The assessment and optimization of heat transfer during electrofusion welding of thermoplastic composite pipes: a modelling and experimental study

Thermoplastic composite pipes (TCP) are typically joined using metallic connectors. With the growing adoption of TCP, there is an increasing demand for alternative joining methods. Electrofusion welding, a well-established technique for joining single-layer thermoplastic pipes, presents a promising alternative. Extending electrofusion coupling to high-pressure TCP could yield a fully non-metallic system, offering benefits such as corrosion resistance, enhanced sealing, and potentially lower costs. However, implementing this welding method effectively requires a coupled Finite Element Analysis (FEA) model with optimization algorithms for parameter estimation to understand the behaviour of the reinforced pipe during welding.

This study employs a least squares optimization approach to estimate missing welding parameters by matching the temperature profiles of simulated models with experimental data at various locations within the pipe/fitting assembly. The simulated data are generated using a 2D FEA model developed in COMSOL Multiphysics software, focusing on the virtual simulation of heat transfer during electrofusion welding of glass-PE TCP. The model accounts for the nonlinear thermal properties of the materials and is calibrated using power input from actual tests.

Experimental data are obtained from welding tests conducted with a standard commercial pipe/fitting product. Temperature fields are recorded throughout the welding cycle using multiple thermocouples positioned at different axial locations and depths within the electrofusion fitting and TCP pipe. The optimization study's results inform the investigation of various electrofusion fitting designs, aiming to achieve a reliable design that meets long-term performance requirements.