Optimization of selective laser sintering process parameters for phenolic thermoset composites using X-ray CT analysis

Abstract

Selective Laser Sintering (SLS) is a versatile additive manufacturing technique known for its ability to produce complex and intricate geometries without support structures using various materials. However, achieving the desired isotropic mechanical properties and dimensional accuracy remains challenging with existing thermoplastic polymers. To address these challenges, thermosetting polymers are found to be a suitable option owing to the formation of strong interlayer covalent bonding in three-dimensional (3D) molecular structures at lower temperatures (∼70–80 °C). This study investigates the SLS processing and optimization of phenolic thermoset composites using X-ray computed tomography (XCT) analysis. Phenol-formaldehyde (PF) thermosetting powder was formulated with organic/inorganic fillers and Polyamide 12 (PA12) in five different weight proportions (10wt %-50wt %). XCT was employed as a non-destructive characterization tool to analyse the internal material structure and porosity in the SLS-fabricated samples. By systematically varying the process parameters, mainly laser power and scanning speeds, insights into the effect of these parameters on powder consolidation and porosity are gained. Advanced image processing techniques are utilized to quantify pore size and distribution within the microstructure of printed parts. The XCT-generated porosity data and flexural mechanical strength resulted in 30/70 PA12/PF as an optimal composition (at 8 W laser power and 250 mm/s scan speed) and demonstrated the multi-stage post-curing reduces porosity by 8–10 % while improving flexural strength by 14–16 % due to enhanced crosslinking and formation of interpenetrating polymer network structure. This non-destructive optimization approach elucidates the relationship between process parameters and part quality of SLS 3D printed phenolic thermoset composites, proposing strategies to enhance the performance and reliability of manufactured components for various high-performance applications such as aerospace, biomedical, and energy fuel cells.