RESUMEN
One of the most commonly applied methods of joining dissimilar materials is gluing. This could be mainly attributed to the applicability of this technique in various industries. The article presents a method of material surface treatment, which increases the shear strength of adhesive joints for lightweight metals such as aluminum with plastics. For this purpose, laser surface microstructuring was performed on each of the selected construction materials. As a result of the performed treatment, the active surface of the glued area was increased, which increased the adhesive strength. The picosecond laser with UV radiation used in the research is TruMicro 5325c with which material can be removed as a result of the cold ablation phenomenon. The applied parameters of the laser device did not cause thermal damage to the surface of the microstructured materials, which was confirmed by microscopic examination. Laser micromachining did not deteriorate the degree of wetting of the tested materials, either, as was confirmed by the contact angle and surface energy measurements with the use of water as the measuring liquid. In investigated cases of microstructure types, the presented method significantly increased the shear strength of the joints formed, as demonstrated by the presented strength test results. Research has shown that created joints with microstructure made according to the described method, are characterized by a significant increase in strength, up to 376%, compared to materials without microstructure. The presented results are part of a series of tests aimed at selecting the operating laser parameters for the implementation of geometric shapes of microstructures which will increase the strength of adhesive joints in selected materials.
RESUMEN
In this paper, an experimental investigation of the ablation plasma generated from the copper substrate by means of nanosecond laser pulses is presented. We studied the evolution of the ablation plasma in the first 1000 ns after plasma onset using the fast-gated imaging and optical emission spectroscopy methods. Plasma imaging showed that the expansion of the plume front can be described using a so-called drag model, with the expansion limit increasing with laser fluence from 254 µm for 30J/cm2 to 375 µm for 67J/cm2. By using the Boltzmann plot and Stark broadening methods, it was found that within the first microsecond after onset, the electron excitation temperature and electron number density decrease from 1.2 eV to 0.8 eV and from 4×1016cm-3 to 5×1015cm-3, respectively. Using the McWhirter criterion, we confirmed that in the considered time range the plasma remains in a state of local thermodynamic equilibrium.