A Test Rig for the Calibration of Strain Sensing Carbon Fibre

This paper presents the test equipment developed for the measurement and calibration of sensing carbon fibre. The testing device provides precise load application to a carbon fibre tow and measuring the micro-variations of the fibre electrical resistance in a temperature-controlled environment. The measurement approach based on sensing carbon fibre is a method for strain measurement being recently developed and similar to the traditional strain gauge method. However, due to the integration of the sensing element into the material, it is considered the most promising alternative for carbon fibre reinforced plastic applications. The theory behind fibre strain measurement including the influence of the temperature on the fibre electrical resistance is presented. A detailed presentation of the measurement and calibration device is given including the measurement loop. The test rig is capable of testing fibres at a temperature up to
$180^{\circ}\mathrm{C}$
and the maximum load applied to the fibre of
$1500\mathrm{N}$
. A 5-run test on a T300 3K carbon fibre at
$100^{\circ}\mathrm{C}$
is provided as an example of the test rig operation. On average, the accuracy of the testing method over half load (700N) offers results having a maximum variation of 5% around the mean value of the whole set of test readings collected.