## 1 Introduction
In the end, it becomes evident that the tool will be in contact with a variety of fluids and environments from the time of its initial design until the conclusion of its life cycle (generally speaking, after six resharpening cycles), reinforcing the need for this study. Overall, the effects of high temperatures, corrosive environments and humidity have been long understood as detrimental to the long-term use of polymeric materials and require careful study [15]. In some way or another, all adhesives absorb water, and it is known that, for structural adhesives, the rate of water diffusion increases with temperature, following the Arrhenius equation [16; 17; 18]. The process of predicting the effects of fluid absorption and temperature on adhesives requires characterization of the diffusion methods within the joint. Sorption can be divided into two cases, diffusion-controlled and relaxation-controlled. If the diffusion rate is greater than the relaxation rate, it is called Fickian behaviour, and if the relaxation rate surpasses the diffusion in controlling the water uptake, it is known as non-Fickian behaviour [16; 19]. The use of [PERSON]'s law is suitable for Fickian processes, but for relaxation processes, a dual-Fickian model should be used instead. Structural epoxies may fall into this category. This model can approximate anomalous uptakes and take into account multiple equilibrium states in the sorption process. Various models exist under this category, but they are more numerically complex than [PERSON]'s law [16; 20]. Though there has been extensive published research to characterise the diffusion of water and its effects on polymeric materials, there has been limited research on the effects of common industrial fluids on the hygrothermal degradation of the adhesive connections. Similar research has been conducted for automotive applications, focusing on the effects of weather and motor oil. The findings of this research have been mixed, but generally indicate that the oils are less damaging to the adhesive than water [21]. Another concern that arises when one considers the production of adhesively bonded milling tools is the need for surface coatings, which in this case fulfil solely aesthetic purposes, but can also be instrumental to improve durability, minimising the effects of long-term corrosion. The main treatments used in steel tools are oxidation and nickel-plating, while anodization is used for aluminium tools. Both cases require long exposure to high-temperature chemical baths, which pose a threat to the strength of the bonded connections. Additionally, adhesives and adhesive joints are also quite susceptible to temperature. When heated to high temperatures, residual thermal stresses are created in bonded joints due to the mismatch of the adherends' and adhesive's coefficients of thermal expansion (CTE). Cooling the joint can also lead to high interfacial stresses between the substrate and the adhesive layer. This results in a damaged mechanical response, which is negatively impacted by thermal cycles, and can result in a low-to-moderate reduction in their average failure load and stiffness [22; 23]. Furthermore, [PERSON] et al. [24] have shown that the adhesives' poor resistance to high temperature, resulting from their polymeric nature, limits their use in many applications. Additionally, unrecoverable degradation will occur at higher temperatures, as the polymeric chains decompose. Thus, the repair process for damaged milling tool bits can negatively affect joint performance due to the application of heat to remove or cure the adhesive of the damaged bit, which exposes the adhesive of undamaged bits to multiple high-temperature cycles for each repair performed. The adhesive considered for this work is a one-part heat curing epoxy, previously characterised by [PERSON] et al.