TWENTY-SECOND INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS (ICCM22) THERMOGRAPHIC ASSESSMENT OF FIBRE REINFORCED 3D PRINTING FILAMENT DingYi Monique Huang, Rachael C. Tighe * and John S. McDonald-Wharry School of Engineering, University of Waikato, Hamilton, New Zealand *rachael.tighe@waikato.ac.nz Keywords: 3D printing, Pulsed phase thermography, Natural fibre reinforced composites, Non- destructive evaluation, Infrared thermography ABSTRACT This research demonstrates the feasibility of active thermography for online inspection of 3D printing filaments has and its potential to be used to provide quality assurance of short and natural fibre reinforced composites. 3D printing of materials is widely used across a range of industries. Natural fibre composites materials offer sustainable and cost-effective solutions to material challenges. When considering combining natural fibres and 3D printing there are several manufacturing challenges that must be overcome. The focus of this research is to ascertain if active thermography is a suitable tool for online inspection of fibre reinforced filaments used for 3D printing composites. The aim of the inspection is to identify fibre rich and fibre poor regions along the filament, where uniformly distributed fibres along the filament is preferred. Regions with a locally high weight percent of fibres, known as a fibre bunch, can cause problems when used to print a part resulting in a waste of materials and failed print jobs. The paper presents a feasibility study showing the potential of using pulsed thermography to identify fibre bunching. An external heating stimulus is applied to the filament and an infrared detector is used to monitor the thermal decay. The thermal contrast produced by fibre bunches compared to regions of uniformly distributed fibres is used to identify potential problem areas and provide a means of quality control. Investigation includes variation of the heating stimulus, data collection and data processing routines. 1 INTRODUCTION 3D printing of composite materials has the potential to combine the ability to tailor material properties to the application, as provided by composites, with the reduction of waste and ability to manufacture more complex parts, as provided by 3D printing [1]. Short fibre reinforced composites allow a wider range of reinforcements to be used than typical continuous fibre counterparts including use of recycled materials and natural fibres [2]. Thermoplastic composite materials with short fibre reinforcement are typically extruded into a filament form that can then be fed into Fused Filament Fabrication (FFF) or Fused Deposition Modelling (FDM) 3D printers. The ideal filament should be uniform in diameter as well as in reinforcing fibre distribution. Inconsistencies in the filament can cause problems during printing and may be passed on to become flaws in the printed part. Uneven distribution of fibres, or bunching, is of concern as this has the potential to lead to a variation in mechanical properties of the part [3]. Fibre bunching may also lead to nozzle blockages during printing, disrupting print jobs and resulting in material waste and down time [4]. Some of these issues can be addressed by heating the printer nozzle [5]. The present research takes the approach that if we can quality assure the materials going into the printer the part that is produced cannot be impacted by variations in the filament properties. Various polymer-based composite parts are now successfully produced with 3D printing; these include Carbon/Graphite fibres, fiberglass and natural fibres. Reinforcements in 3D printed parts can be either continuous, long fibre or short fibre. There are more options for short fibre reinforcements than their typical continuous fibre counterparts including the use of recycled materials and natural fibres. For continuous fibre reinforcement spools of separate fibre and matrix material are fed directly