Characterization of MSD in emerging metallic structures in fuselage lap joints

icaf2023 Tracking Number 101

icaf2023 presentation

In partnership with Arconic and Embraer, the Federal Aviation Administration (FAA) is evaluating the behavior of multi-site damage (MSD) for emerging aluminum alloys in a generic fuselage lap joint configuration. This program is a comparative study of the initiation and growth characteristics of MSD for two aerospace aluminum alloys, namely: 2524-T3 aluminum-copper alloy (baseline) and 2060-T8 aluminum-lithium alloy (new generation). This behavior is being studied by conducting fatigue testing on a common lap joint design at three different specimens sizes, namely: (1) single rivet column coupons, (2) wide flat panel specimens, and (3) curved sub-scale panel specimens. Data from this study will be used to assess the relevance of existing regulations and to inform whether additional safety standards and regulatory guidance should be developed to provide improved safety beyond that afforded by the existing airworthiness standards. Additionally, results will be used to support potential improved weight and structural safety performance expectations of the EMST and to evaluate the effect of specimen scale on fatigue performance. As part of this program a subset of the 2524-T3 wide flat panels and curved sub-scaled panels were manufactured with an initial MSD scenario. The purpose of the MSD scenario was to establish a common starting point for the crack growth and residual strength portions of the tests in order to facilitate better posttest comparisons. Additionally, using finite element modeling it was anticipated that the wide flat panels would experience higher secondary bending of the joint compared to the curved sub-scaled panels. Therefore, a subset of the MSD wide flat panels were also tested with an anti-bend device that was designed to constrain the bending and bring it closer to the predicted curved panel behavior. This paper will provide a brief overview of this program with focus on the test and analysis of the wide flat panel with the initial MSD scenario.