In-line monitoring of the fused filament fabrication additive manufacturing process for fibre-reinforced composites

Fused filament fabrication (FFF) is the most widely used additive manufacturing (AM) technique to produce fibre-reinforced polymer matrix composites, due to their low wastage, geometric flexibility and ease of use. However, composites manufactured in this way are highly susceptible to defects such as high void content and poor bond quality at the fibre and matrix interfaces. In the present work, a combination method of Infrared Thermography, Acoustic Emission and micro-computerised tomography was developed for the monitoring of the FFF AM process. Both pure plastic and fibre-reinforced composites were manufactured, and the detection and development of defects created during the printing process were monitored. This combination of techniques allows for detection of defects such as porosity, voids and poor fibre-matrix bonding during printing and the verification of their presence after the printing without the need for destructive testing.