Fatigue Testing of fiber reinforced plastics

Measuring the fatigue behaviour of fibre reinforced plastics (FRP) is the key to predict service lifetime of parts and structures, whereat the anisotropic FRP show a very different behaviour from isotropic materials like metals. For FRP, fatigue is essentially created by initiation, growth and propagation of a multitude of cracks. The evolution of damage is influenced not only by the materials of matrix and fibres but also by the composition of the laminate. Although it is highly specific to the individual material, it usually follows the stages below:

  • Initiation of lateral cracks in laminate layers out of loading direction
  • Initiation of longitudinal cracks alongside load-bearing fibres
  • Delaminationen alongside rim of specimen
  • Internal delaminationen due to lateral and longitudinal cracks
  • Fracture of load-bearing fibres due to buckling
  • Delamination due to shear stress
  • Complete failure of the part/ specimen

We use a traction device for alternation loading (R=-1), tensile pulsation loading (R=0) or compression pulsation loading (R=-∞). The fibre direction configuration specifies the type of stress: longitudinal or lateral for tension and compression, +/-45° for shear tests. In order to prevent early fibre buckling, we use the Anti-Buckling Test Fixture GZ-BS32.

For characterizing the dynamical flexural material properties we use our 3-/4-Point Flexural test fixture GZ B-50. Here, too, tensile and compression properties can be investigated using fibre orientation.

We monitor the fatigue behaviour of the material of your choice, e.g. thermoplastics or thermosets, reinforced with carbon or glass long or continuous fibres, performing endurance stress/ operational reliability tests and generating “Wöhler” curves of your specific material configuration.