Validation and modeling of aeronautical composite structures subjected to combined loadings: The VERTEX project. Part 1: Experimental setup, FE-DIC instrumentation and procedures

The development and certification of aeronautical composite structures is still largely based on the pyramid of tests. This approach is extremely costly in terms of number of tests and design loops. Moreover, it is based on uniaxial tests whereas the real structures are mostly subjected to combined loadings. The aim of the collaborative research program “VERTEX” is to progress towards Predictive Virtual Testing and to significantly reduce the development costs of aeronautical and space programs. In this first part, the specific methodology for multiaxial tests of aeronautical structures is presented. The concept of the technological specimen and its size are justified. Then, the development of a specific test rig is presented, on which compression/tension, shear, internal pressure and combinations are possible. Since structural tests are complex to instrument, a specific full-field measurement technique is developed. It is based on a multi-camera instrumentation and an original Finite Element approach to Stereo Digital Image Correlation (FE-SDIC). Within such a framework, given that the very same mesh can be used for the simulation and the measurement, the corresponding displacements can be compared directly. In addition, a mechanical regularization of the FE-SDIC measurements allows mechanically consistent fields to be evaluated, such as displacement and rotation fields that could be used as boundary conditions in the simulations. The experimental procedure, the measurement methodologies and the calculation/test dialogue are validated on isotropic metal plates in this paper.