Title: Innovative Sizing Method for Fastener-Free Thermoplastic Airframe

Authors: Mrs. Sandrine Meyer, Mr. Alexis Pierunek, Mr. Laurent Dubreuil.

DOI: 10.33599/nasampe/c.22.0015

Abstract: State-of-the-art composite long-range aircrafts are manufactured from thermoset materials with manufacturing processes that are known and proven. Recently developed high-performance thermoplastic composites can be melted and consolidated several times, which enables a fastener-free assembly (either by welding or co-consolidation) and the integration of functions through over-moulding.

Up to now, there is no certified method available to assess the performance of this new type of assembly. The assembly interface strength is depending on the materials to join, the joint design, the processes used to manufacture each adherents and the processes used to actually join the parts.

The “inter-laminar” failure, also known as delamination, is the main and the most critical damage mechanism in laminated composites. Mode I delamination (pull-out) is the most severe and sudden failure mode. In this document, the use-case studied is a Frame to Skin junction of a fuselage, highly loaded under pull-out load due to aircraft internal pressure.

In order to establish the elementary technological bricks, Airbus Atlantic has applied a novel approach. This methodology takes into account the failure micromechanics theory involving stored energy at the crack front to assess with accuracy the strength of frame to skin fastener-free thermoplastic junction based on experimental results.

This method relies on specific interface cohesive elements which are able to sustain stresses up to a defined threshold, and then are gradually damaged until total collapse of mechanical performance. The successive failures of interface elements simulate the crack propagation of a thermoplastic composite interface, up to complete de-cohesion.
In order to characterize the interface material properties, the methodology is based on the identification of the cohesive law parameters by correlation of coupons tests and then the evaluation of these properties on sub-component assembly i.e. skin to frame pull-out.

This study shall allow the assessment of the TP joint simulation method with cohesive FE and the comparison with the aircraft target loads. This new approach for sizing welded TP junction is a key enabler to establish optimized design of TP airframe with weight saving benefits.

References: [1] AITM Standard 1-0006, 1994, “Carbon Fibre Reinforced Plastics. Determination of interlaminar fracture toughness energy - Mode II” [2] AITM Standard 1-0069, 2011, “Fibre Reinforced Plastics. Determination of curved-beam failure load.” [3] AITM Standard 1-0005, 2015, “Carbon Fibre Reinforced Plastics. Determination of interlaminar fracture toughness energy - Mode I” [4] ASTM Standard D2344-00, 2006, “Standard test method for short beam strength of polymer matrix composite materials and their laminates” [5] ASTM Standard D6671-00, 2006, “Standard test method for short beam strength of polymer matrix composite materials and their laminates” [6] Beckelync, B., Thesis, “Etude de la délamination sur des matériaux composites tissés taffetas: Essais de caractérisation et simulations numériques”, 2016 [7] Bertolini, J., Thesis, “Contribution à l'analyse expérimentale et théorique des ruptures de structures composites en post-flambement par décollement de raidisseurs”, 2008 [8] Lachaud, F., Thesis, “Délaminage de matériaux composites à fibres de carbone et à matrices organiques: étude numérique et expérimentale, suivi par émission acoustique”, 1997 [9] Lecomte - Grosbras, P., Thesis, “Utilisation de la technique de corrélation d'images pour l'étude des effets de bord dans les composites stratifiés”, 2009 [10] Prombut, P., Thesis, “Caractérisation de la propagation de délaminage des stratifiés composites multidirectionnels”, 2007 [11] Gong, X., Hurez, A., Sun, H., Thesis, “Effet de l’orientation des fibres des plis adjacents sur la résistance au délaminage en mode I”, 2009

Conference: CAMX 2022

Publication Date: 2022/10/17

SKU: TP22-0000000015

Pages: 15

Price: $30.00