Issue 45

C. Bellini et alii, Frattura ed Integrità Strutturale, 45(2018) 173-182; DOI: 10.3221/IGF-ESIS.45.15 181 Figure 9 : DSC results from EA 9309NA specimen aged in distilled water. C OMPARISON BETWEEN AF 163-2K AND EA 9309NA nalysing the results, it is evident that the ageing conditions have different effects on the two adhesives analyzed. In particular, the AF 163-2K shows greater stability in water than the EA 9309NA. Armstrong [6] noted that these two types of glue have different values of diffusion and solubility of the water inside them. In particular, the value of the product between the diffusion coefficient and solubility is about four times higher in the case of EA 9309NA concerning the value of AF 163-2K. In addition, the soak times observed by Armstrong [6] that are required to have a strong decrease in fracture energy are respectively 300 days in the case of AF 163-2K and 22 days in the case of EA 9309NA. It is possible to deduce that the green part of the failure surfaces of the specimens made with EA 9309NA has undergone a strong degradation, which is located on the edges of the bonding area since the times used for the ageing cycles have not been sufficient to allow water to penetrate to the bulk of the bonding area. Vice versa, the specimens made with AF 163- 2K did not deteriorate at the end of the ageing cycles since the thirty days used for the ageing cycles are not sufficient for the water to penetrate inside the adhesive, and therefore an appreciable degradation of joint strength cannot be observed. C ONCLUSIONS ingle lap bonded joints in the composite material were made with two types of adhesive: film (AF 163-2K) and paste (EA 9309NA). Subsequently, the specimens were subjected to ageing cycles in air, distilled water and salt water with temperatures between -28 ° C and 85 ° C, and then tested. Regarding the joints made with the AF 163-2K, ageing did not particularly affect the apparent shear strength. Concerning the specimens made with the EA 9309NA, ageing has played a greater role in the apparent shear strength of the joints. In particular an increase in the apparent resistance of the joint aged in air was observed, due in part to a post- cure effect of ageing on the adhesive; while in the case of joints aged in water the apparent resistance is directly proportional to the degradation of the adhesive. This has occurred because the degradation is more localized in the edges of the bonding area, which is where this type of specimen has a stress singularity: in this way, the adhesive has a lower resistance but a greater ductility where such properties are required. R EFERENCES [1] Sorrentino, L., Turchetta, S. and Bellini, C. (2017). Analysis of carbon fibre reinforced polymers milling by diamond electroplated tool. Diam. Relat. Mater. Elsevier. 76, pp. 184–90. DOI: 10.1016/j.diamond.2017.05.005. A S