Issue 45

C. Bellini et alii, Frattura ed Integrità Strutturale, 45(2018) 173-182; DOI: 10.3221/IGF-ESIS.45.15 178 the influence of ageing simply considering a global ANOVA, but requires analysis of one-way variances by fixing the type of adhesive. AF 163-2K From a visual analysis of the results related to the joints made with the AF 163-2K adhesive (Tab. 4), it is possible to state that the resistance values are very close to the reference value regardless of ageing. Therefore the ageing cycles did not produce deleterious effects for this type of adhesive. The statistical variability observed for this type of adhesive is probably due to the autoclave process. In fact, this process may results in a misalignment able to affect the mechanical characteristics of the joint, but it does not influence the adhesive decay. The failure modes that show these specimens are all of the Light-Fibre-Tear type, according to ASTM D5573, as shown in Fig. 5. The high glass transition temperature of the adhesive probably gave greater stability to the maximum temperatures reached during ageing. Source Contribution Mean Square F-value P-value Ageing 39.56% 4.672 2.18 0.153 Error 60.44% 2.141 Total 100.00% Table 4 : One-Way ANOVA for AF 163-2K. a b c d Figure 5 : Failure surfaces of AF 163-2K specimens: a) without ageing; b) with air ageing; c) with distilled water ageing; d) with salt water ageing. EA 9309NA In the case of paste adhesive EA 9309NA (Fig. 4 and Tab. 5), it is possible to state that the behavior of the specimens has been heavily influenced by the ageing conditions, showing variable failure morphologies depending on the type of ageing. Joints aged in water undergo a strong increase in performance, achieving average performances of about 75% higher than the reference ones; also for samples aged in the air there is an increase in performance (due to a post-cure effect induced by the maximum temperature reached during ageing) but less significant (about 35%). Probably in this group of specimens, the effects of damage due to the thermal shock suffered during the transient from - 28 ° C to 85 ° C of the duration of few minutes have taken place, while the specimens aged in water have undergone a softer transient lasting about 2 hours. Furthermore, this difference between the two groups can be due to a greater ductility and lower mechanical resistance of the edges of the adhesive due to degradation in the water-aged specimens, which may have resulted in an increase of the