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Analysis of water absorption on the efficiency of bonded composite repair of aluminum alloy panels

  • Faraz Ahmed , Rachid Mhamdia , Sohail M. A. K. Mohammed , Faycal Benyahia , Abdulmohsen Albedah EMAIL logo and Bel Abbes Bachir Bouiadjra
Published/Copyright: February 1, 2024
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Science and Engineering of Composite Materials
From the journal Science and Engineering of Composite Materials Volume 31 Issue 1

Abstract

Carbon fiber-reinforced polymer (CFRP) exhibits aging effects over time that can degrade its mechanical properties. In this study, a systematic investigation was carried out to investigate the effect of distilled water aging on the mechanical properties of CFRP composite patch bonded on Al 2024-T3 plates. We built a finite element model to analyze the effect of water absorption by the composite and the adhesive on the effectiveness of the composite patch repair. Using the experimentally evaluated mechanical properties of CFRP and Araldite adhesive subjected to distilled water immersion, finite element simulations were validated. The experimental observations deduce that there was a negligible effect of moisture absorption on the bulk mechanical properties of CFRP and adhesive over time. However, a significant effect of moisture absorption was observed on the elasto-plastic behavior of both CFRP and adhesive. Consequently, the numerical simulations suggest that the moisture absorption reduces the bonded composite patch repair efficiency attributed to an increase in the plasticity around the crack front and accordingly increases the damage in the adhesive layer. This study attempts to provide guidelines on the severity of damage caused by water absorption on the performance of structures repaired with composite patches.

Keywords: bonded composite repair; aluminum alloy; stress intensity factor; plastic zone; adhesive damage; CFRP

1 Introduction

Fiber-reinforced composites are widely accepted for bonded composite repair of the damaged structures particularly in the aerospace, transportation, construction, marine applications, etc. In metallic structures, the cyclic fatigue stresses generally lead to the crack initiation at high stress concentration sites [1,2]. Such cracks can be repaired using composite materials such as high strength, lightweight carbon fiber-reinforced polymers (CFRPs) as patches. Consequently, the stress intensity around the crack front is reduced, resulting in increased fatigue life of the repaired structures [3,4,5,6,7]. However, the major problem with composites is their aging over time, which makes the prediction of service life for these materials quite difficult [8,9]. This aging can be caused by several parameters, including moisture absorption, exposure to ultraviolet light, and temperature effects [10,11,12]. The combined effects of the aging parameters lead to the deterioration of the mechanical properties of the composite material, and consequently, the repair performance will be reduced [12,13,14]. Natural aging usually takes a very long time to affect the mechanical strength of the composite material, so it is imperative to use accelerated aging in order to have a prediction of the behavior over relatively short times that could be representative of the natural aging of the composite [15,16].

The adhesives used in the repair techniques of metal structures by composite materials are usually fabricated using thermoset polymer resins. These resins are also the matrices for composite patches. Adhesives are also sensitive to the external environment, particularly moisture absorption and temperature variation [17]. It has been shown that moisture absorption has a detrimental effect on the mechanical behavior of adhesive joints but predicting the durability of adhesive joints in damp or wet environments is a rather difficult task. Researchers have attempted to establish the relationship between loss of mechanical strength with water absorption rate and time in the adhesive joints [18,19,20,21,22]. Since the degradation of a joint takes a very long time to cause a significant loss of strength, multiple aging processes have been tried to accelerate the mechanical deterioration of adhesive joints. The processes of accelerated aging of adhesives involve increasing the relative humidity, increasing the temperature, and accelerating the diffusion of moisture into the adhesive layer by drilling holes in the center of the adhesive layer [23,24]. The diffusion of water along an adhesive joint is essential for predicting the degradation of the joint. Generally, Fick’s law can describe the diffusion of moisture into the body of an adhesive joint quite accurately, but diffusion into the interfaces and swelling problems can directly affect the rate of moisture absorbed by the adhesive layer until saturation. Nakamura et al. [25] showed that moisture diffusion is higher at the interface than in the adhesive body and that the effect of moisture is more sensitive at the interface. Using the relationship between Young’s modulus and water concentration in an adhesive joint, Wylde and Spelt [26] showed that moisture diffusion is higher than that predicted by Fickian diffusion, which allowed them to conclude that diffusion at the interface is a possible phenomenon. It has been shown by Oudad et al. [27] that the strength of the adhesive is significantly reduced by water absorption. The authors reported that the performance of composite patch repair of a cracked aircraft structure is negatively affected by water diffusion in the adhesive layer. Rezgani et al. [28] studied the effect of water absorption by the composite on the evolution of the stress intensity factor (SIF) at the head of a repaired crack in aluminum alloys. These authors found that the SIF decreases by about 70% in a repaired structure without moisture absorption, while the reduction in SIF is 46% when the moisture absorption rate is 1.46%. The problem of adhesive debonding during the composite patch repair process of damaged metal structures is a major handicap to the effectiveness and durability of the repair [29]. This problem can be aggravated by the aging of the composite and the adhesive. Indeed, the degradation of the mechanical properties of the composite patch and the adhesive leads to an increase in the risk of delamination of the adhesive layer, thus leading to a reduction in the lifetime of the repair.

