Effect of Laser and Plasma Surface Cleaning on Mechanical Properties of Adhesive Bonded Joints

Abstract

The use of adhesives in place of traditional joining techniques as welding and riveting is becoming increasingly common in structural design. Compared to other conventional joining processes, adhesive bonding offers several advantages: including acoustic insulation, vibration attenuation, structure lightening, corrosion reduction and uniform stress distribution. These benefits can be offset if the surfaces to be bonded are not carefully cleaned, degreased and prepared. Many approaches to surface treatments based on physical or chemical modifications have been developed in the years in order to improve the surface activity. Although widely used and very efficient, these techniques present several disadvantages. Physical methods based on mechanical abrasion are supposed to extend bonding area as they increase the roughness, but cause an extensive degradation to the specimens and they are often not easy to reproduce. On the other hand, chemical treatments are typically used with the aim of modifying both morphology and chemical structure of the substrates layers, but they present serious environmental problems of waste disposal, which has moved investigations to an industrial alternative to these processes. According, the use of energetic methods of surface cleaning, such as laser and plasma cleaning processes have been recently consolidated since they are useful to modify the topmost layers of the substrates, increasing their reactivity, without affecting the bulk material properties. These treatments offer an effective and environment-friendly processing of different materials, providing strong and durable bonds with adhesives through modification of the surface morphology and functionalities. In this study, the effects of laser and low pressure plasma treatments on mechanical properties of adhesive bonded joints has been investigated and compared performing lap-shear tests

Experimental investigation on laser milling of aluminium oxide using a 30W Q-switched Yb:YAG fiber laser

“…pre-experimental planning phase) is the solid basis on which a statistical approach was built. Predesign guide sheets were drawn up following the systematic approach to planning the designed experiments proposed in [32][33][34] and successful applied in [7,15,27,28,34,35]. The use of the predesign guide sheets provides a way to systematise the process by which the research team designs the experimental plan.…”

“…Although this kinds of laser source were specifically developed for marking [26], they are so flexible to be adopted in different application, such as: micromachining operations [10,11,13,18] or in surface treatments [27,28,29], nevertheless, here it was adopted because of the good absorption of alumina at the Yb:YAG fundamental wavelength of λ¼1064 nm, the higher pulse power (up to 20 kW), the possibility to have the maximum power (30 W) at all Table 1 Main properties of adopted Al 2 O 3 (declared by the producer).…”

Increasing adhesive bonding of carbon fiber reinforced thermoplastic matrix by laser surface treatment

“…Table shows the detailed characteristics of the laser system. Although this laser source was specifically developed for marking , trimming , and milling different materials, nevertheless, here it was adopted because of the good absorption of carbon fiber at the fundamental wavelength of λ = 1,064 nm, the higher pulse power (up to 20 kW), the possibility to have the maximum power (30 W) at all the frequencies and for the lower power consumption compared to the traditional Nd:YAG laser source (120 W considering only the laser source and the cooling system). The latter characteristic is very important when environment as well as process sustainability are considered .…”

“…In addition, laser machining shows different advantage, such as: absence of tool and tool wear, absence of mechanical contact and complex fixture systems, high flexibility and possibility of automation. Due to its characteristics, laser systems have found several applications in material removal at micro and submicroscale, like in the case of microdrilling ; milling ; marking and, of course, surface cleaning .…”

“…Despite laser cleaning treatments are an emerging technology; there are many studies that demonstrate the effectiveness of this treatment in the surfaces cleaning or in adhesion enhancing . However, in literature, there are a limited number of papers on laser surface treatment of composite materials.…”