Aluminum Alloy Single Lap Research Articles

Rapid prediction method of failure load for hygrothermally aged CFRP – Aluminum alloy single lap joints

This paper presents an experimental study on the durability of adhesively bonded carbon fiber reinforced polymer (CFRP) – aluminum alloy single lap joints (SLJs) that are undergoing hygrothermal degradation. The failure loads of hygrothermally aged joints were measured and the corresponding fracture surfaces were investigated via visual observation and SEM. The variations of the Tg and the chemical components were determined by the DSC and FTIR analysis, respectively. The results demonstrate that the failure load of joints decreases nonlinearly as the aging duration increases, which approximates the exponential function. Cohesive failure is dominated before and after aging, meanwhile, the moisture absorption plasticizes the adhesive and leads to rougher fracture surfaces. The reduction in Tg and the FTIR results support the occurrence of a hydrolysis reaction in the adhesive due to hygrothermal aging. By quantitatively studying the relationship between the failure loads and the absorbance intensities of functional groups, a failure load prediction method was proposed. This method can establish the correspondence relationship between accelerated aging and actual service aging based on the chemical characteristics of adhesive, and realize the residual performance prediction of the bonding structure after hygrothermal aging rapidly and easily.

Effect of stress rate on shear strength of aluminium alloy single lap joints bonded with epoxy/nanoalumina adhesives

Epoxy adhesive was reinforced with spherical-shaped and rod-shaped alumina nanoparticles. Quasi-static shear strength of aluminium alloy single lap joints was determined as a function of wt.% (0.5, 1.0, 1.5, and 2.0) of alumina nanoparticles in the compression loading. At quasi-static loading, the shear strength of joints with epoxy/nanoalumina adhesives was higher (1.3–1.8 times) than the joints with neat adhesive. Dynamic shear strength of joints with neat adhesive, and epoxy/nanoalumina adhesives containing 1.5 wt% of nanoalumina was analysed. A significant improvement (3–5 times) of dynamic shear strength of joints was obtained over quasi-static shear strength of joints. However, the static and dynamic lap shear strength of joints containing spherical nanoalumina was higher compared to the neat adhesive, and nanoadhesives containing rod-shaped nanoalumina.

Quasi-static and Dynamic Lap Shear Strength of Aluminium Joints Bonded with Epoxy/Alumina Nanocomposite Adhesive

Quasi-static shear strength of aluminium alloy single lap joints was determined as a function of wt% (0.5, 1.0, 1.5, and 2.0) of spherical and rod shaped nanoalumina in epoxy adhesive under compressive loading. Static shear strength for nanoadhesive containing 1.5 wt% of nanoparticles (for both spherical and rod shaped nanoalumina) was observed to be maximum. Dynamic shear strength for neat adhesive and nanoadhesives containing 1.5 wt% of spherical and rod shaped nanoalumina were analysed at two different loading rates using a split Hopkinson pressure bar system. A significant improvement (3 to 7 times) of dynamic shear strength of joints was perceived over static shear strength of joints. Static and dynamic lap shear strength for nanoadhesive containing nanospheres were significantly more than that for neat adhesive and nanoadhesive containing nanorods.

Durability of aluminium alloy adhesive joints in cyclic hydrothermal condition for high-speed EMU applications

The representative adhesive structure of high-speed electric multiple units (EMU) is the side-window, the durability of which is concerned due to the degradation caused by changeable temperature and moisture in hostile service environment. It is of great significance to evaluate the adhesive structure's durability of side-window to prevent bonding failure. In this study, aluminium alloy single lap joints (SLJ), scarf joints (SJ) and butt joints (BJ) were manufactured to conduct accelerated aging tests under cyclic hydrothermal (CH)condition, in which the temperature and moisture vary from 80 °C/95% relative humidity (RH) to −40 °C/30%RH periodically. The adhesive Sikaflex®-265 were studied by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The failure strength of adhesive joints was tested after different aging cycles and the scanning electron microscopy (SEM) was also employed to investigate the microscopic fracture mechanisms. It has been found that the composition, glass transition temperature (Tg), melting temperature(Tm) and thermal stability of adhesive changes after CH aging. The failure strengths of SLJ, SJ and BJ show cubic polynomial descending with aging cycles, and loss about 30% of initial strength after 60 aging cycles. Moreover, the failure mode changes from cohesive failure to mixed failure after CH exposure, which is verified by SEM analysis. The failure criteria before and after CH aging were consistent with quadratic stress criteria, and an equation for a surface describing the variations of quadratic stress criterion with different aging cycles was built, providing reference for the durability evaluation of high-speed EMU's adhesive structures.

Comparative Analysis of Energetic Properties of Ti6Al4V Titanium and EN-AW-2017A(PA6) Aluminum Alloy Surface Layers for an Adhesive Bonding Application

The purpose of this article is to present energetic properties of surface Ti6Al4V titanium as well as surface EN-AW-2017A(PA6) aluminum alloy layers. Values of surface free energy after selected mechanical operations and ozonation were compared. In addition, the influence of different values of ozone concentration on surface layer energetic activation was analyzed. Dispersive and polar components of surface free energy were of particular concern. Comparative evaluation of shearing strength of Ti6Al4V titanium and EN-AW-2017A(PA6) aluminum alloy single-lap adhesive bonded joints were presented. Results can be used as pro-ecological methods of titanium and aluminum alloys preparing for applications where adhesive phenomenon is important.

The Effect of Adhesive for Fillet on Stress in Weld-Bonded Joints

The influence of the fillet with different elastic modulus on the stress distributed in weld-bonded aluminum alloy single lap joint was investigated using elasto-plastic finite element method. The results show that the peak values of the stress along the mid-bondline at the points near the fillet edge were increased as the elastic modulus of the fillet increased. But at points near the both ends of the adherend in over lap zone as well as in the region of the nugget the peak stresses were decreased except longitudinal stress Sx. The peak value of Seqv decreased first, and then it increased again as the elastic modulus in fillet increased. The load-bearing capacity of the whole weld-bonded joints may be improved for the fillet with Adhesive B (825 MPa) for the relative high stress region in nugget was wider and the stress distribution in overlap zone was more uniform.