The purpose of this study is to analyze the synergistic effects of aging of the composite patch and the adhesive by water absorption on the effectiveness and durability of the repair of a cracked Al 2024-T3 plate by bonding a CFRP patch. The study will be carried out numerically by the finite element method. Beforehand, experimental tests will be performed to measure the elastic properties of the composite and the adhesive after immersion in distilled water.

2 Experimental setup

The purpose of the experimental part of this study is to evaluate the mechanical properties of the CFRP and Araldite 2012 epoxy adhesive subjected to hygrothermal aging. The properties obtained experimentally are used as input for the numerical simulations of Al 2024-T3 repaired by bonding CFRP patch.

2.1 Tensile test on CFRP plate

Eight layers of prepregs, which contain about 65% by volume of carbon fibers, were cured in unidirection to prepare the CFRP plates. CFRP is manufactured by assembling the prepregs layers and curing them under pressure of about 6 MPa and temperature of 120°C for 90 min on hot press. To absorb the additional resin that comes out during curing, the prepregs must be sandwiched between woven fabrics of thermoplastic polymers. The tensile test specimens were machined from the cured CFRP plates. The composite plate, which is about 300 × 300 mm, is manufactured and cut into the desired shape (250 × 25 mm) using computer numerical control machine in accordance with the American society for testing and materials (ASTM) D3039 standard system, as shown in Figure 1. To study the effect of water absorption on the elastic properties of composites, the tensile specimens were immersed in distilled water for periods of 7, 98, and 147 days. The tensile tests were performed in the longitudinal (parallel to the direction of the fibers) and transverse (perpendicular to the direction of the fibers) directions.

Figure 1 Geometry of the composite tensile test specimen.
Figure 1

Geometry of the composite tensile test specimen.

2.2 Tensile test on adhesive specimen

The adhesive used in this study is Araldite 2012, which is an epoxy resin supplied as a bicomponent. The dog-bone tensile specimens were machined by curing the adhesive in the mold with the dimensions according to ASTM D5093 standard. The desired number of specimens were immersed in distilled water for durations of 7, 98, 125 and 147 days. Tensile tests were performed on aged and unaged specimens at a crosshead speed of 3 mm/min.

3 Numerical model

We used the three-dimensional finite element method with the Ansys code to evaluate the effect of the composite and the adhesive aging on the efficiency and the durability of the bonded composite repair. The repair efficiency was evaluated by calculating the SIF (K I) as elastic analysis, whereas the extent of the plastic zone is calculated as elasto-plastic analysis. The repair durability was evaluated by the estimation of the adhesive damage. The damage zone theory [30] was used for estimating the adhesive damage.

3.1 Numerical model of the repaired cracked plate

The geometrical model used in the numerical part is presented in Figure 2. The geometry of the model follows the experimental setup, which consists of an aluminum plate (2024-T3) with a lateral V-notch. A rectangular CFRP patch was bonded on the cracked Al 2024-T3 plate, covering the full width. The patch was bonded using Araldite 2012 adhesive. The dimensions of the aluminum plate are 100 × 50 × 2 mm with a V-notch with height and base of 6 mm, and the angle is 60°. The dimensions of the patch are 50 × 50 × 1.5 mm. The thickness of the adhesive was estimated to be 0.15 mm. The aluminum alloy and the adhesive are considered as elasto-plastic, whereas the carbon epoxy is considered as orthotopically elastic. The stress–strain curve of the aluminum alloy is given in Figure 3, and the elastic properties of the investigated materials in the as-received condition are presented in Table 1. The plate is subjected to uniaxial tensile loading with an applied stress of 70 MPa.

Figure 2 Geometrical model of repaired plate with bonded composite patch.
Figure 2

Geometrical model of repaired plate with bonded composite patch.

