Optimization of Adhesive Joint Design in Timber–Glass Systems: Enhancing Structural Performance with Primer Treatment
Abstract
:1. Introduction
2. Materials and Methods
- Adhesive Failure (AF): Failure occurring at the interface between the adhesive and the adherend when the resistance of the interface (adhesion strength) is less than that of the adherend.
- Cohesive Failure (CF): Failure occurring within the adhesive; therefore, the latter is present on both fracture surfaces.
- Thin-Layer Cohesive Failure (TLC): Cohesive failure occurring very close to the adhesive—substrate interface, characterized by a “light dusting” of the adhesive on one substrate surface and a thick layer of the adhesive left on the other.
- Timber-Tear Failure (TT): Failure occurring exclusively within the timber component, characterized by the presence of timber fibers on both ruptured surfaces.
- Light-Timber-Tear Failure (LTT): Timber failure characterized by a thin layer of timber fibers visible on the adhesive.
- Stock-Break Failure (SB): Breaking of the glass substrate outside the adhesively bonded joint region, often occurring near it.
- Mixed Failure (MF): Any combination of two or more of the previous classes of failure modes described.
3. FE Model
4. Results and Discussion
4.1. Experimental Results
4.2. Numerical Results and Experimental Data Comparison
5. Conclusions
- (1)
- The pre-treatments on the glass and/or timber side of the bonded joint reduce the maximum displacement, shear stress, and shear strain. They may also contribute to increase the maximum failure load of the joint, but this behavior is not observed for all the tested series; in particular, adhesion promoters (111 and 94) seem to have a better effect than a moisture inhibitor (Silane) in this respect. As a consequence of the decrease in the ultimate displacement, all pre-treated series have higher stiffness than the untreated ones. These treatments, in fact, improve surface adhesion at the adherend—adhesive interface, which in turn enhances load transmission between the adherents up to the maximum permissible stress of the glass, before the adhesive failure (AF) occurs. This aspect of stiffness is relevant according to the different fields of application (i.e., depending on the displacements that the joint can bear, a combination is more or less suitable for a specific purpose).
- (2)
- The behavior of the painted joint strongly depends on the type of paint used on the glass: a paint of the same nature of the adhesive (i.e., epoxy paint) can increase the ultimate load but has no significant effect on the remaining considered parameters (as summarized in Table 8), nor on the type of failure mechanisms. Conversely, the use of an acrylic paint causes a worsening of the overall mechanical behavior and shifts the collapse mode from glass failure to interface failure.
- (3)
- According to the results of the numerical modeling, it can be concluded that the simulation appears to be more representative of all those series where adhesive promoters are used. This aspect can be attributed to the fact that the usage of adhesive promoters reduces the effects on the joint structural behavior of the uncertainties affecting all specimens because of the manufacturing process, which cannot be easily included in the modeling.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Glass [32] | Beechwood [33] | |||||
