Comprehensive study on the influence of different pretreatment methods and structural adhesives on the shear strength of hybrid CFRP/aluminum joints

Abstract

The aim of this study was to investigate the influence of laser treatments with varying energy density and wavelength on the surface structure, shear strength and fracture behavior of hybrid compounds of thermoset carbon fiber reinforced polymer (CFRP) and aluminum (Al) bonded with three different structural adhesives. The CFRP was pretreated by laser with near-infrared (NIR) and ultraviolet (UV) wavelengths and applying different energy densities. Aluminum surfaces were structured with NIR. Reference CFRP/Al-specimens were prepared by acetone cleaning, low pressure oxygen/argon plasma or sand blasting. The surfaces were investigated microscopically before bonding and after mechanical testing. In addition, the surfaces were examined with white light interferometer and sessile droplet test methods. The bonded compounds were characterized in standardized single lap shear tests to reveal the influence of the pretreatment strategies on the joint strength. Suitable process windows for laser pretreatments were identified, including NIR-pretreatment methods that can compete with an UV-laser source. For every adhesive, a suitable pretreatment method was found.

Joining of Aluminum and CFRP via Laser Powder Bed Fusion: Influence of Experimental Set-Up and Laser Processing on Microstructure and Mechanical Properties

“…In advance, near-infrared (NIR) laser pre-treatment was carried out to ablate the surface matrix layer from the CFRP substrate, herewith exposing carbon fibers targeting an improved bonding with the AlSi12 melt. The CFRP pre-treatment was conducted according to previous studies, addressing the influence of laser pulse parameters on the matrix and carbon fiber ablation behavior [ 24 ] and correlating them with the bonding strength of hybrid CFRP/Al joints [ 25 ]. Detailed descriptions of the applied laser system and laser parameter with an areal energy density of 0.37 J/mm 2 for the matrix ablation are presented in [ 26 ].…”

Hybrid joining of aluminum alloys and thermoplastic CFR‐PA12 manufactured by IR‐irradiation: Influence of pretreatment and aging on the mechanical properties

“…The screw of the support device was only tightened so far that the support device does not slip on the vertically mounted SLJ‐sample. [ 23 ] For each surface pretreatment, five SLJ‐samples were tested. The given error ranges represent, respectively, the minimal and maximal deviation from the average strength value.…”

“…The phenomena that occur are mainly contact as well as crevice corrosion. [ 22,23 ] Depending on the alloy composition, intergranular corrosion can also occur. [ 2 ] The number of publications on the corrosion behavior of directly joined compounds from thermoplastic CFRP and aluminum is limited, which is why essential findings based on adhesive bonding are included as well.…”

A review of FMLs performance test methods and index evaluation

“…In the seat drop method, the image of the droplet is taken by the high-resolution camera, and the air-liquid interface tangent is made through the junction of gas, solid and liquid, and then the angle is automatically measured by the software. Base method is a fast non-destructive method to characterize the chemistry of material surface, and it is also often used to calculate surface free energy [30,31]. In Wilhelmy test, when a part of the solid is inserted into the liquid, the liquid will rise or fall along the vertical wall of the solid, and the contact angle is determined by measuring the tensile force (thrust) of the liquid on the solid, i.e., the wetting force.…”