mm corresponds to thick plates, and for L = 1.3, 2.0, 3.0, 4.0 plates of medium length, and for L = 5.0 thin plate. For plates of medium thickness, modifications are made in relation to thin plates [18,25,26]. Figure 15 shows diagrams of changes in the deflection arrow of the sample as a function of displacement of the movable handle of the testing machine with the place where the maximum force is reached.
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