“…To do so, a new parameter called “corrected effective stress”, , was defined. Sousa et al 49 proposed a fatigue life prediction model based on a specific parameter, defined as “effective stress”. The model proposed by the authors made it possible to eliminate the effect of loading angle, by combining three different mode mixities (mode I, mode II, and mixed mode (45°)) in one single master curve.…”
Section: Resultsmentioning
confidence: 99%
“…As a result, a new corrected effective stress, , is proposed as Equation (4) where the effective stress suggested by Sousa et al 49 is multiplied by the ratio between the strength of the joint at a considered temperature and mode mixity to the strength of the same joint tested at room temperature: is mode mixity and is the considered high temperature.…”
Section: Resultsmentioning
confidence: 99%
“…The results are used to calculate the fatigue stress parameter considered in the master S–N curve. The proposed fatigue stress parameter is an extension of an already developed model 49 . The extended model can be used for fatigue life analysis of adhesive joints at high temperatures.…”
Despite existing studies on the effects of temperature on the behavior of bonded joints, the role of loading mode and test type (strength, fatigue, and fracture tests) on the rate of degradation of adhesive/joint properties at high temperatures has not been adequately investigated. The aim of the current study is to determine if adhesives experience the same rate of degradation at high temperature when they are subjected to different mode mixities. To do so, an epoxy adhesive was subjected to strength, fracture, and S–N fatigue tests, for modes I and II, at different temperatures. The results show that there is a significant difference between the rate of degradation in mode I/tensile and mode II/shear loading conditions. It was also found that the rate of degradation in adhesive properties is a function of test type. Based on the results, by increasing the temperature, a less reduction in tensile strength was found in the Arcan joints (almost 50% reduction) compared with the dogbone specimen (where the strength was reduced by less than 40%). According to the results, for all the considered tests, temperature sensitivity was more noticeable in tensile loading conditions compared with the shear mode. It is shown that despite the reduction in tensile fracture energy with temperature (by around 23%), the shear fracture energy was improved (by over 20%) at 50°C. Based on these results, an S–N model was also developed to create a master S–N curve, plotted as a function of temperature.
“…To do so, a new parameter called “corrected effective stress”, , was defined. Sousa et al 49 proposed a fatigue life prediction model based on a specific parameter, defined as “effective stress”. The model proposed by the authors made it possible to eliminate the effect of loading angle, by combining three different mode mixities (mode I, mode II, and mixed mode (45°)) in one single master curve.…”
Section: Resultsmentioning
confidence: 99%
“…As a result, a new corrected effective stress, , is proposed as Equation (4) where the effective stress suggested by Sousa et al 49 is multiplied by the ratio between the strength of the joint at a considered temperature and mode mixity to the strength of the same joint tested at room temperature: is mode mixity and is the considered high temperature.…”
Section: Resultsmentioning
confidence: 99%
“…The results are used to calculate the fatigue stress parameter considered in the master S–N curve. The proposed fatigue stress parameter is an extension of an already developed model 49 . The extended model can be used for fatigue life analysis of adhesive joints at high temperatures.…”
Despite existing studies on the effects of temperature on the behavior of bonded joints, the role of loading mode and test type (strength, fatigue, and fracture tests) on the rate of degradation of adhesive/joint properties at high temperatures has not been adequately investigated. The aim of the current study is to determine if adhesives experience the same rate of degradation at high temperature when they are subjected to different mode mixities. To do so, an epoxy adhesive was subjected to strength, fracture, and S–N fatigue tests, for modes I and II, at different temperatures. The results show that there is a significant difference between the rate of degradation in mode I/tensile and mode II/shear loading conditions. It was also found that the rate of degradation in adhesive properties is a function of test type. Based on the results, by increasing the temperature, a less reduction in tensile strength was found in the Arcan joints (almost 50% reduction) compared with the dogbone specimen (where the strength was reduced by less than 40%). According to the results, for all the considered tests, temperature sensitivity was more noticeable in tensile loading conditions compared with the shear mode. It is shown that despite the reduction in tensile fracture energy with temperature (by around 23%), the shear fracture energy was improved (by over 20%) at 50°C. Based on these results, an S–N model was also developed to create a master S–N curve, plotted as a function of temperature.
“…It should be noted that the endurance limit in J‐N method is much lower than the S‐N in normal fatigue, that means the cyclic impact loading is extremely more destructive compared with the normal fatigue loading. In the normal fatigue (S‐N approach) the endurance limit is around 50% of the static strength of the bonded joints 27 while the endurance limit is less than 8% of the impact strength of the adhesives in the impact fatigue loading conditions.…”
One of the most efficient methods of improving the strength of adhesive bonds is the bi-adhesive technique. The main aim of the current study is to investigate the fatigue life of bi-adhesive joints under cyclic impact loads based on the J-N (impact energy vs. fatigue life) methodology. To achieve this, single lap joints were subjected to cyclic low energy impacts. The J-N curves were constructed using the experimental data considering Basquin's equation.According to the results, the durability of the joints against impact fatigue loads can be improved significantly (up to 17 times higher for the tested joints) using the bi-adhesive technique. The results also showed that the impact fatigue life is very sensitive to the length ratio of the ductile to the brittle adhesives in bi-adhesive joints. It was found that the total absorbed energy of the joints increases significantly by the reduction of the impact energy.
“…The ready-to-use adhesive is then poured into the silicone mould and is cured inside an oven at 30°C for 48 h. The specimens are tested after two weeks, allowing them to fully cure and reach their final strength. 19,20 Figure 4 also displays the finished dumbbell-shaped specimens of EP, GO-EP, and G-EP bulk specimens, respectively.Figure 4.Bulk specimens of (a) EP, (b) GO-EP, and (c) G-EP (all dimensions in mm).…”
The addition of nano-additives provides a path to improve joint performance. However, it is not clear if the use of these materials can alter the susceptibility of bonded joints to the presence of defects. This work aims to shed some light on this matter, by testing the performance of defective joints bonded with adhesives modified with nano-additives. Two different kinds of carbon-based nano-platelets, including graphene (G) and graphene oxide (GO), were used in this work as additives for adhesives used to bond single lap joints (SLJs). Bulk specimens, as well as three geometrically different SLJs were manufactured and tested. One configuration was manufactured without defects (WO), another with a disbond defect in the middle of the overlap, and another with a disbond defect on the edge of the overlap, known as a side defect (SD). These specimens were bonded with a neat epoxy adhesive and with the same adhesive modified with the addition of 0.3 wt% of G and GO. The addition of G and GO was found to improve Young’s modulus and the strength of the epoxy adhesive, while also decreasing its toughness. Dual effect of G and GO addition on improving the strength of the neat epoxy and WO SLJs while reducing the strength of some defective SLJs is also discussed using FT-IR and Raman spectrometry as well as scanning electron microscope pictures of the fracture surfaces.
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