B.C.T. compression load of a corrugated board box

When a corrugated board box manufacturer tries to develop a new box, one of the design problems he runs into is selecting the correct cross section of the corrugated board. This includes the type of paper and the shape and number of the different layers. The board should meet different design requirements such as the maximum number of stacked boxes. Sometimes the capacity of a box to resist the vertical loads derived from stacking is expressed in terms of the so called "Box Compression Test" (BCT).

From a designer's standpoint, it would be very useful to have a predictive tool that allowed the computation of the BCT number of a box, from the geometry of the box and the cross section of the boards, without the need to make a prototype. Such a tool would speed up the design process and would produce boxes close to the optimum for each particular application. The difficulties in developing a tool like this come from the anisotropic nature of paper, together with the geometrical nonlinearities of an assembly of thin sheets of paper.

The BCT is obtained by simulation of the compression test, with a speed of 10-13 mm/min in the press.

In our methodology, we work at two levels: the global (complete box) level and the local (board) level. The local level analyses the micromechanics of the board and produces macromechanical properties for the study of the box at the global level.

The flowchart describes our methodology. We have created a library with the macromechanical behaviour of different board configurations (different thicknesses and geometries). Using this library, we assign to each box prototype the properties of a corrugated board, so we can easily obtain the BCT number of the prototype.