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- MakaleYalnız künye2021Scopus SJRQ1An investigation of the fatigue performance of adhesively bonded step-lap joints: An experimental and numerical analysis
Gavgali, Esma; Sahin, Resul; Akpinar, Salih
Adhesively bonded joints are used in many engineering applications and are manufactured by joining various materials together. Static and dynamic analysis of adhesively bonded joints is very important in both scientific and sector studies on these joints. In this study, the static and fatigue strengths of single-lap joints (SLJs) and three-step-lap joints (TSLJs) that were subjected to tensile and four-point bending tests were examined experimentally and numerically. Adhesively bonded joints were produced using DP460 toughened type adhesive and AA2024-T3 aluminum alloy was used as the adherent. Fatigue tests were performed at a loading ratio (R) of 0.1 and a frequency of 10 Hz. As a result, applying a step-lap to the overlap area of adhesively bonded joints considerably increased the tensile static and fatigue strength of the joint. For the single-lap joint, both the static tensile and the tensile fatigue lifetime limit value of the three-step-lap joint increased approximately 100%. One of the reasons for that increase was that the moment effect formed in single lap joints due to the eccentric loading is minimized and the other is that a step-lap applied to the overlap area retards the formation of damage. However, static bending and fatigue strength values of TSLJs significantly decreased compared to those of SLJs. In addition, the results of the experimental and numerical analyses were found to be highly compatible with each other.
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İncele - MakaleYalnız künye2021Scopus SJRQ1The effects of nanostructure additive on fracture strength in adhesively bonded joints subjected to fully reversed four-point bending fatigue load
Demir, Kübra; Gavgali, Esma; Yetim, Ali Fatih; Akpinar, Salih
Structural adhesive joints used in aerospace are usually subjected to fatigue loading rather than static loading. This study experimentally and numerically investigated the static four-point bending loads of adhesively bonded joints after fully reversed four-point bend fatigue loading where nanoadhesives – obtained by adding carbon nanostructures into aerospace grade structural adhesive – were used to bond the joints. Single lap joint specimens were produced using a nanocomposite adhesive obtained by adding 1 wt % graphene, 1 wt % carbon nanotubes-COOH and 1 wt % fullerene C60 nanostructures to a DP460 structural adhesive. AA2024-T3 aluminum alloy and carbon fiber-reinforced composites (CFRCs) with a plain weave fabric (0/90°) were used as adherend materials. First, static four-point bending tests were applied to these joints to obtain their strengths and then fully reversed sinusoidal fatigue tests were applied under a constant load amplitude, a frequency of 20 Hz and a load ratio of R = −1. Fatigue tests were performed over 1,000,000 cycles – accepted as an infinite life – at four different load levels by considering the strengths obtained from the static tensile tests. After obtaining the static four-point bending strengths of the joints to which fatigue loading was applied, the changes in the strengths of joints with and without fatigue testing were examined. The static strengths of aluminum joints bonded with nanoadhesive and subjected to fully reversed fatigue loading significant increased, depending on the nanostructure type added to the adhesive. Moreover, such increases in the strengths of joints are highly dependent on the adherend type (composite with [0/90]6 stacking sequence or AA2024-T3 aluminum).
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