Abstract
The first discussion of the buckling of plywood appears to have been made by Balabuch.1) March1) has also dealt with the problem both theoretically and experimentally. There have been many writers besides them who have contributed to finding methods in various ways for the buckling of plywood plates.
In many cases, the strain energy method has to be used. One of the few cases where an exact and simple solution is known is that of a simply supported 0° or 90° plate under unidirectional compression (P2=0, S=0 in Fig. 1). In this case, equation (4) reduces to the known accurate result (5). On the other hand, Norris has pointed out that the stress pcr at which the buckling first occurs can be written as equation (7) and the buckling stress coefficient kc is given in equation (8), where r is chosen to make pcr the minimun.
Previous experimental discussions have been limited to specific construction of plywood of equal veneer thickness.
In this report, plates of Lauan Plywood of various construtions as shown in Table I have been tested, and the observed values of kc have been compared with the calculated values. The values of kc is plotted against a/b(E2/E1)1/4. Examples of these curves are shown in Fig. 3 (a)-(g).
When a/b(E2/E1)1/4 is greater than 1, the value of kc is approximately independent of a/b, and kc(a/b→∞) which is defined as equation (10) which is arranged to (11) including Q(=EL/ET), A and D, where A and D depend on the construction of plywood. The effect of A and D on kc(a/b→∞) is shown in Table III, when Q is equal to 20.
E1 is Young's modulus of plywood parallel to the direction of compression (Parallel to the side a in Fig. 1), E2 is Young's modulus of plywood perpendicular to direction of compression (Parallel to the side b), EL is the longitudinal Young's modulus of the solid wood composing the plywood, ET is the tangential Young's modulus, and A is determined in formula (c), D is determined in (g), where tn are shown in Fig. 4.
