A novel test load frame for characterizing the buckling resistance of thick sandwich panels

The latest design standards and guidelines for wind turbine rotor blades encourage model validation through sub-component testing, offering the incentive of lower material reduction factors. Structural stability, i.e., the buckling resistance, stands out among the critical design parameters. This aspect is crucial for the large, aerodynamic shell-like areas constructed from lightweight sandwich materials. In support of this model validation, our research introduces a novel test load frame designed to assess the stability of composite sandwich plates under quasi-static compressive loads. The load frame accommodates relatively thick plates with adjustable aspect ratios and aims to: (i) provide simply supported boundaries on all four edges, (ii) enable rapid installation of the specimen while accurately aligning the plate to the load axis, and (iii) allow for easy mounting in a standard universal testing machine. We successfully conducted a proof-of-concept test. For this purpose, a sandwich configuration consisting of glass, epoxy, and balsa wood was manufactured. It was tested quasi-statically to failure, while strains and out-of-plane deflections were monitored using a digital image correlation system. The critical buckling load was predicted using both an analytical orthotropic plate model and a finite element model, with the theoretical results overestimating the experimental values by 1.3% to 5.7%.