Hybrid carbon fibre/nylon 12 single polymer composites

Abstract

Single polymer composites (SPC) are finding increasing use due to their novel combination of lightweight and high toughness. This paper describes an investigation into the production and properties of hybrid single polymer composites (SPC) made from co-mingled tows of carbon fibres and nylon 12 (PA12) oriented multifilaments, using the Leeds hot compaction process. The aim of the study was to investigate ways to increase the stiffness of the SPC (by the addition of carbon fibres) without significantly compromising ductility and impact performance which a feature of SPCs.Experiments showed that the optimum processing temperature required for the production of the hybrid composites using the hot compaction technique depended on both the arrangement of the hybrid tows and the fraction of carbon fibres. For 22% volume fraction of carbon fibres, a well consolidated sample could be made at a temperature of 176C, 2C below the temperature at which major crystalline melting of the oriented PA12 fibres, and loss of molecular orientation, occurs. For braided cloth made from the same co-mingled tows, a higher temperature of 178C was required to give a well consolidated sample. A combination of wide angle x-ray (WAXS) and differential scanning calorimetry (DSC) measurements showed that this temperature was too close to the melting point of the PA12 multifilaments. For co-mingled tows containing 13% carbon fibres it was found that a well consolidated sample could be made from braided cloth using a lower temperature of 175C. At this temperature, sufficient melted and recrystallised matrix material was produced to consolidate the structure and produce a homogeneous composite. This temperature was 3C below the temperature at which substantial crystalline melting occurred, giving a usable temperature processing window. In tension the hybrid samples were found to fail in a brittle manner, with the whole sample breaking on failure of the carbon fibres. The hybrid samples were found to show ductile behaviour in bending as long as a substantial proportion of the molecular orientation of the PA12 fibres was retained.

Fibre hybridisation in polymer composites: A review

“…Hybrid effects of up to 18% for failure strain were achieved, but the load carrying capacity of the PP fibres was destroyed by the sudden and explosive carbon fibre failure. Another example with a large difference in failure strains is found in Hine et al [144]. Stretch-broken carbon/polyamide yarns were hot compacted into hybrid single polymer composites.…”

The effect of fibre dispersion on initial failure strain and cluster development in unidirectional carbon/glass hybrid composites

“…This means that two types of fibres are combined to form a hybrid composite [6][7][8][9]. The most common hybridisation fibre for carbon fibre composites is glass fibre.…”

Failure behaviour of self-reinforced polypropylene at and below room temperature

“…Several techniques exist for creating the matrix. The most important techniques are film stacking [9,10], co-extrusion [7,11,12] and hot compaction [1,6,[13][14][15][16][17]. The focus here is on the hot compaction process.…”