PSI - Issue 47

11

Francesco Ascione et al. / Procedia Structural Integrity 47 (2023) 826–841 Author name / Structural Integrity Procedia 00 (2019) 000–000

836

Fig. 11. Numerical P- δ curves: influence of � ( � = 20 MPa, �� , � =0.55 N/mm).

3.4 P- δ curves: a comparison between numerical and experimental investigation

In this sub-section a comparison between the numerical and experimental results, in terms of P- δ curves, are presented and discussed. In detail, the comparison is referred, for each epoxy resin under investigation, to the unaged and aged ultimate condition (15 months for SikaDur 30 and 12 months for Araldite). Relating to the unaged and aged condition, the following values for the governing parameters were considered to perform the numerical simulations (Table 4).

Table 4. Values of the governing parameters for unaged and aged conditions. SikaDur 30

Araldite AV 5308 �� , � � � �� , � � [MPa] [MPa] [N/mm] [MPa]

�

[N/mm]

[MPa] 24000

Unaged

0.58 0.69 0.81

17 17 17

24000 24000 24000

4.11 3.28 0.92 4,39 4,74

9

Aged SW,A Aged TW,A Aged SW,D Aged TW,D

7 (22%) 7 (22%)

12000 (50%) 12000 (50%)

- -

- -

- -

9 9

24000

24000 A= absorption, D= desorption, in () the reduction in percentage with respect to the unaged condition

The values of the limit shear stress for the unaged condition are those declared by the suppliers [32,33] for a curing at the temperature of 23±2°C. Finally, the value of Young Moduli of the GFRP adherents for the unaged condition is the one proposed by the supplier. Regarding the values of the governing parameters referring to the aged conditions with absorption only, the following consideration are useful: - for SikaDur 30, due to the aging conditioning, the value of the maximum load increased (increment of �� , � � ), without significant changes in terms of stiffness ( � ) of the P- δ curves and changes in terms of shape ( � ), which remains elastic-brittle; - for Araldite AV 5308, due to the aging conditioning the value of maximum load decreased (decrement of �� , � � ), the shape of P- δ curves changed from ductile to elastic (decrement of � ) and the stiffness of P- δ curves decreased (decrement of � ).