PSI - Issue 10

A. Karanika et al. / Procedia Structural Integrity 10 (2018) 66–72 A. Karanika et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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optimization strategy. New structural design concepts and innovative materials can contribute to the weight reduction of aircraft structures. To this end, materials used in manufacturing airframe components need to become lighter, more resistant in cor rosion, cheaper and more eco-compliant. These components will include the composite wing, the metallic or composite fuselage and the cockpit structure. From an environmental and societal point of view, it will be necessary to reduce the aviation footprint, through aircraft performance improvements (drag, weight and versatility) and an eco-friendly life cycle including a significant decrease of hazardous materials during the manufacturing phase. ACARE targets and REACH regulations should be also fulfilled. Within the frame of all the above mentioned needs and targets, Hellenic Aerospace Industry (HAI) is participating in Clean Sky2: ecoTECH seven years core project (2016-2022). Surface treatments anticorrosive technologies are under development and evaluation in ecoTECH project:  New chromium free anodization surface treatments.  Sprayable out-of bath surface treatments. In the present work, the current activities are presented in terms of surface treatments, mechanical characterization and formability performance on new Al-Li alloys. The objective of this work was the investigation and characterization of high-strength aluminum-lithium (Al-Li) alloys with improved behavior regarding mechanical properties, formability and corrosion resistance. The investigated substrate materials are new Al-Li alloys (i) 2060-T8E30 by ARCONIC from ARCONIC and 2198-T3 by Constellium. So far, tensile and fatigue properties of 2060-T8E30 specimens have been characterized in L direction according to the specifications ASTM E8 and BS EN 6072, respectively. Sheets of the above-mentioned alloy have also been subjected in rolling and bending experiments for various radius to estimate the formability performance of the new alloys. New Al-Li alloys attain better-off behavior against corrosion, thus allowing for less severe corrosion protection schemes, e.g. Polmear et al. (2017). The objectives of this research activity are to investigate the effects of different surface treatments and anticorrosion paints on new aluminum components. The investigated surface treatments presented in this work are: (i) Thin Film Sulphuric Acid Anodizing (TFSAA) and (ii) sprayable application of Sol Gel treatment (AC131 from 3M TM ). Both treatments are fully Chromium free and REACH compliant. Prior to these treatments, the Al surfaces were given the surface preparation processing presented hereafter:  alkaline degreasing,  rinsing,  alkaline etching,  rinsing,  desmutting, and  final rinsing. Fig.1 shows several SEM images of the surface of AA2198 alloy after its surface preparation. After these steps, the surfaces were coated with either (i) or (ii) treatment and then the samples were subjected to Salt Spray corrosion Test (SST) according to the ASTM B117 specification. TFSAA was performed in an experimental, laboratory scale setup. Fig.2 shows the experimental setup as well as depicts the main TFSAA process parameters. During the anodization cycle, the current density and the electrolyte temperature was recorded. 2.2. Surface treatments 2. Experimental procedure 2.1. New aluminum – lithium alloys