Laser intensity and surface distribution identification at weld interface during laser transmission welding of thermoplastic polymers: A combined numerical inverse method and experimental temperature measurement approach

Abstract

The determination of the laser intensity profile necessary to weld two thermoplastic parts is crucial for understanding and optimizing the laser welding process in polymers and composite materials. Traditional methods of measuring the laser beam intensity profile, such as laser beam profiling techniques, can be difficult to implement and expensive. In this paper, we present the development of a technique that combines a numerical inverse method with experimental temperature measurements to determinate the laser intensity distribution at the weld interface. This technique does not require specialized or expensive equipment and accounts for variations in laser beam intensity caused by different components and interfaces. The technique uses thermocouple sensors to measure interface temperatures during welding, and an analytical gaussian model to estimate the laser intensity distribution at the weld interface. The model is then used as input data in a numerical heat transfer model. The technique is validated through experimental investigations on transparent and absorbent Polylactic acid polymers.

Investigating the Effect of Interface Temperature on Molecular Interdiffusion during Laser Transmission Welding of 3D-Printed Composite Parts

“…The cooling was instantaneous following the passage of the laser on each thermocouple via thermal conduction and natural convection. In comparison with our previous research conducted on thermoplastic PLA [ 40 ], the cooling rate was accelerated as a result of the higher thermal conductivity of the CCFPC compared to the pure thermoplastic PLA.…”

“…The cooling was instantaneous following the passage of the laser on each thermocouple via thermal conduction and natural convection. In comparison with our previous research conducted on thermoplastic PLA [40], the cooling rate was accelerated as a result of the higher thermal conductivity of the CCFPC compared to the pure thermoplastic PLA. For the LTW process with a constant scanning speed of the laser, except for the two end sections of the part subjected to boundary effects, the thermal history of all perpendicular lines to the weld seam was considered to be identical.…”

“…The instantaneous temperature profile along a perpendicular line to the weld seam has been demonstrated to have a Gaussian shape [ 40 , 41 ]. Based on the outcomes presented above, it is evident that employing a Gaussian-fitted model makes it possible to generate a temperature profile for every temporal instance (see Figure 7 a).…”