Effect of Scanning Mode on Temperature Field and Interface Morphology of Laser Joining between CFRTP and TC4 Titanium Alloy

Hybrid components composed of CFRTP (Carbon Fiber Reinforced Thermoplastic Polymer) and TC4 titanium alloy are increasingly applied in the aerospace field. The scanning mode has a significant influence on the quality of laser joining joint between CFRTP and TC4 titanium alloy. Therefore, the laser joining between TC4 titanium alloy with surface microgrooves and CFRTP has been implemented under oscillating laser joining mode and linear laser joining mode respectively in the present research. The temperature distribution is qualitatively explored based on the established mathematical model of laser joining between CFRTP and TC4 titanium alloy. The interface morphology and the joining strength of CFRTP/TC4 titanium alloy lap joints under oscillating laser joining and linear laser joining are compared. The results indicate that the simulated temperature distribution shows good agreement with the experimental result. Compared with linear laser joining, the oscillating laser joining weakens the heat concentration and creates a heating zone with larger area and more uniform temperature distribution. The interface morphology of laser joining CFRTP/TC4 titanium alloy joints with better resin filling and fewer bubble defects is obtained by oscillating laser joining due to the temperature variation of the form of unequal amplitude oscillations, whereas there are a large number of large-size bubbles in the filling resin and small-sized fusion gaps distributed at the interface with the linear laser scanning mode. By adopting the joining method with oscillating laser scanning mode, higher quality joints can be obtained.

Robust Heterojunctions of Metallic Alloy and Carbon Fiber-Reinforced Composite Induced by Laser Processing

The development of heterojunctions with a strong bonding interface between metals and non-metals has attracted much attention owing to their great potential for use in lightweight structures. Laser joining technology, which emerged as a fast and reliable method, has proven its feasibility and unique advantages in joining metal to polymer matrix composites. Herein, an optimized laser joining configuration has been employed to realize high-quality joining of titanium alloy and carbon fiber-reinforced composite. Cross-sectional microstructures of laser-produced joints reveal that micro-bubbles near the interface have been effectively suppressed and eliminated due to the continual clamping pressure applied to the joined area during the joining process. Tensile tests suggest that the joint strength increases with structure density on a titanium alloy surface, and the greatest fracture strength of joints reaches more than 60 MPa even after experiencing a high–low temperature alternating aging test. For higher structure density (>95%), the joints fail by the fracture of parent plastics near the joined area due to the tensile-loading-induced peel stress at the edges of the overlap region. Otherwise, the joints fail by interfacial shear fracture with breakage when the structure density is lower than 91.5%. The obtained high-performance heterojunctions show great potential in the aerospace and automotive fields.

Laser Transmission Welding of Aluminum Film Coated With Heat Sealable Co-Polyester Resin With Polypropylene Films For Applications In Food & Drug Packaging

The present work deals with the high-power diode laser joining process of aluminum films coated with a polyester resin with polypropylene (PP) films. The first part of the work focused on analyzing the coating process of aluminum films with a polyester resin, using an automatic applicator. The second part of the work was focused on the analysis of the laser joining process of coated aluminum films with plastic counterparts made of PP. Different thicknesses and colors of the PP parts were tested in order to analyze the joining process under a wide range of different conditions. The experimental plan involved the study of the influence of the laser joining parameters, in particular the scanning speed and beam power, on the joints. The joints between aluminum and PP films were subsequently tested by means of tensile and peel-off tests. The results allowed the detection of the best processing conditions, stating the high potential of laser systems in the joining process of aluminum and PP films for food packaging applications.

Welding of Copper to Aluminium With Laser Beam Wavelength of 515 nm

In laser joining of copper (Cu) and aluminum (Al) sheets, the Al sheet is widely chosen as the top surface for laser irradiation because of increased absorption of laser beam and lower melting temperature of Al in contrast to Cu. This research focus on welding from Cu side to Al sheet. The main objective of irradiating the laser beam from the copper side (Cu on top) is to exploit higher solubility of Al in Cu. A significantly lower laser power can be used with 515 nm laser in comparison to 1030 nm. In addition to low laser power, a stable welding is obtained with 515 nm. Because of this advantage, 515 nm is selected for the current research. By fusion of Cu and Al the two sheet metals are welded, with presence of beneficial Cu solid solution phase and Al+Al2Cu in the joint with the brittle phases intermixed between the ductile phase. Therefore the mixed composition strengthens the joint. However excessive mixing leads to formation of more detrimental phases and less ductile phases. Therefore optimum mixing must be maintained. Energy dispersive X-ray spectroscopy (EDS) analysis indicate that large amount of beneficial Cu solid solution and Al rich phases is formed in the strong joint. From the tensile shear test for a strong joint, fracture is obtained on the heat-affected zone (HAZ) of Al. Therefore the key for welding from copper side is to have optimum melt with beneficial phases like Cu and Al+ Al2Cu and the detrimental phases intermixed between the ductile phases

Assessment of mechanical and biocompatible performance of ultra-large nitinol endovascular devices fabricated via a low-energy laser joining process

Nitinol is an excellent candidate material for developing various self-expanding endovascular devices due to its unique properties such as superelasticity, biocompatibility and shape memory effect. A low-energy laser joining technique suggests a high potential to create various large diameter Nitinol endovascular devices that contain complex geometries. The primary purpose of the study is to investigate the effects of laser joining process parameters with regard to the mechanical and biocompatible performance of Nitinol stents. Both the chemical composition and the microstructure of the laser-welded joints were evaluated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). In vitro study results on cytotoxicity demonstrated that the joining condition of 8 Hz frequency and 1 kW laser power showed the highest degree of endothelial cell viability after thermal annealing in 500°C for 30 min. Also, in vitro study results showed the highest oxygen content at 0.9 kW laser power, 8 Hz frequency, and 0.3 mm spot size after the thermal annealing. Mechanical performance test results showed that the optimal condition for the highest disconnecting force was found at 1 Hz frequency and 1 kW power with 0.6 mm spot size. Two new endovascular devices have been fabricated using the optimized laser joining parameters, which have demonstrated successful device delivery and retrieval, as well as acute biocompatibility.

Comparative study on interface morphology and tensile property of CFRTP/Ti6Al4V laser joining joint under various groove dimensions

Laser joining merges as a novel technique for the connection of carbon fiber reinforced thermoplastics composite (CFRTP) and metal. Besides, machining grooves on the metal surface presents a surface pre-treating method to enhance the strength of laser joining joint between CFRTP and metal. In this study, the laser joining of CFRTP and Ti6Al4V alloy is performed with different groove dimensions. The effect of groove dimension on interface morphology and failure load is analyzed. In addition, the formation mechanism of the interface and the fracture mode of the joint are further elucidated. The results indicate that the structurally sound connection and maximum failure load are attained with an appropriate groove dimension (groove width: 0.7 mm, groove depth: 0.25 mm, and aspect ratio: 0.36). At a narrower groove, the bubbles inside the resin caused by thermal decomposition of the matrix resin are obtained, while at a deeper groove, the gaps and holes are observed in the interface of the joint, both resulting in a lower failure load.