Issue 47

F. Moroni et alii, Frattura ed Integrità Strutturale, 47 (2019) 294-302; DOI: 10.3221/IGF-ESIS.47.22 294 Fracture and Structural Integrity: ten years of ‘Frattura ed Integrità Strutturale’ Comparison of tensile strength and fracture toughness under mode I and II loading of co-cured and co-bonded CFRP joints F. Moroni, A. Pirondi Dipartimento di Ingegneria e Architettura, Università di Parma, Parco Area delle Scienze, 181/A, 43124 Parma, Italy fabrizio.moroni@unipr.it, alessandro.pirondi@unipr.it C. Pernechele, A. Gaita, L. Vescovi Dallara Automobili, Via Provinciale, 33, 43040 Varano Melegari (PR), Italy c.pernechele@dallara.it, a.gaita@dallara.it, l.vescovi@dallara.it A BSTRACT . Carbon-Fiber Reinforced Polymer (CFRP) parts are joined mainly using adhesive bonding because, differently from fastening, additional parts (hence weight saving) and through holes (that are always detrimental for the strength due to the possibility of developing damage into the composite) are not necessary. Additionally, it allows for large connection areas, thus distributing stresses better than fastened connections. However, since CFRP can be joined by co-curing, the choice of bonding has to be evaluated as an alternative by a trade-off in terms of strength and durability, compared to cost and manufacturing time and complexity. In this work, a comparison between co-cured and co-bonded CFRP is done with respect to tensile strength and mode I and mode II fracture toughness, in order to understand whether co- bonding guarantees the same performance of a co-cured composite part. K EYWORDS . Carbon-Fiber Reinforced Polymer; bonded joints; fracture toughness. Citation: F. Moroni, A. Pirondi, C. Pernechele, A. Gaita, L. Vescovi Comparison of tensile strength and fracture toughness under mode I and II loading of co-cured and co-bonded CFRP joints, Frattura ed Integrità Strutturale, 47 (2019) 294-302. Received: 29.08.2018 Accepted: 17.10.2018 Published: 01.01.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he joining of composite laminates is alternatively made by mechanical fastening, bonding or co-curing, as testified from the large number of studies performed on the topic [1-7], while welding is confined to thermoplastic matrix composites. Fastening is preferred where decoupling for inspection and/or maintenance is necessary, but it requires the drilling of a hole through the composite that generates a fiber discontinuity, in turn affecting bearing and shear strength of the component. On the other hand, bolts and holes are not necessary when composite laminates are joined by bonding or co-curing, while the joint strength is typically limited by the onset of debonding or delamination. For this reason, the fracture toughness is a property of utmost importance to assess for the design of the connection, but it is also important to know it to compare different design solutions in terms of strength versus cost, manufacturing time and complexity. Four T