Figure 3 Stress–strain curve of the Al 2024-T3.
Figure 3

Stress–strain curve of the Al 2024-T3.

Table 1

Elastic properties of materials investigated in as-received conditions

Properties Al 2024-T3 CFRP Adhesive (Araldite 2012)
Longitudinal Young’s modulus (GPa) 72.4 185 2.9
Transversal Young’s modulus (GPa) 72.4 55.5 2.9
Longitudinal Poisson ratio 0.33 0.33 0.35
Transversal Poisson ratio 0.33 0.03 0.35

The Ansys computational code was used to achieve the main objective of this study. The finite element model consists of three sub-layers that, respectively, model the cracked plate, the adhesive, and the composite patch. The plate, the adhesive, and the composite are meshed separately with 20-node brick elements with exactly the same mesh on the contact surfaces. In order to have an accurate calculation at the crack front, we have refined the mesh around this front. The number of elements used in this study is 17,028: 12,216 elements in the aluminum plate, 3,208 elements for the composite patch, and 1,604 elements for the adhesive layer. Figure 4 shows the element model for the overall structure and at the crack region. To consider the material nonlinearity in the finite element model, we used the von Mises criterion associated with the theory of incremental plasticity. The nonlinear finite element equations were solved using the Newton-Raphson iterative method with a limiting number of steps of 100 and an increment size between 10 and 5 and 1, and the J integral along the curved front of the crack was calculated using the integral domain approach.

Figure 4 Typical mesh model of the assembly and near the crack tip.
Figure 4

Typical mesh model of the assembly and near the crack tip.

3.2 Damage zone theory description

The main assumption of the damaged zone theory is that failure of bonded joints occurs after the damaged zone develops. Under low loads, the damage localizes in the free edges because the material is locally stressed above the ultimate stress of the material. Under medium loads, the damaged areas will grow in size, and as the load at failure is reached, the damage area will grow to a critical size giving rise to joint failure. A failure criterion is applied to identify the critical area when it exceeds a certain threshold. The adhesive used in the analysis is a ductile adhesive that is expected to undergo ultimate loads. Therefore, the criterion used for a failure of the adhesive layer is of cohesive type, and it is equivalent to the von Mises criterion.

This criterion is satisfied when the maximum principal strain in the material reaches the ultimate principal strain. The damaged zone corresponds to the points in the adhesive layer where the ultimate strain is exceeded. For the Araldite 2012 adhesive, the damaged zone was defined as an area in which the strains exceed the ultimate strain, which varies with the immersion time in the distilled water.

We can also predict the damage of the adhesive joints by calculating the ratio of the damaged area, which is defined as follows:

(1) D R = ∑ A i l · W ,

where D R is the damage zone ratio, A i is the area over which the equivalent strain is greater than the ultimate strain, and l and W are the length and width of the adhesive layer, respectively. It has been reported that the adhesives peel off completely once the D R value reaches 0.2474 [30].

4 Results and discussion

4.1 Experimental results

4.1.1 Composite properties after aging

Tensile tests were conducted on unidirectional CFRP specimens in the longitudinal direction (along the fiber direction) and in the transverse direction (perpendicular to the fiber direction). These tests allowed us to measure the longitudinal and transverse moduli of elasticity of the composite as a function of immersion time in distilled water. The variations of the longitudinal Young’s modulus (E L) of the CFRP as a function of the immersion time in distilled water are presented in Table 2. We note a significant reduction in the modulus values as a function of the immersion time, similar to reported in the literature [31]. Indeed, the relative decrease of the modulus of elasticity is about 9% after 7 days of immersion. This decrease is about 21% after an immersion time of 98 days and 25% after an immersion time of 147 days. It is important to note that between the immersion times of 98 and 147 days, the reduction of the modulus of elasticity is only 4%. This is mainly due to saturation in water absorption after a long immersion period.

Table 2

Young’s modulus of the CFRP with respect to immersion time

Time of immersion in DW (days) Longitudinal Young’s modulus (GPa) Transversal Young’s modulus (GPa)
0 185 55.5
7 169 54.2
98 147 50.3
147 138 48.7

Table 2 presents the variation of the transverse Young’s modulus (E T) of the unidirectional composite as a function of immersion time in distilled water. After 7 days of immersion, the relative reduction of the transverse modulus by water absorption is about 3%, while for the immersion times of 98 and 147 days, it is about 10 and 12.3%, respectively. It can therefore be clearly deduced that the effect of water absorption on the transverse Young’s modulus is less consistent when compared to its effect on the longitudinal modulus.

