PSI - Issue 18

ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 18 (2019) 719–730

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. Abstract The use of mechanical fasteners is still main assembling method for CFRP sub-structures in aircrafts and helicopters. However, this type of joint introduces complex stress field in the hole surroundings producing failures risk. In this work, a progressive damage 3D model of the riveted joint has been implemented to predict the residual strength and compliance after first damage signs and reproduce the final failure of composite joints under tensile test. Two 3D FEM Models were used and results are compared to experimental tests. The junction stiffness under load was evaluated and preliminary analysis shows both the coefficient of friction and preload induce not significant alteration of the composite joint behaviour. On refined model, a 3D Hashin-type failure criterion was used to analyze damage of matrix and fibers, beginning in the hole where contact conditions with the bolt pin and head are more severe and is evenly distributed in various plies, leading to final rupture of second or third one. Successively, delaminations were introduced with cohesive model, since is considered to produce reliable results, because the initial compression collapse in critical layers in contact with rivet is proved to affect shear and compression load transfer to other layers, giving rise to localized internal delaminations, propagating successively in width. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 25th International Conference on Fracture and Structural Integrity Damage investigation of Aeronautical CFRP laminates under Bearing Tests V. Dattoma a , R. Nobile a , F. W. Panella a , A. Pirinu a , A. Saponaro a * a Department of Engineering for Innovation, University of Salento, Lecce 73100, Italy Abstract The us mechanical fa teners is still main assembling method for CFRP sub-structures in aircrafts and helic pt r . However, this type of joint introduces complex stress fi ld i the hole surroundings produci failures risk. In this work, a progressive dam ge 3D model of the riveted joint has been implemented to predict the residual strength and compliance fter first d mage signs and re roduce the final failure of composite joints under tensile test. Two 3D FEM Models were used and r sults are compared to experimental tests. The ju ction stiffness u der load was evaluated and prelimi a y analysis shows both t e coefficient of fricti and preload induce not significant lteration of the composite joint be aviour. On refined mo el, a 3D Has in-type failure criterion was u d to alyz damage of matrix and fibers, beginning in the hole wh re contact conditions with th bolt pin and he d are mor severe an is evenly distributed in various plies, lea ing to final uptur of second or third one. Suc essively, delaminations were introduced with ohesive model, since is consider d to produce reliable results, because t initial compression collapse in critical layers i contact with rivet i proved to affect shear and compression load transfer to other layers, giving rise to localized internal delaminations, propagating successively in width. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 25th International Conference on Fracture and Structural Integrity Damage investigation of Aeronautical CFRP laminates under Bearing Tests V. Dattoma a , R. Nobile a , F. W. Panella a , A. Pirinu a , A. Saponaro a * a Department of Engineering for Innovation, University of Salento, Lecce 73100, Italy 1. Introduction Predicting the strength of single lap joints is of great practical importance, since inadequate design may result in aircraft structural anomalies, reducing load carrying capability of the components. The technology for optimum design of bolted composite joints is still evolving due to internal complex phenomena governed by many parameters. The relative simplicity of the majority of models used in literature to simulate behaviour of bolted composite joints is not 1. Introduction Predicting the strength of single lap joints is of great practical importance, since inadequate design may result in aircraft structural anomalies, reducing load carrying capability of the components. The technology for opti um design of bolted composite joints is still evolving due to internal complex phenomena governed by many parameters. The relative simplicity of the majority of models used in literature to simulate behaviour of bolted composite joints is not Keywords: CFRP; bolted joints; bearing failure; Cohesive Zone Modeling; FEM; Damage Evolution. Keywords: CFRP; bolted joints; bearing failure; Cohesive Zone Modeling; FEM; Damage Evolution.

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. * Andrea Saponaro. Tel.: +39 (0)832 297786; fax: +39 (0)832 297768 E-mail address: andrea.saponaro@unisalento.it * Andrea Saponaro. Tel.: +39 (0)832 297786; fax: +39 (0)832 297768 E-mail address: andrea.saponaro@unisalento.it

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 10.1016/j.prostr.2019.08.220