---|---|---|---|---|---|---|
Thermal Coeff. of Expansion | Young Modulus | Tensile Strength | Density | Moisture Content | Young Modulus | Tensile Strength |
α (°C−1) | E (GPa) | σR (MPa) | ρ (kg/m3) | % | E (GPa) | σR (MPa) |
9 × 10−6 | 75 | 30 | 720 | 15 | 1.5 | 90 |
Chemical nature | two-part | toughened epoxy base + modified amine accelerator | |
Viscosity | - | thixotropic | |
Work life | Wl | (min) | 45 |
Application temperature | At | (°C) | 15 ÷ 30 |
Glass transition temperature | Tg | (°C) | 66.87 |
Service temperature | St | (°C) | −40 ÷ 80 |
Shear strength | τ | (MPa) | 6.2–24.3 * |
Young modulus in compression | Et | (MPa) | 3500–4000 |
Use | - | semi-structural |
Epoxy-Based | Acrylic-Based—Type A | Acrylic-Based—Type B | |
---|---|---|---|
Color | silver | black | black |
Type | 2-compound pearlescent paint for glass | bilayer is 100% solvent-based, high coverage | High Solids, solvent-based 2-component, satin finish |
Composition | 1 part paint + 0.6 diluent 1 + 0.45 catalyst 2 | 1 part paint + 0.5 diluent 3 | 1 part paint + 0.2 catalyst 4 |
Auxiliary components | 1 DT 810 Epoxy Thinner by Visa Colors 2 AM 85 Glossy Hardener | 3 disolvente acrìlico RU RAC medio | 4 Catalizador DCP9156, high adherence, by Racing colors (included with the paint) |
Silane | 111 | 94 | ||
---|---|---|---|---|
Main ingredient | (% by Weight) | isopropyl alcohol (80–95) * | propan-2-ol (98–100) | cyclohexane (30–60) * |
Boiling point | (°C) | 82.2 | 82.4 | 76.7 |
Flashpoint | (°C) | 11.7 | 11 | −17.2 |
Density | (g/mL) | 0.80 | 0.79 | 0.82 |
Vapor Pressure | (mmHg) | 43 (at 25 °C) | 330 (at 20 °C) | 68 (at 20 °C) |
Relative Vapor Density | 2.07 | 2.1 | no data available |
CTRL | Untreated |
SIL-G | Silane on the glass side |
111G | Primer 111 on the glass side |
SIL + 111G | Silane + Primer 111 on the glass side |
SIL-G_111T | Silane on the glass side and Primer 111 on the timber side |
111G-111T | Primer 111 on the glass side and Primer 111 on the timber side |
SIL + 111G_111T | Silane + Primer 111 on the glass side and Primer 111 on the timber side |
SIL-G_94T | Silane on the glass side and Primer 94 on the timber side |
111G_94T | Primer 111 on the glass side and Primer 94 on the timber side |
SIL + 111G_94T | Silane + Primer 111 on the glass side and Primer 94 on the timber side |
EPX | Glass treated with epoxy paint |
A | Glass treated with acrylic paint—type A |
B | Glass treated with acrylic paint—type B |
Longitudinal Young’s modulus | En | [MPa] | 4000 |
Transversal Young’s moduli | Es = Et | [MPa] | 1350 |
Nominal stress I mode | [MPa] | 42 | |
Nominal stress II mode | [MPa] | 15 | |
Nominal stress III mode | [MPa] | 15 | |
Critical fracture energy, mode I | Jm−2 | 380 | |
Critical fracture energy, mode II | Jm−2 | 190 | |
Critical fracture energy, mode III | Jm−2 | 190 |
Series | Specimen 1 | Specimen 2 | Specimen 3 | Specimen 4 | Specimen 5 |
---|---|---|---|---|---|
CTRL | SB + TLC (G) | SB | SB + AF (G) + CF + LTT | SB | SB + CF + LTT |
SIL-G | SB | SB + TT + TLC (T) | SB + LTT + TLC (T) | SB + TT | TT + LTT + TLC (T/G) |
111G | SB + TT + TLC (G) | SB + TLC (T/G) + LTT | SB + TT + TLC (G) | SB | SB + TT |
SIL + 111G | SB + LTT + TLC (T) | SB | SB | SB | SB + LTT + TLC (T) |