The rate of water absorption of the composite or the adhesive can be estimated by measuring the weight gain t of each specimen defined by:

(2) M t = W t − W 0 W 0 × 100 ,

where M t is the weight gain percent at time t, W 0 is the initial weight of specimen, and W t is the weight of specimen after aging in distilled water for time t. For the carbon/epoxy, Zuhang et al. [32] showed that after 147 days of immersion in distilled water, the weight gain does not exceed 0.4%. This rate explains the weak effect of water absorption on the mechanical properties of the carbon/epoxy.

4.1.2 Adhesive properties after aging

Tensile tests on Araldite 2012 epoxy specimens after immersion in distilled water for the same times were performed: 0, 7, 98, and 147 days. These tests allowed us to plot the stress–strain curves of the adhesive with respect to immersion time (Figure 5). It can be clearly seen in Figure 5 that water absorption significantly affects the mechanical behavior of the adhesive. Indeed, the nature of adhesive changes from a thermosetting polymer to a perfectly plastic polymer behavior beyond the immersion time of 98 days. It is noteworthy that all mechanical properties were influenced by water absorption. For the ultimate deformation, it increases from 2% for an unaged adhesive to 7.5% after 98 days of immersion and to 6.3% after 147 days of immersion. Water absorption makes the adhesive very plastic, which will result in a considerable reduction in its ability to bond the two adhesives. Also, from Figure 5, it can be seen that the mechanical strength of the adhesive is negatively affected by water absorption. The ultimate stress of the adhesive is reduced from 28 MPa (unaged adhesive) to 22.5 MPa after 7  days of immersion, which gives a reduction of 14%. After an immersion time of 98 days, the ultimate stress was obtained to be 10 MPa; the reduction rate is about 65%. It can be seen from Figure 5 that the stress–strain curves of the adhesive after 98 days and 147 days of immersion are almost identical, which confirms that after a long period of immersion, we have a saturation in the absorption of water and the effects of this absorption on the mechanical behavior of the adhesive stabilizes after saturation [33].

Figure 5 Stress–strain curves of the adhesive for different time of immersion.
Figure 5

Stress–strain curves of the adhesive for different time of immersion.

The variation of the elastic modulus of the adhesive as a function of the immersion time is given in Table 3. The elastic stiffness of the adhesive is reduced by water absorption. The rate of reduction of this stiffness is about 5% after 7 days of immersion, and this rate increases to 59% after 98 days of immersion and 64% after 144 days of immersion. This reduction can be generalized to all the elastic properties of the adhesive, especially its shear modulus, which will also be significantly reduced after moisture absorption. The properties of the composite and the adhesive after immersion in distilled water will be introduced into the numerical model of the aluminum plate repaired by composite patch in order to estimate the effect of this immersion on the effectiveness of the repair.

Table 3

Young modulus of the Araldite epoxy adhesive for different time of immersion

Time of immersion in DW (days) Young’s modulus of the adhesive (GPa)
0 2.90
7 2.75
98 1.20
147 1.03

For the weight gain of the adhesive, the initial weight and the weight after water absorption were measured, then the weight gain was calculated using equation (2), and the results are shown in Table 4. It can be seen from this table that water absorption by the adhesive is very significant, even after 7 days of immersion, with an absorption rate of 11.1%. After 147 days of immersion, this rate increased to 21.4%. Water absorption by the adhesive is therefore very significant, leading to a degradation of the adhesive’s mechanical properties.

Table 4

Weight gain of the Araldite epoxy adhesive after different time of immersion

Time of immersion in DW (days) M t (%)
0 0
7 11.1
98 19.8
147 21.4

4.2 Numerical results

In the numerical study, we performed two types of analysis: a linear elastic analysis and a non-linear elasto-plastic analysis. In the elastic analysis, we assumed the elastic behavior for all three materials (aluminum, composite, and adhesive). Hence, the SIF at the crack tip was calculated using the energy release rate approach. The calculation of this factor was used to estimate the effectiveness of the repair after water absorption by the composite and the adhesive. In the elasto-plastic analysis, a non-linear behavior for the adhesive and Al 2024-T3 alloy was considered, and the repair efficiency was evaluated by calculating the extent of the plastic zone around the crack tip. Adhesive damage was also evaluated to observe the effect of moisture absorption on the durability of the composite patch repair.

