PSI - Issue 37

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Almudena Majano-Majano et al. / Procedia Structural Integrity 37 (2022) 492–499 Almudena Majano-Majano et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. Representative experimental G I - w I relationship with the fitted logistic function (left); cohesive laws of all specimens (right).

The mean parameters of the logistic function were used to build the mean cohesive law in mode I of eucalyptus bonded joints, which is highlighted in bold in Fig. 4 (right). This law could be implemented in numerical cohesive zone models to simulate the FPZ development and crack growth and thus analyse the actual fracture behaviour of the concerned bonded joint with these materials. 4. Conclusions A suitable methodology for a direct experimental identification of the cohesive law of Eucalyptus globulus L bonded joints in mode I was applied, which only requires the measurement of crack tip opening displacements ( w ) using the Digital Image Correlation (DIC) technique, and the evolution of the strain energy release rate ( G I ) during Double Cantilever Beam (DCB) tests. The Crack Based Beam Method (CBBM) based on an equivalent crack length, allows to determine the evolution of G I from the load-displacement curve, without the need to monitor the crack length during propagation, getting a mean G Ic value of 0.73 N/mm. Fitting a logistic function to G I = f ( w ) simplifies the derivation of the cohesive law. Therefore, the only limitation of this procedure is the fact that this type of fit establishes a shape for the law. The cohesive law could be accurately implemented in finite element models to predict the crack growth along a fracture process zone and to quantify the fracture behaviour of bonded joints made of this potential species in timber engineering. Acknowledgements This work has been developed during a short-term scientific stay by the first and second authors at the University of Trás-os-Montes e Alto Douro within the framework of the research project BIA 2015-64491-P Analysis of the stress relaxation in curved members and new joints solutions for timber Gridshells made out of Eucalyptus globulus , co financed by the Ministry of Economy and Competitiveness of Spain Government and ERDF funds. The authors acknowledge Fundação para a Ciência e a Tecnologia (FCT-MCTES) throughout the project UIDB/00667/2020 (UNIDEMI). References

Aicher, S., Christian, Z., Dill-Langer G., 2014. Hardwood glulams - Emerging timber products of superior mechanical properties. Proceedings of the World Conference on Timber Engineering, Quebec, Canada.