PSI - Issue 28

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ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Structural Integrity Procedia 00 (2019) 000–000 Procedia Structural Integrity 28 (2020) 917–924

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© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the European Structural Integrity Society (ESIS) ExCo Abstract Quasi-static tests were carried out on calibrated end loaded split (C-ELS) specimens to determine a critical initiation interface energy release rate or fracture toughness G ic . A multi-directional (MD) carbon fiber reinforced polymer (CFRP) laminate with a delamination between a unidirectional (UD) fabric ply with fibers oriented mainly in the 0 ◦ - direction and a plain balanced woven ply with tows oriented in the + 45 ◦ / − 45 ◦ - directions was considered. The G ic values from the non-precracked (NPC) specimens containing an artificial delamination were evaluated by means of an experimental compliance method (ECM), a beam theory (BT) method, as well as a two-dimensional finite element analysis (FEA) together with the area J -integral. In addition, the displacement extrapolation (DE) method and the virtual crack closure technique (VCCT) were used to determine the stress intensity factors K m ( m = 1 , 2) for each test. The stress intensity factors were normalized with a length scale ˆ L = 100 µ m and used to calculate the phase angle ˆ ψ . Finally, the obtained results were compared to critical initiation values which were obtained in a previous study from Brazilian disk (BD) tests for the same material and interface. The G ic value is a necessary property for predicting propagation of a delamination along the investigated interface. The aim of this paper is to examine the di ff erences which occur as a result of using various methods to determine this value. Work is in progress to determine fracture resistance curves or R -curves. These curves relate the energy required for a delamination to propagate G iR to the delamination extension ∆ a and may be used to predict the delamination resistance to propagation. c ⃝ 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) P r-revie under responsibility of 23 European Conference on Fracture - ECF23 . Keywords: delamination, energy release rate, fracture toughness, laminate composite, shear mode 1st Virtual European Conference on Fracture Comparison of methods for determination of fracture toughness in a multi-directional CFRP laminate Mor Mega 1 , Leslie Banks-Sills The Dreszer Fracture Mechanics Laboratory, School of Mechanical Engineering, Tel Aviv University, 6997801 Ramat Aviv, Israel Abstract Quasi-static tests were carried out on calibrated end loaded split (C-ELS) specimens to determine a critical initiation interface energy release rate or fracture toughness G ic . A multi-directional (MD) carbon fiber reinforced polymer (CFRP) laminate with a delamination between a unidirectional (UD) fabric ply with fibers oriented mainly in the 0 ◦ - direction and a plain balanced woven ply with tows oriented in the + 45 ◦ / − 45 ◦ - directions was considered. The G ic values from the non-precracked (NPC) specimens containing an artificial delamination were evaluated by means of an experimental compliance method (ECM), a beam theory (BT) method, as well as a two-dimensional finite element analysis (FEA) together with the area J -integral. In addition, the displacement extrapolation (DE) method and the virtual crack closure technique (VCCT) were used to determine the stress intensity factors K m ( m = 1 , 2) for each test. The stress intensity factors were normalized with a length scale ˆ L = 100 µ m and used to calculate the phase angle ˆ ψ . Finally, the obtained results were compared to critical initiation values which were obtained in a previous study from Brazilian disk (BD) tests for the same material and interface. The G ic value is a necessary property for predicting propagation of a delamination along the investigated interface. The aim of this paper is to examine the di ff erences which occur as a result of using various methods to determine this value. Work is in progress to determine fracture resistance curves or R -curves. These curves relate the energy required for a delamination to propagate G iR to the delamination extension ∆ a and may be used to predict the delamination resistance to propagation. c ⃝ 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 . Keywords: delamination, energy release rate, fracture toughness, laminate composite, shear mode 1st Virtual European Conference on Fracture Comparison of methods for determination of fracture toughness in a multi-directional CFRP laminate Mor Mega 1 , Leslie Banks-Sills The Dreszer Fracture Mechanics Laboratory, School of Mechanical Engineering, Tel Aviv University, 6997801 Ramat Aviv, Israel

1. Introduction 1. Introduction

As a result of their high strength and sti ff ness to weight ratio, CFRP composites have become desirable especially in the aerospace and marine structure industries [1]. However, such composites su ff er from low interlaminar sti ff ness which results in the formation of delaminations. In order to determine the interlaminar fracture toughness and improve As a result of their high strength and sti ff ness to weight ratio, CFRP composites have become desirable especially in the aerospace and marine structure industries [1]. However, such composites su ff er from low interlaminar sti ff ness which results in the formation of delaminations. In order to determine the interlaminar fracture toughness and improve

2452-3216 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the European Structural Integrity Society (ESIS) ExCo 10.1016/j.prostr.2020.11.064 1 Corresponding author. Tel.: + 972-3-640-8992 ; Fax: + 972-3-640-8992. E-mail address: pellegmor@gmail.com 2452-3216 c ⃝ 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 . 1 Corresponding author. Tel.: + 972-3-640-8992 ; Fax: + 972-3-640-8992. E-mail address: pellegmor@gmail.com 2452-3216 c ⃝ 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 .