4.2.1 Elastic analysis

Figure 6(a) shows the variation of the SIF as a function of the crack length for different immersion times in distilled water at the crack tip covered by the composite patch (repaired tip). It can be seen that the effect of water absorption on the variation in SIF is almost negligible when the crack length is less than 25 mm. This effect becomes sensible beyond a crack size of 25 mm. For an immersion time of 7 days, the effect of water absorption on the variation of the SIF is almost negligible since the curve of variation of the SIF for this immersion time practically overlaps with that of unaged patch (0 days of immersion). It can also be seen from Figure 6(a) that the critical SIF of about 42 MPa-m1/2 is reached only after a crack length of 35 mm, which shows that the patch can give a significant fatigue life to the repaired metallic structure.

Figure 6 SIF at the crack tip as a function of immersion time at (a) patched face and (b) unpatched face.
Figure 6

SIF at the crack tip as a function of immersion time at (a) patched face and (b) unpatched face.

Figure 6(b) shows the variation of the SIF as a function of the crack length as a function of immersion time at the unrepaired face of the plate. It can be seen that the behavior is similar to the one observed in Figure 6(a) (repaired face) except that in this case, the SIF values are higher (Figure 7). The critical SIF is reached from a crack length of 20 mm. It can be concluded that the elastic analysis showed a weak effect of water absorption on the variation of the SIF and consequently on the effectiveness of the repair. This observation obliged us to carry out the study with an elasto-plastic behavior, which is closer to the real behavior of materials.

Figure 7 Comparison between the values of the SIF for patched and unpatched crack tips (98 days of immersion).
Figure 7

Comparison between the values of the SIF for patched and unpatched crack tips (98 days of immersion).

4.2.2 Elasto-plastic analysis

The elasto-plastic analysis focuses on the evolution of plasticity around the repaired crack front after different immersion times in distilled water and the estimation of the effect of this absorption on the damage rate of the adhesive layer.

4.2.2.1 Extent of the plastic zone

Figure 8 shows the contour of the plastic zone around the crack tip on the unrepaired face of the Al plate for different immersion times, and the contour of the plastic zone was plotted for a crack length of 3 mm. We note from Figure 8 that the effect of water immersion on plasticity is quite noticeable and this effect increases with increasing crack size. The increase in plasticity with immersion time shows that the absorption of moisture significantly reduces the stress transfer from the Al plate to the composite patch through the adhesive layer causing the reduction of the repair efficiency. The contour of the plastic area increases by about eight times between an unaged patch and a patch immersed in water for 147 days, i.e., the repair performance can be reduced with the same rate.

Figure 8 Extent of the plastic zone for different times of immersion around the patched tip of the crack.
Figure 8

Extent of the plastic zone for different times of immersion around the patched tip of the crack.

The contour of the plastic zone in the unrepaired face of Al plate for a crack length of 3 mm and for different immersion times is shown in Figure 9. The behavior is similar to that observed in the earlier results (Figure 8). The absorption of water by the composite and the adhesive considerably increases the extent of the plastic zone around the crack, leading to a reduction in the effectiveness of the repair. On this unrepaired side, the relative increase in the size of the plastic zone between an unrepaired plate and a repaired plate after immersion in water for 147 days is four times. It should also be noted that between the two faces of the Al plate (repaired and unrepaired faces), the difference in the size of the plastic zone is very significant. Figure 10 shows a comparison of the evolution of the plastic zone radius between the repaired and unrepaired face of the Al plate for an immersion time of 98 days. It can be clearly seen that the difference in plastic zone radii between the two faces of the plate remains almost stable as the crack size increases.

Figure 9 Extent of the plastic zone for different times of immersion around the un-patched tip of the crack.
Figure 9

Extent of the plastic zone for different times of immersion around the un-patched tip of the crack.

Figure 10 Comparison between the values of the plastic zone radius for patched and unpatched crack tips (98 days of immersion).
Figure 10

Comparison between the values of the plastic zone radius for patched and unpatched crack tips (98 days of immersion).

4.2.2.2 Analysis of the adhesive damage

The use of the damaged zone theory allowed us to determine all the points in the adhesive layer that underwent a strain greater than the ultimate one. By gathering all these points, we were able to determine the damaged zone in the adhesive layer for different immersion times in distilled water. Figure 11 shows the extent of the damaged areas in the adhesive layer (in gray color) for a crack length of 3 mm and for different immersion times. It can be seen that the damage in the adhesive layer for this crack length is mainly localized in the cracked region. This is due to the high stresses in this region. The size of the damaged area increases with increasing immersion time. However, the effect of the immersion time is not noticeable between 0 and 7 days (Figure 11a and b). For immersion times of 98 and 147 days, the size of the damaged area in the adhesive layer is larger than in the case of the adhesive not immersed in distilled water (Figure 11c and d).

