Surface Characterization of Carbon Fiber Polymer Composites and Aluminum Alloys After Laser Interference Structuring

Laser-Interference Surface Preparation for Enhanced Coating Adhesion and Adhesive Joining of Multi-Materials (Final Project Report)

“…a laser fluence of 1.6 J/cm 2 , the effective convection time was estimated to be approximately 25 ns (Lasagni et al 2007). Based on the experimental and model simulation results (Lasagni et al 2007), the surface morphology due to laser-interference processing is dependent on the laser fluence as indicated in Figure 2 (Sabau, Greer, et al 2016), as follows: (a) at low laser fluences, the material melts and stays at maxima locations as the temperature gradients are small and Marangoni forces are small, (b) at moderate laser fluences, the material starts to be removed from interference maxima locations resulting in a double-peak geometry, and (c) at high fluences, the residence time of the metal is increased and the two fluid fronts coming from the two maxima-interference coalesce (and it could also be affected by the evaporation and vapor pressure). The major gap in the current-state-of-the art lays in the application of the laser-interference technique to the as-received Al and Ti surfaces.…”

“…Briefly, the laser-interference structuring of the Al alloys can be explained by the induced photothermal effect that creates a periodic heat treatment according to the spatial power distribution due to the waveinterference (Sabau, Greer, et al 2016). As a result of photon absorption and metal properties, Al will melt and evaporate when its temperature rises above its melting point and saturation temperature at atmospheric pressure, respectively.…”

“…In addition to the basic physical phenomena, which were reviewed in the above paragraph for the laser-interference structuring of Al with well-polished surfaces, it has to be mentioned that additional phenomena take place during the laser-interference structuring of the Al in the as-received condition. For the as-rolled Al5182 sheet material, the resulting surface morphologies, which were noted at ORNL (Sabau, Greer, et al 2016)due to the melting and subsequent fluid dynamics at the microscale, were:…”

“…The coherent laser beams create an interference pattern in the overlap spot. As shown in Figure 3, The laser pulse fluence (pulse energy per unit area) was increased by using identical lenses in each beam path in order to decrease the spot size to 5 mm or 6 mm from the original beam size of 8 mm (Sabau, Greer, et al 2016;Meyer, Sabau, and Daniel 2019). The periodicity between power peaks and the resulting laser-interference induced undulations (d), is defined by the wavelength, λ, and the angle, α, between the two beams, as 𝑑 =…”

Buried interfaces – A systematic study to characterize an adhesive interface at multiple scales

“…Laser treating has gained much interest in the past decades for metallic surfaces since this technically simple and environmentally benign approach is highly efficient [9][10][11][12]. Lasers clean and restructure by ablating the surface [13][14][15] while, depending on the process atmosphere, they simultaneously chemically functionalize the surface by forming, for example, surface oxides, oxo-nitrides or nitride films [10,[16][17][18]. As a consequence, laser treatment enhances bond strengths and longterm stabilities of metal-polymer joints, though the fundamentals of this improvement remain under debate [19][20][21][22][23].…”