Engineered thermoplastic polymer composite filaments for through-thickness reinforcement of laminated carbon fibre composites

Abstract

A number of criteria for the property requirements of a through-thickness reinforcement tufting yarn were established. Using these criteria, 23 different polymer yarns were produced as part of this study from 4 different thermoplastic polymers: PEEK, PSU, PPSU, PES. A further study on the influence of nanofillers filler and processing combinations on the mechanical properties of PPSU yarns was undertaken.

Out of these 23 thermoplastic yarns, 10 were selected to be trialled as through-thickness reinforcement tufting yarns. The ability of these yarns to be successfully and consistently tufted into dry carbon fibre was assessed. Following infusion, the influence of the tufting yarns on the mechanical properties of the overall composite was analysed. The properties of these tufted composites were compared with that of non-tufted composite produced under the same processing conditions.

The results of mechanical testing revealed that, in the case of the tension and open-hole tension testing, they are strongly influenced by both the ultimate tensile strength, UTS, of the polymer tufting yarn and the diameter of the tufting yarn, with a larger diameter yarn causing a higher level of fibre misalignment and fibre rupture to the fibres within the composite.

Poor flexural and short-beam shear properties were measured for the tufted composites. It was thought that the resin-rich layer created by the compressed loops from the tufting yarns caused the knock-down observed in these tests.

A minimum UTS for a mechanically beneficial tufting yarn has been proposed.

An alternative test to examine the through-thickness properties of the tufted composite, in the form of the out-of-plane tension test, was examined but the spread in results produced was too large from which to draw any firm conclusions.

A short study into the differences in monofilament and multifilament tufting yarns has also been examined in this project showing the mechanical advantages of multifilament yarns over their monofilament equivalent.

Date of Award	May 2019
Original language	English
Supervisor	Edward Archer (Supervisor), Alistair McIlhagger (Supervisor) & Eileen Harkin-Jones (Supervisor)