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1st Int. Transborder Conf. of the Timor Island: Timor %u2013 Science without borderDili, 7-8 May 2025179The Impact of Water Absorption On the Joint Strength of the AdhesiveJoviano A. da CostaDepartment of Mechanical Engineering, Faculty of Engineering Science and Technology, Universidade Nasional Timor Loro Sa%u2019e, Timor-LesteEmail: joviano.dacosta@untl.edu.tlAbstractThe impact of water absorption on adhesives and adhesive joints is a critical factor that must be considered in their applications. Adhesives inherently absorb moisture in humid environments; therefore, the effect of humidity on joint performance should be addressed during the design phase. This study aimed at evaluating moisture absorption in adhesive joints for continuous hygrothermal ageing. This ageing process was used to investigate how increasing water content in the adhesive layer affects joint strength. This study specifically examined the influence of hygrothermal ageing on the mode I joint strength of epoxy-based adhesive joints. Joint strength and surface failure were evaluated experimentally using Arcan joint specimens aged in controlled environments with varying humidity levels. The specimens were bonded using epoxy adhesive and aged for 2, 7, and 14 days in a chamber maintained at 50%u00b0C. Following ageing, the specimens were tested under mode I loading to determine the static strength. Results showed that joint strength decreased with increased ageing time. Additionally, failure surfaces transitioned to adhesive failure due to moisture ingress. Fatigue tests were also performed at different static load levels to determine the number of cycles to failure. These tests confirmed that fatigue life, like static strength, declined with increased water content in the adhesive layer. Humidity was found to be detrimental to bonding strength, causing interfacial failure. To simulate water ingress in Arcan joints, a finite element approach using Abaqus 2017 software was employed. The diffusion coefficient (D), obtained experimentally, was used to model moisture uptake in the adhesive layer. The water absorption depth was found to be a function of both the diffusion coefficient and ageing time. However, failure surface analysis indicated that water diffused more rapidly at the interface than within the adhesive layer, suggesting different diffusion coefficients for these regions. To resolve this discrepancy, an inverse method was used to recalibrate the diffusion coefficient for the interface, which was then applied in simulations to better predict water absorption behavior.Keywords: Adhesive joints, Arcan, ageing, static, fatigue life, interfacial failure.