Experimental determination of validated, critical interfacial modes I and II energy release rates in a composite sandwich panel

A validated experimental approach to obtaining critical mode I and mode II energy release rates for interfacial failure in a sandwich composite panel is outlined in this paper. By modifying the geometry of the sandwich structure to align the face sheet-core interface to coincide with the neutral axis, it is possible to obtain critical mode I and mode II energy release rates by conducting Double Cantilever Beam (DCB) and End Notch Flexure (ENF) tests, respectively. The values so obtained were used to predict the crack growth histories of modified DCB and ENF tests, and a Single Leg Bend (SLB) test, using a discrete cohesive zone method (DCZM). In addition, the influence of material and geometry were also analyzed.

► We propose new coupon geometry for experimental determination of mode I & II ERR using standard test fixtures.
► We examine variation due to material and geometry using perturbation analysis.
► Modified coupon DCB and ENF tests are relatively insensitive to the variation in material properties.
► Modified coupon DCB and ENF tests are sensitive to variation in number of ply.
► Proposed geometry is independently validated using experimental and numerical method.
► If there is freedom to modify coupon, proposed method is effective compared to current complex test methods.