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Fracture mechanics

Increasing the reliability of parts with fracture mechanic methods
Individual components of a structural part are often bonded with an adhesive agent. Although this type of bonding is quite easy to do, it is nevertheless a complex structural aspect of stability assessment:

  • The stiffness of the part in question can change abruptly along the bondline edge. This can lead to significant increases in the effective tension and may cause the bonding to fail.
  • Thick bondlines can lead to inhomogeneities, e.g. cavities, in the adhesive layer. The edges of these cavities will, in turn, be subjected to a local increase of tension, possibly resulting in a cohesive breakdown within the bondline.
  • Should a cavity occur at the contact point with the part, the bonding may fail there.
The failure mechanisms described are triggered by local effects. As such, fracture mechanics are particularly suitable for describing the stability of bondings.

Leichtwerk AG applies the following approach to bondings analysis:
  1. All bondings are generally considered to be predamaged; i.e. some type of flaw is assumed to be present.
  2. Application of an in-house procedure for experimental determination of fracture mechanic failure properties.
  3. Application of an in-house procedure to calculate the fracture mechanic conditions to which complex parts are subjected.