Micrograph 618 and full record

Micrograph no

618

Brief description

Fracture surface of a carbon fibre composite

Keywords

alignment, carbon, carbon fibres

, CFC, composite material

, epoxy

, fibre

, fracture $Link to MATTER Glossary entry for fracture$ , neutral axis

, polymer

, polymer composite, pull-out

, reinforcement

, tensile

Categories

Composite, Fracture, Polymer, Polymer composite

System

CCcomposite

Composition

Carbon fibre, epoxy resin matrix

Standard codes

Reaction

Carbon fibres are produced by oxidising polyacrylonitrile in air at 230 deg C whilst applying tension, and then carbonising the product in nitrogen at 1000 deg C

Processing

A crude carbon fibre composite was made by laying out 40 tows of fibre, painting them with epoxy resin, compressing them in a mould, and curing them for five hours at 100-190 degrees C

Applications

Carbon fibre composites are used as a structural material in the aerospace and automotive industries, as well as in certain high-performance sporting equipment. They present exceptional stiffness and can be structurally optimised for particular load-bearing applications.

Sample preparation

The bar has been bent to failure in a three-point bending rig.

Technique

Scanning electron microscopy (SEM)

Length bar

600 μm

Further information

The neutral axis is clearly visible, up the centre of the image, with a region of ragged fibres indicating tensile failure to the left, and a smother, apparently crushed surface to the right where the beam was in compression. The holes and proud fibres in the tensile region are indicative of fibre pull-out which is a toughening mechanism in fibre composites.

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