The aim of the experiment is the experimental verification of FEM-models on a planar composite panel, using shearing load and determination of the buckling load.

Experimental set-up

The perforated shearing panel is clamped on all four sides into a steel frame, which has a joint in each corner and can thus create a pure shearing strain in the board. In order to deform the board, a force is applied to one corner of the frame.

Experimental data

Measurements of the shearing panel: approx. 600x600mm²
Free shearing area: approx. 500x500mm²
Thickness of the panel: 3mm
Measuring area: approx. 1 / 4 of the board (upper left-hand corner)
Grating pattern: stochastic pattern (sprayed onto surface)

Experimental results

If the images of the strain distributions in x- and y-direction are divided from the upper left to the lower right, then the extensive area of tensile strain in x-direction (positive strains) lies mostly below this diagonal. Its maximum is level with the upper edge of the punch-out in the shearing panel and reaches strain values of about 0.14%. In the distribution of strain in y-direction the area of tensile strain lies mostly above the diagonal and reaches values of up to 0.2%. In the lower right side of both images there is an area of strain, whose maximum reaches values of -0.24% and -0.18%.

In the image of the shearing there is an extensive area with low shear-values (0°) on the diagonal, that increase only towards the lower right corner of the image. The maximum shear reaches values of about 0.16° and lies in the area of maximum strain in x- and y-direction.

In contrast to the low strain values relatively large displacements in z-direction are measured. Here a buckling of the plate can be detected, with maximums of over 6 mm, which is due to the shearing stress. These values are in the same place as the maximum compression of the strain in x- and y-direction. If the measurement of the z-displacement is made at different load situations, the position of the buckling point can be predicted and the buckling time and load (i.e. the point of time when the shearing panel suddenly buckles) can be monitored.

The data measured here has been verified during some measurements using strain gauge strips and inductive sensors.

By courtesy of IFL TU-Braunschweig, Daimler Chrysler Aerospace, DLR