PSI - Issue 61

João C.M. Santos et al. / Procedia Structural Integrity 61 (2024) 79–88 Santos et al. / Structural Integrity Procedia 00 (2019) 000 – 000

82 4

2.2. Materials In addition to the main adhesive, three other adhesives were selected to evaluate the different adhesive joint geometries (Table 1). The Sika Adekit ® A 140-1 (Sika 2020) has excellent mechanical performance and resistance to dynamic loads (vibrations and impacts). To ensure ductility variation, the brittle epoxy Araldite ® AV138 (Neto et al. 2012), the moderately ductile epoxy Araldite ® 2015 (Campilho et al. 2012, Campilho et al. 2013), and the ductile polyurethane Sikaforce ® 7752 (Faneco et al. 2017) were also considered. Fig. 4 shows the correct stacking order for the deck adherend (left) and the hull adherend (right). Table 2 shows the properties of the materials that constitute the sandwich structure of a boat. The (A) carbon fiber (Haufler Composites 2017) and (B) glass fiber (Interglas Porcher Industries 2019) come in the form of fabric and the core of the kayak is (C) PVC foam (Diab Group 2021). To connect these materials, the matrix Resolcoat 1400-1407 epoxy resin was used (Résoltech 2023). The main elastic properties of the CFRP and GFRP laminate are listed in Table 3.

Table 1. Mechanical and fracture properties of the four adhesives.

Property

Adekit ® A 140-1

Araldite ® AV138

Araldite ® 2015

Sikaforce ® 7752 0.493±0.0896 3.24±0.5 11.49±0.3 19.18±1.4 5.16±1.1 10.17±0.6 58.42±6.4 2.36±0.2 5.41±0.5 0.187±0.0164 0.33 a

Young’s modulus, E [GPa] Poisson coefficient, v Tensile yield stress, σ y [MPa] Tensile strength, σ f [MPa] Tensile failure strain, ε f [%] Shear modulus, G [GPa] Shear yield stress, τ y [MPa] Shear strength, τ f [MPa] Shear failure strain, γ f [%] Tensile toughness, G Ic [N/mm] Shear toughness, G IIc [N/mm]

2.57

4.89±0.81

1.85±0.81

- -

0.35 a

0.33 a

36.49±2.47 39.45±3.18 1.21±0.10 1.56±0.01 25.1±0.33 30.2±0.40

12.3±0.61 21.63±1.61 4.77±0.15 0.56±0.21 14.6±1.3 17.9±1.8 43.9±3.4 0.43±0.02 4.7±0.34

30

4

0.99

-

20

-

7.8±0.7

0.5 5.56

0.2 0.38 b

b

a m anufacturer’s value ; b obtained in reference (Campilho et al. 2011)

Fig. 4. Stacking order for the deck adherend (left) and the hull adherend (right).

Table 2. Properties of the boat materials.

Property

(A) Carbon fiber

(B) Glass fiber

(C) PVC foam

Resolcoat 3100-3300

Young’s modulus, E [MPa] Yield stress, σ f [MPa] Fiber density, ρ [g/cm3] Area weight, G r [g/m2] Thickness, t [mm] Shear modulus, G [MPa] Poisson coefficient, ν Shear yield stress, τ f [MPa]

240000

33000

95 2.5

4200 1.78 160 0.30

626 2.6 220 0.25

-

0.08

1.15

-

- - -

3

-

-

27 0.4

0.27

0.33

0.35

-

-

1.15

-

Table 3. Elastic properties of the laminates.

Property E 1 [MPa] E 2 [MPa] G 12 [MPa]

CFRP 44028.7 4884.8 1809.9

GFRP 7854.8 4678.7 1734.1 0.343

0.322

ν 12