In-plane compressive strength and failure behaviors of composite sandwich structures for wind turbine blades

Composite sandwich structure, as the largest part of wind turbine blades, often experiences complex failure phenomena during full-scale blade testing and wind farm operation. In order to better understand failure behaviors and reveal the failure mechanism of sandwich structures for wind turbine blades, composite sandwich samples were designed, fabricated, and tested in consideration of the real laminate and core machining configuration, manufacturing process, and dominating load of wind turbine blades, In -plane compressive strength and failure behaviors were investigated by experimental and theoretic methods. It was found that the grooved with perforations and cut (GPC) machining configuration can improve in -plane compressive strength of sandwich samples more than that of the double grooved with perforations (DGP) configuration due to higher core shear modulus, the failure mode of sandwich samples shifted from global buckling for Plain configuration to a combination of core shearing and skin/core debonding at both sides for DGP configuration, and finally to skin/core debonding at the shallow groove core side for GPC configuration. The failure mode of sandwich samples with DGP core mainly transferred from global buckling to a combination of core shearing and skin/core debonding at both sides, and further to skin/core debonding at both sides alone with increasing foam density. All samples with GPC core exhibited skin/core debonding at the shallow groove side after slight buckling, which was driven by the asymmetric structure of the GPC core. Classical methods can reasonably predict failure loads of sandwich samples with Plain and DGP cores, but overestimate that of sandwich samples with GPC core.