Search Results (5)

The conventional near-infrared laser transmission welding (LTW) process for joining dissimilar transparent polymers is limited by the need to incorporate optical absorbents, which compromises joint performance and raises biocompatibility concerns. To address these issues, this study proposed a surface modification technique using femtosecond laser ablation prior to the welding process. Experiments involved 520 nm femtosecond laser ablation of transparent polymers, followed by LTW of dissimilar transparent polymers using an 808 nm laser, with subsequent characterization and mechanical property evaluations. A maximum joint strength of 13.65 MPa was achieved. A comprehensive investigation was conducted into the physical and chemical mechanisms through which laser ablation improved the welding performance of dissimilar transparent polymers. The results demonstrated that laser ablation generated microstructures that serve as substitutes for optical absorbents while also facilitating the formation of numerous oxygen-containing functional groups. These enhancements improve miscibility and bonding performance between dissimilar polymers, enabling absorbent-free welding between ablated polycarbonate (PC) and polystyrene (PS). This work confirms both the feasibility and potential application of this process for direct LTW of dissimilar transparent polymers. Full article

Laser transmission welding (LTW) is an excellent process for joining plastics and is widely used in industry. Numerical simulation is an important method and area for studying LTW. It can effectively shorten the experimental time and reduce research costs, aid in understanding the welding mechanism, and enable the acquisition of ideal process parameters. To enhance understanding of numerical simulation studies on LTW and facilitate research in this area, this paper presents a comprehensive overview of the progress made in numerical simulation of LTW, covering the following aspects: (a) characteristics of the three heat source models for LTW temperature field simulation, including surface heat source model, volumetric heat source model, and hybrid heat source model, along with the methods, results, and applications of temperature field simulation based on these models and experimental validation; (b) numerical simulation of thermal and residual stresses based on the temperature field; (c) numerical simulation of the melt flow field; and (d) predictive simulation of material degradation. The conclusion of the review and the prospects for further research work are eventually addressed. Full article

This study investigates the application of a coupled multi-layer perceptrons (MLP) model with Archimedes optimizer (AO) to predict characteristics of dissimilar lap joints made of polymethyl methacrylate (PMMA) and polycarbonate (PC). The joints were welded using the laser transmission welding (LTW) technique equipped with a beam wobbling feature. The inputs of the models were laser power, welding speed, pulse frequency, wobble frequency, and wobble width; whereas, the outputs were seam width and shear strength of the joint. The Archimedes optimizer was employed to obtain the optimal internal parameters of the multi-layer perceptrons. In addition to the Archimedes optimizer, the conventional gradient descent technique, as well as the particle swarm optimizer (PSO), was employed as internal optimizers of the multi-layer perceptrons model. The prediction accuracy of the three models was compared using different error measures. The AO-MLP outperformed the other two models. The computed root mean square errors of the MLP, PSO-MLP, and AO-MLP models are (39.798, 19.909, and 2.283) and (0.153, 0.084, and 0.0321) for shear strength and seam width, respectively. Full article

The present review provides an overview of the current status and future perspectives of one of the smart manufacturing techniques of Industry 4.0, laser transmission welding (LTW) of semi-crystalline (SC) polymers and their composites. It is one of the most versatile techniques used to join polymeric components with varying thickness and configuration using a laser source. This article focuses on various parameters and phenomena such as inter-diffusion and microstructural changes that occur due to the laser interaction with SC polymers (specifically polypropylene). The effect of carbon black (size, shape, structure, thermal conductivity, dispersion, distribution, etc.) in the laser absorptive part and nucleating agent in the laser transmissive part and its processing conditions impacting the weld strength is discussed in detail. Among the laser parameters, laser power, scanning speed and clamping pressure are considered to be the most critical. This review also highlights innovative ideas such as incorporating metal as an absorber in the laser absorptive part, hybrid carbon black, dual clamping device, and an increasing number of scans and patterns. Finally, there is presented an overview of the essential characterisation techniques that help to determine the weld quality. This review demonstrates that LTW has excellent potential in polymer joining applications and the challenges including the cost-effectiveness, innovative ideas to provide state-of-the-art design and fabrication of complex products in a wide range of applications. This work will be of keen interest to other researchers and practitioners who are involved in the welding of polymers. Full article

Polypropylene and PA66 are widely used in our daily life, but they cannot be welded by laser transmission welding (LTW) because of polar differences and poor compatibility. In this paper, grafting modification technology is used to improve the welding performance between polypropylene and PA66. Firstly, the strong reactive and polar maleic-anhydride (MAH) is grafted to polypropylene and infrared spectrometer is used to prove that MAH has been grafted to polypropylene. At the same time, the mechanical and thermal properties of the graft modified polypropylene (TGMPP) are tested. The results prove that the grafting modification has little influence on them. Also, the optical properties of TGMPP are measured. Then, the high welding strength between TGMPP and PA66 is found and the mechanism of the weldability is researched, which shows that there are two reasons for the high welding strength. By observing the micro morphology of the welding zone, one reason found is that the modification of polypropylene can improve the compatibility between polypropylene and PA66 and make them easy to diffuse mutually, which causes many locking structures formed in the welding region. The other reason is that there are chemical reactions between TGMPP and PA66 proved by the X-ray photoelectron spectrometer. Full article