Figure 11 Damaged zones of the adhesive for different times of immersion for a = 3 mm: (a) non-aged, (b) aged 7 days, (c) aged 98 days, and (d) aged 147 days.
Figure 11

Damaged zones of the adhesive for different times of immersion for a = 3 mm: (a) non-aged, (b) aged 7 days, (c) aged 98 days, and (d) aged 147 days.

The damaged areas in the adhesive layer for a crack length of 40 mm and for different immersion times are shown in Figure 12. It can be seen that the damage to the adhesive has propagated to the free edges of the adhesive layer. The high stress intensity for this crack length (40 mm) caused an increase in the stresses transferred to the adhesive layer, which necessarily leads to more damage. The effect of water absorption on the damage for this crack length is more pronounced. It can therefore be stated that for fairly large crack sizes, water absorption will inevitably lead to a complete failure of the adhesion, and thus, the durability and effectiveness of the repair will be greatly weakened.

Figure 12 Damaged zones of the adhesive for different times of immersion for a = 40 mm: (a) non-aged, (b) aged 7 days, (c) aged 98 days, and (d) aged 147 days.
Figure 12

Damaged zones of the adhesive for different times of immersion for a = 40 mm: (a) non-aged, (b) aged 7 days, (c) aged 98 days, and (d) aged 147 days.

The results of Figure 13 confirm those of the earlier results. In this figure, the variation of the damage zone area ratio (D R) of the adhesive layer as a function of the immersion time for a crack length of 20 mm was shown. We note that whatever the immersion time, the critical ratio of 0.242 is exceeded (even for the case of non-immersed plate). This rate increases with the water absorption rate. This confirms that water absorption negatively affects the performance of the repair.

Figure 13 Damage zone ratio vs immersion time for a = 20 mm.
Figure 13

Damage zone ratio vs immersion time for a = 20 mm.

5 Conclusion

In summary, this systematic investigation delved into the implications of distilled water aging on the mechanical properties of CFRP-bonded Al 2024-T3 plates. The utilization of a finite element model enabled us to meticulously highlight the influence of water absorption by both the composite and adhesive materials, critically evaluating the bonded composite repair efficiency. The results obtained in this study show that the absorption of water by the CFRP patch slightly affects the elastic properties of this composite. On the one hand, this absorption has a considerable effect on the mechanical properties of Araldite 2012 epoxy adhesive. The stiffness and mechanical strength of this adhesive drop significantly after the absorption of moisture, especially for longer periods of absorption. Elastic analysis behavior of the repair patch after water absorption by the composite and the adhesive showed that this absorption has a slight influence on the variation of the SIF at the crack tip. However, the elasto-plastic analysis showed that the effect of water absorption is more pronounced, and it significantly reduces the stress transfer from the repaired patch to the composite through the adhesive layer. The damage to the adhesive increases quite significantly as the rate of water immersion increases. This study will be followed by an analysis of the fatigue behavior after water absorption by the patch repair.

  1. Funding information: This project was supported by the NSTIP Strategic Technologies Program, Grant Number (13-ADV2167-02), Kingdom of Saudi Arabia.

  2. Conflict of interest: Authors state no conflict of interest.

  3. Data availability statement: The data generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Received: 2023-04-24
Revised: 2023-12-02
Accepted: 2024-01-04
Published Online: 2024-02-01

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/secm-2022-0235
Keywords for this article
bonded composite repair; aluminum alloy; stress intensity factor; plastic zone; adhesive damage; CFRP
Creative Commons
BY 4.0

Articles in the same Issue

  1. Regular Articles
  2. Research on damage evolution mechanisms under compressive and tensile tests of plain weave SiCf/SiC composites using in situ X-ray CT
  3. Structural optimization of trays in bolt support systems
  4. Continuum percolation of the realistic nonuniform ITZs in 3D polyphase concrete systems involving the aggregate shape and size differentiation
  5. Multiscale water diffusivity prediction of plain woven composites considering void defects
  6. The application of epoxy resin polymers by laser induction technologies
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  27. Experimental analysis of frost resistance and failure models in engineered cementitious composites with the integration of Yellow River sand
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  29. Microstructure and finite element analysis of Mo2C-diamond/Cu composites by spark plasma sintering
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