Carbon fiber is increasingly being utilized as a reinforcing material due to its high strength and high modulus, which is imparted into the properties of the final composite. A comprehensive review of the carbon fiber production process, from polymerization to fiber spinning and stabilization and carbonization, is provided. Relationships between carbon fiber microstructure and material performance is undertaken in order to assess the current status of the mechanical, thermal, and electrical properties of commercially available PAN and pitch based carbon fibers, as well as recently developed experimental carbon fibers. A discussion of next generation carbon fibers is also provided, with a discussion on carbon fiber derived from alternative precursor materials, as well as hierarchical carbon fiber composites.

Processing, structure, and properties of carbon fibers

Fabrication of low-cost carbon fibers using economical precursors and advanced processing technologies

High modulus polyethylene fibres: preparation, properties and modification by crosslinking

Polymer molecules respond to the application of stress by disentanglement, chain orientation and bond rupture. Being the last step in this series of events, the efficiency of flow-induced mechanochemical degradation depends markedly on the details of the pervading flow field. From the results of fluid mechanics, it is usual to distinguish degradation in simple shear flow from degradation in elongational flow. Polymer dynamics require a further subdivision between transient elongational flow, characterized by a short residence time (less than the chain relaxation time τ 1) in the high strain rate region, from quasi-steady-state elongational flow which possesses a stagnation point and a long residence time Open image in new window . This chapter reviews the main factors which influence the degradation kinetics in transient elongational flow, exemplified by flow through a narrow contraction and ultrasonic irradiation. The experimental results reveal a fundamental difference in the kinetics of chain scission in transient and stagnant conditions. Differences in the characteristic residence time prevalent in each type of flow permits one to probe the different stages of the chain unravelling process up to the point of bond rupture. It is suggested that the intricate degradation behavior observed in transient elongational flow stems from the compact nature of the weakly deformed molecular coil. This favors intramolecular interactions during the dynamics of deformation.

https://link.springer.com/content/pdf/10.1007%2FBFb0051636.pdf

Mechanochemical degradation in transient elongational flow

Morphology, phase composition, and molecular mobility for a series of semicommercial gel-spun UHMWPE fibers were studied using a combination of WAXS, SAXS, and 1H solid-state NMR methods. The fibers show uncommon for this type of fibers decrease in the break load with increasing draw ratio, whereas their modulus and the tenacity reach very high ultimate values. The X-ray and NMR methods have provided complementary information about the fiber morphology and structural reorganizations occurring at the final stage of the fiber drawing. The results suggest that the fiber morphology can be described by a mixture of crystalline fibrils with long period of ∼35–45 nm, as shown by SAXS, and large, so-called, chain-extended crystals. The presence of large crystals with embedded defects is shown by NMR. The drawing causes increase in the crystallinity from ∼89 to ∼96 wt % and in chain orientation, while the long period of fibrils and the break load of fibers surprisingly decrease. The decrease in the long period wit...

Morphology, Chain Dynamics, and Domain Sizes in Highly Drawn Gel-Spun Ultrahigh Molecular Weight Polyethylene Fibers at the Final Stages of Drawing by SAXS, WAXS, and 1H Solid-State NMR

The mechanical properties of amorphous carbon fibres, derived from linear low density polyethylene strongly depend on the fibre diameter, which may be attributed to the presence of a skin/core structure in these fibres. High strength carbon fibres could thus be prepared by using thin precursor filaments, that are obtained by a melt-spinning process, in which the spinline is stretched at an elevated surrounding temperature. Careful carbonization of these precursors gives carbon fibres with a strength of 2.16 GPa, a modulus of 130 GPa and a high strain at break of 3%.

The effect of diameter on the mechanical-properties of amorphous-carbon fibers from linear low-density polyethylene

The fraction of load carrying chains in various gelspun/hotdrawn ultra high molecular weight polyethylene (UHMWPE) fibres was evaluated on the basis of a recent morphological model A linear relation was found between the strength of the fibre and the fraction of load carrying chains, calculated by this method By extrapolation of this relation to a fraction of load carrying chains of unity, a theoretical strength of 30±3 GPa was estimated for polyethylene

On the theoretical strength of gelspun/hotdrawn ultra-high molecular weight polyethylene fibres

In the continuous drawing of gel-spun UHMWPE fibres, the diameter of the undrawn fibre appears to have a pronounced effect on its drawing behaviour and on the mechanical properties of the resulting hot-drawn fibres. A highly oriented structure is developed more efficiently upon drawing of thinner fibres, which may be attributed to differences in the deformation mechanism between as-spun fibres of various diameters. By drawing of thin fibres, UHMWPE filaments having a strength of 6.0 GPa and a Young's modulus of 222 GPa can be obtained at a relatively low draw ratio of λ=70.

J. P. Penning

Papers

The effect of diameter on the mechanical-properties of amorphous-carbon fibers from linear low-density polyethylene

On the theoretical strength of gelspun/hotdrawn ultra-high molecular weight polyethylene fibres

The effect of fiber diameter on the drawing behavior of gel-spun ultra-high-molecular-weight polyethylene fibers