Characterisation of High Performance Polymer Parts Produced by Low Pressure Additive Manufacturing

Additive Manufacturing (AM), also known as 3D printing, using high temperature thermoplastics has been proposed for the production of structures in space. To determine whether this is feasible a systematic study investigating the impact of the space environment on the AM process must be conducted. Existing investigations have focussed on AM in microgravity and AM of either low temperature thermoplastics or individual high temperature thermoplastics at low pressure. This study examines the mechanical characteristics of high temperature, space compatible thermoplastic parts produced by AM in a low pressure environments. Four different thermoplastic filaments were investigated - poly ether ether ketone (PEEK), poly ether ketone ketone (PEKK), and two types of polyetherimide (PEI) (ULTEM 9085 and ULTEM 1010). Their mechanical performance, internal structures and crystallinity were compared to those manufactured under atmospheric conditions. It was observed that the low pressure enabled the manufacture of ULTEM 1010 specimens, which could not be achieved in ambient atmosphere. The low pressure additionally improved the inter-layer adhesion of PEEK and ULTEM 9085 specimens. PEEK, PEKK and ULTEM 1010 specimens exhibited bubbling when printed under low pressure conditions, most noticeable in the compression and H-90° samples, resulting in worse mechanical properties than samples manufactured in atmosphere. The mechanical performance of bending and H-0° specimens remained consistent irrespective of the printing environment, this was thought to be due to conduction to the print bed being the dominant form of heat transfer, resulting in similar thermal histories.