Cyclic-fatigue crack growth in polymer composites: Data interpretation via the Hartman-Schijve methodology

Abstract

The European Structural Integrity Society (ESIS), Technical Committee 4 (TC4), has initiated a Round-Robin program on the Mode I delamination growth in a continuous carbon-fibre reinforced-plastic (CFRP) composite under fatigue loading, using Mode I double-cantilever (DCB) tests. The present paper shows that the Hartman-Schijve equation, determined with test data generated under R = 0.1, can be used to compute the fatigue crack growth (FCG) associated with tests performed at R = 0.3, 0.5 and 0.7, where R is the load ratio (=P_min/P_max). Most importantly, the Hartman-Schijve methodology may be used to determine a worst-case upper-bound da/dN versus $\Delta \sqrt{G}$ FCG curve for small naturally-occurring delaminations in the CFRP.