1：Experimental Design and Method Selection

The study used laser transmission welding (LTW) with a thulium fibre laser to join unfilled PTFE with PTFE filled with 10 wt.% short carbon fibres. Different settings for laser power and speed were applied to examine their influence on the lap shear strength of the weld.

2：Sample Selection and Data Sources

Samples were provided by Parker Hannifin Manufacturing Belgium as strips of 1.50 mm thick, which were cut into small plates of 24.0 x 24.0 x 1.50 mm3. The samples were polished to ensure a low surface roughness.

3：List of Experimental Equipment and Materials

LPKF Precisionweld 3000 machine equipped with a thulium fibre laser, Keyence microscope, High-Energy CT system Optimized for Research (HECTOR) device, Vick tensile machine, TA Instruments Q50 device for TGA, TA Instruments Q2000 for DSC, PerkinElmer Frontier spectrometer for ATR-IR, Bruker Avance II with a 500 MHz magnet for NMR spectroscopy.

4：Experimental Procedures and Operational Workflow

The welds were performed using a laser power of 8 W, 12 W, and 16 W at speeds of 5 mm/s, 10 mm/s, and 15 mm/s. The samples were characterized using μ-CT, optical microscopy, lap shear tests, DSC, ATR-IR, and NMR spectroscopy.

5：Data Analysis Methods

The lap shear strength was measured, and the interior of the welded zone was examined using μ-CT. DSC was used to determine the heat of crystallization and the melting temperature of the PTFE-compounds. ATR-IR and NMR spectroscopy were used to evaluate potential degradation products.