SIL-G_111T | SB | SB + TLC (T) + LTT+ AF (G) | CF + LTT + TLC (T/G) | SB | SB + TT + LTT + TLC (T) |
111G_111T | SB + TT | AF (G) + LTT + TLC (T) | SB + LTT + TLC (T) | SB | SB + TLC (T) + LTT |
SIL + 111G_111T | TT + LTT | SB + TT | SB + TT | LTT | SB + TLC (T) + LTT |
SIL-G_94T | SB | TLC (T) + LTT | SB + TT + TLC (T) | SB | SB + TLC (T) + LTT |
111G_94T | TLC (G) + LTT | SB + LTT + TLC (T) | SB + LTT + TLC (T) | SB + LTT + TLC (T) | SB + TT |
SIL + 111G_94T | SB + TLC (T) | SB + TT + LTT + TLC (T) | SB + LTT + TT + TLC (T) | SB + TLC (T) + LTT | SB + LTT + TLC (T) |
EPX | SB | SB | SB + CF + LTT + TLC (T) | SB + LTT + TLC (T) | SB + LTT + TLC (T) |
A | AF (G) + TLC (G) | AF (G) + TLC (G) | AF (G) | AF (G) | AF (G) |
B | TLC (G) + AF (G) | TLC (G) + SB + AF (G) | TLC (G) + AF (G) | TLC (G) + AF (G) | TLC (G) + AF (G) |
Series | Load max | Displ max | τmax | γmax | k | Failure Modes [39] |
---|---|---|---|---|---|---|
(kN) | (mm) | (MPa) | (-) | (kN/mm) | ||
CTRL | 8.90 ± 0.64 | 0.31 ± 0.05 | 7.26 ± 0.50 | 1.09 ± 0.16 | 30.39 ± 3.66 | 3 MF + 2 SB |
SIL-G | 8.61 ± 1.06 | 0.20 ± 0.05 | 6.67 ± 0.83 | 0.66 ± 0.16 | 44.62 ± 5.97 | 4 MF + 1 SB |
111G | 9.01 ± 0.73 | 0.18 ± 0.03 | 6.98 ± 0.57 | 0.62 ± 0.08 | 50.73 ± 5.97 | 4 MF + 1 SB |
SIL + 111G | 9.13 ± 1.47 | 0.18 ± 0.03 | 7.07 ± 1.14 | 0.63 ± 0.04 | 46.21 ± 10.89 | 3 SB + 2 MF |
SIL-G_111T | 9.18 ± 1.04 | 0.19 ± 0.03 | 7.11 ± 0.80 | 0.58 ± 0.09 | 49.88 ± 4.48 | 3 MF + 2 SB |
111G_111T | 9.20 ± 1.41 | 0.23 ± 0.07 | 7.13 ± 1.09 | 0.66 ± 0.21 | 43.19 ± 11.77 | 4 MF + 1 SB |
SIL + 111G_111T | 9.06 ± 0.82 | 0.17 ± 0.02 | 7.02 ± 0.64 | 0.53 ± 0.07 | 50.27 ± 3.02 | 4 MF + 1 LTT |
SIL-G_94T | 8.91 ± 0.87 | 0.18 ± 0.01 | 6.90 ± 0.67 | 0.60 ± 0.04 | 50.18 ± 6.09 | 3 MF + 2 SB |
111G_94T | 9.44 ± 0.65 | 0.20 ± 0.03 | 7.32 ± 0.50 | 0.68 ± 0.11 | 48.50 ± 4.85 | 5 MF |
SIL + 111G_94T | 8.59 ± 0.81 | 0.18 ± 0.03 | 6.66 ± 0.63 | 0.63 ± 0.10 | 48.46 ± 6.14 | 5 MF |
EPX | 10.10 ± 0.47 | 0.29 ± 0.04 | 7.82 ± 0.36 | 1.17 ± 0.30 | 34.87 ± 3.20 | 3 MF + 2 SB |
A | 2.72 ± 1.12 | 0.09 ± 0.03 | 2.11 ± 0.87 | 0.30 ± 0.12 | 30.06 ± 6.21 | 3 AF (G) + 2 MF |
B | 6.46 ± 0.72 | 0.21 ± 0.05 | 5.01 ± 0.55 | 0.70 ± 0.16 | 31.45 ± 4.75 | 5 MF |
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Agliata, R.; De Luca, A.; Caputo, F.; Marchione, F.; Sepe, R.; Munafò, P. Optimization of Adhesive Joint Design in Timber–Glass Systems: Enhancing Structural Performance with Primer Treatment. Appl. Sci. 2025, 15, 1616. https://doi.org/10.3390/app15031616
Agliata R, De Luca A, Caputo F, Marchione F, Sepe R, Munafò P. Optimization of Adhesive Joint Design in Timber–Glass Systems: Enhancing Structural Performance with Primer Treatment. Applied Sciences. 2025; 15(3):1616. https://doi.org/10.3390/app15031616
Chicago/Turabian StyleAgliata, Rosa, Alessandro De Luca, Francesco Caputo, Francesco Marchione, Raffaele Sepe, and Placido Munafò. 2025. "Optimization of Adhesive Joint Design in Timber–Glass Systems: Enhancing Structural Performance with Primer Treatment" Applied Sciences 15, no. 3: 1616. https://doi.org/10.3390/app15031616
APA StyleAgliata, R., De Luca, A., Caputo, F., Marchione, F., Sepe, R., & Munafò, P. (2025). Optimization of Adhesive Joint Design in Timber–Glass Systems: Enhancing Structural Performance with Primer Treatment. Applied Sciences, 15(3), 1616. https://doi.org/10.3390/app15031616