What is buckling?
A mode of structural response characterized by an out-of-plane material deflection due to compressive action on the structural element involved. In advanced composites, buckling may take the form not only of conventional general instability and local instability but also a microinstability of individual fibers.
How to calculate buclking in composite materials?
To calculate the maximum load at which the component will fail, the following equation is used:
- Pcr = Euler’s critical load
- E = Young modulus of alasticity of column material
- I = minimum area moment of inertia of the cross section of the column.
- L = unsupported length of column
- K= column effective length factor
Depending how the component is clamped at the ends, the K adopts different values, as it is shown in the following image:
As it can be seen, there exists some recommendations about the value K instead of using the theoretical value.
In composite materials, a tube or panel can suffer buckling. In the case of panels, it is important to analyze them correctly as have core material. This phenomenon is known as wrinkling: a form of local instability of the faces associated with short waves of buckling of the faces.
For sandwiches with corrugated or honeycomb cores, the core does not constitute a continuous support, which implies that, the buckling wave length must equal that of the length between the supports. The displacements of the faces are transmitted to the core in which they damp out rapidly in the thickness direction.
