Abstract
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.
Highlights
Thermoplastics have been used widely in manufacturing industries, especially in the medical and other industries
These studies help us to understand that an optimum value of laser power enhances the weld strength, which may be due to an increased depth of penetration and weld width during Laser Transmission Welding (LTW)
During the electromagnetic interference shielding studies, Verma et al [206] found no loss for MWCNTs for temperatures up to 500 ◦C for PPCP, but at 500 ◦C, the mass losses were more than 99.82%
Summary
Thermoplastics have been used widely in manufacturing industries, especially in the medical and other industries. Various types of laser welding are available based on; laser source: continuous, pulsed, solid-state, gas, diode, and fibre; the geometry of materials: butt, corner, edge, lap, and T-joint; nature of the interaction between laser and material: direct, surface heating, through transmission; and laser beam delivery: contour, simultaneous, quasi-simultaneous and masked [27,28,29,30]. Laser sources such as Nd: YAG, diode and fibre lasers, can be selected based on operating wavelength suitable for LTW of polymers and their composites. To achieve a strong joint or weld integrity, it is highly essential to understand the laser process parameters’ specifications and capability, factors leading to weld defects, welding mechanism, and the materials’ properties [45]
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