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Combined Fuzzy and Genetic Algorithm for the Optimisation of Hybrid Composite-Polymer Joints Obtained by Two-Step Laser Joining Process
摘要： In the present work, genetic algorithms and fuzzy logic were combined to model and optimise the shear strength of hybrid composite-polymer joints obtained by two step laser joining process. The first step of the process consists of a surface treatment (cleaning) of the carbon fibre-reinforced polymer (CFRP) laminate, by way of a 30 W nanosecond laser. This phase allows removing the first matrix layer from the CFRP and was performed under fixed process parameters condition. In the second step, a diode laser was adopted to join the CFRP to polycarbonate (PC) sheet by laser-assisted direct joining (LADJ). The experimentation was performed adopting an experimental plan developed according to the design of experiment (DOE) methodology, changing the laser power and the laser energy. In order to verify the cleaning effect, untreated laminated were also joined and tested adopting the same process conditions. Analysis of variance (ANOVA) was adopted to detect the statistical influence of the process parameters. Results showed that both the laser treatment and the process parameters strongly influence the joint performances. Then, an uncertain model based on the combination of fuzzy logic and genetic algorithms was developed and adopted to find the best process parameters' set able to give the maximum joint strength against the lowest uncertainty level. This type of approach is especially useful to provide information about how much the precision of the model and the process varies by changing the process parameters.
关键词： genetic algorithms,CFRP,laser cleaning,laser joining,hybrid joints,fuzzy logic
更新于2025-09-16 10:30:52
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Processing of Single-Walled Carbon Nanotubes with Femtosecond Laser Pulses
摘要： There are continued e?orts to process and join single wall carbon nanotubes (SWCNTs) in order to exploit their exceptional functional properties for real-world applications. In this work, we report experimental observations of femtosecond laser irradiation on SWCNTs, in order to process and join them through an e?cient and cost-e?ective technique. The nanotubes were deagglomerated in ethanol by an ultrasonicator and thin slurries of SWCNTs were spread evenly on glass substrates. A laser micromachining workstation for laboratory FemtoLAB (workshop of photonics) has been employed to irradiate the di?erent SWCNTs ?lm samples. The e?ect of laser parameters, such as pulse wavelength, laser power, etc., were systematically tuned to see the possibility of joining the SWCNTs ropes. Several experiments have been performed to optimize the parameters on di?erent samples of SWCNTs. In general, the nanotubes were mostly damaged by the infrared (1st harmonics femtosecond laser) irradiation on the focal plane. However, the less damaging e?ect was observed for second harmonics (green wavelength) irradiation. The results suggest some joining of nanotubes along the sides of the focus plane, as well as on the center at the brink of nanotubes. The joining is considered to be established within the region of the high ?eld intensity of the exposed femtosecond laser beam.
关键词： femtosecond laser,joining,interconnect,SWCNTs
更新于2025-09-16 10:30:52
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Influence of temperature and clamping force on the strength of the joint over different composite-metal combinations joined by laser
摘要： Vehicle weight in automobile industry is a strict limitation which can be overcome with novel material combinations. Laser conduction joining is an arising alternative but it still poses challenges for joining dissimilar metal-composite materials. Up to now, main research lines have been developed using constant process parameters (laser power and clamping force), so, the behavior of these composite-metal joints under different process parameters, and the control of the process itself, are unknown areas of investigation so far. This paper is focused on the implementation of closed-loop control systems for temperature and clamping force. Tests at different set-points have been carried out for different composite-metal combinations, and the strength of the joints has been assessed by single lap shear tests. The optimal joining process parameters have been found for each material combination.
关键词： Quality assurance,Laser joining,Metal-composite joining,Laser bonding,Process control
更新于2025-09-12 10:27:22
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Thermal joining of thermoplastics to metals: Surface preparation of steel based on laser radiation and tungsten inert gas arc process
摘要： Laser-based joining is a potential key manufacturing process for realizing metal plastic hybrids. Therefore, surface preparation is essential to achieve a mechanical form fit. A new approach for surface preparation is based on a tungsten inert gas (TIG) arc process with anodic polarity. This TIG structure was characterized compared to fiber laser manufactured structures in cw and pw mode. The comparison of different preparations was based on pure ultimate tensile strength tests on spot joints. Finally, a transfer to overlap joints was successfully carried out and characterized by tensile shear tests using fiber reinforced plastics.
关键词： laser joining,surface preparation,laser welding,TIG welding,structured steel,metal-plastic-hybrid joints,dissimilar materials,lightweight design
更新于2025-09-12 10:27:22
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Hybrid laser technique for joining of polymer and titanium alloy
摘要： Weight reduction of parts is of great importance in automotive and aerospace industries. Laser direct joining of dissimilar materials had been investigated previously to obtain lightweight characteristics and keep the local excellent plasticity and mechanical property. In the present work, the authors adopt the hybrid laser joining method to bond Ti6Al4V and polyamide (PA66). Laser texturing pretreatment is performed on the Ti6Al4V surface prior to the laser joining process. Oblique microgrooves with the depth ranging from 100 to 550 μm are designed and fabricated on Ti6Al4V surfaces to improve the bonding strength between Ti6Al4V and polyamide. Single lap shear tests are carried out after the laser joining process. The highest breaking force of laser joined Ti6Al4V-PA66 joints reaches around 942 N, which is high up to more than 90% of base PA66 breaking force (1043 N) and about 4.9 times of the joints with a smooth Ti6Al4V surface (194 N). The great enhancement of breaking force of the joints is attributed to the strong mechanical bonding quality between PA66 and surface-textured Ti6Al4V. The employed hybrid laser joining method shows great potential in manufacturing industries.
关键词： hybrid laser joining,interlocking effect,dissimilar materials
更新于2025-09-12 10:27:22
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Assessment of the Microstructure and Mechanical Properties of a Laser-Joined Carbon Fiber-Reinforced Thermosetting Plastic and Stainless Steel
摘要： The thermosetting plastic and stainless steel were joined with a fiber laser. The influence of processing parameters on the joint was studied. The laser scanning on stainless steel is shown to result lathy ferrite precipitates along the boundary, which modifies austenite, while in the second zone, ferrite forms the skeleton structure and separates austenite into a small cellular structure. The laser joining improves the microstructure of both zones. With an increase in the laser scanning speed and power, the shear strength of the stainless steel/plastic joint first increases and then decreases. A low laser scanning speed or high laser power would overheat polyphenylene sulphide and lead to its decomposition. Those factors would also reduce heat transfer and lead to its insufficient melting. The stainless steel/plastic joint acquires a maximum shear strength at a laser scanning speed of 4–5 mm/s and laser power of 320-350 W.
关键词： bonding interface,laser joining,microstructure,carbon fiber-reinforced thermoplastic,stainless steel,shear strength
更新于2025-09-10 09:29:36