Validation and modeling of aeronautical composite structures subjected to combined loadings: The VERTEX project. Part 2: Load envelopes for the assessment of panels with large notches

Abstract

One of the important issues in the certification of composite aeronautical structures is large notches. In this paper, tests are carried out on technological specimens under tensile, shear and combined loadings using the VERTEX test rig presented in the first part of this publication. Strong interactions between postbuckling and propagation of cuts are observed. The specifically developed FE-SDIC methodology presented allows a first dialog between calculation and testing. The Discrete Ply Modeling method is able to compute the onset of failure in such complex tests. New test responses called ''envelope curves" are proposed and are obtained by following a load path that allows the behavior of the notched structure to be validated for certification purposes. This methodology should eventually lead to a new vision of the test pyramid with the help of ''Predictive Virtual Testing" procedures.

Experimental and numerical analysis of unfolding failure of L-shaped CFRP specimens

“…In the first part of the present article, the "Discrete Ply Model" (DPM) is used to simulate the behavior up to failure of an L-shaped specimen. This approach was initially developed for impact simulations at the Institut Clément Ader [42][43][44][45] but was successfully extended to in-plane problems like open-hole tensile tests [46], scaling effects [47] or, more recently, to structural testing of large notches [48].…”

“…In this section, the "Discrete Ply Model" (DPM) [42][43][44][45][46][47][48] is recalled very briefly. This model was initially developed to simulate impacts on composite structures and makes it possible to model various types of damage: delamination, matrix cracks and fibre breaks, during a failure scenario.…”

Noninvasive multilevel geometric regularization of mesh‐based three‐dimensional shape measurement

“…This method, initially developed in the context of subset‐DIC, was recently extended to the context of global approaches . For instance, global SDIC was successfully used for the analysis of complex experiments such as structural tests . Before estimating the displacement measurement, SDIC requires a calibration phase aiming at determining the parameters of the cameras and the actual shape of the specimen.…”

Combined loadings after medium velocity impact on large CFRP laminate plates: Tests and enhanced computation/testing dialogue

“…Thus, in order to significantly decrease the huge number of tests and to gain a better understanding of the behavior of actual composite structures, industrials and academic researchers are looking to a virtual testing approach [13,14], which implies reducing the number of tests at coupon scale and developing more representative testing methods. For this purpose, the French National Research Agency funded the "VERTEX" program [15][16][17][18]. VERTEX is the French acronym for "Experimental modeling and validation of composite structures under complex loading".…”