چكيده به لاتين
Structural adhesive joints have advantages such as reduced stress concentration and high strength to weight ratio. However, due to the viscoelastic nature of polymer based adhesives, they do not have sufficient strength to withstand under long-term fixed loads and therefore over time with the loss of their stiffness, they experience creep deformation.
The aim of this study is to evaluate the effect of adding graphene oxide nanoplates (GONPs) on the creep behavior of single lap joints adhesives (SLJ) under different temperatures and stress levels. So the static tensile tests was conducted on the neat and reinforced samples with 0.1 and 0.3 wt% of GONPs at 40, 50 and 60°C. The highest shear strength improvement was obtaibed at 0.1 wt% of GONPs compared to naet adhesive.This improvement was 15.5, 5.7 and 6% at 0.1 wt% of GONPs compared to naet adhesive and was 15.5%, 5.7% and 6% at temperature of 40, 50 and 60°C, recpectively.
Also tensile creep tests were performed at 40 and 50°C and stress levels of 25% and 35% of the shear strength and 0.1 and 0.3wt% of GONPs. The results showed that the highest creep strength obtained at 40 °C and 1.0 wt% of GONPs.The maximum reduction of Creep displacement was 42% and 55% related to 0.1wt% of GONPs at stress levels 25% and 35% compared to neat adhesive. The initial slope of the first creep stage showed a reduction of 76% and 81% at 25% and 35% of stress levels, respectively and the slope of second creep stage reduced by 91% and 75% at 25% and 35% of stress levels.
At 50 ° C which is about the glass transition temperature (T_g) of the adhesive, creep resistance of the adhesive decreased considerably. At this temperature the maximum reduction of creep displacement obtained at 0.3 wt% of GONPs and was 76% and 31% for 25% and 35% stress levels, respectively. Also, the minimum reduction of initial slope of primery creep stage and the slope of second stage were 70% and 84% compared to naet adhesive that obtained at 3.0 wt% of GONPs for 25% of stress level.
