A brief discussion on (pure mode I) fatigue crack growth rate data in 5HS weave fabric composites: Evaluation of empirical relations

• Discussion on the region of stable crack propagation in a crimped surface.
• Adoption of the parameters of the modified Paris law equation based on fracture patterns.
• Explanation on how the crimp pattern may affect the decisions about the equation parameters.

A major concern in laminated composites for structural applications has been crack nucleation between plies and its propagation through the interface. A better comprehension of stable crack propagation may lead to more reliable predictions of the rate with which cracks grow in weave fabric laminated composites. To this aim, a number of empirical relationships proposed in the literature were studied for their applicability to satin weave fabric (5HS) composite with spread tows. In order to understand the fatigue delamination process, Double Cantilever Beam specimens were submitted to cyclic loading, and their respective da/dN vs strain energy release rate (SERR) data collected and correlated to these empirical relationships. Despite that the empirical or semi-empirical relations fit equally well to the data, the well-known Hartman–Schijve equation was adopted. This equation was properly modified according to the fracture surface investigation which had its fracture patterns qualitatively correlated with SERR parameters.