Carbon fibre composite materials are increasingly being used in the wind turbine, aerospace, and automotive industries to reduce the structural weight of components due to their high strength to weight and stiffness to weight ratios. However, the anisotropic material properties of Carbon Fibre Reinforced Polymers (CFRP), specifically their electrical and thermal conductivities, create challenges when protecting structures from lightning strike. Moreover, the exposure of CFRP structures/components to electric currents from lightning discharges can cause significant damage. This work investigates the damage inflicted and residual mechanical properties of a CFRP composite material that has been exposed to simulated lightning strike. Seven different CFRP laminate specimens were struck with simulated lightning strike using three different waveforms: the so-called 10/350 mus waveform, which simulates the first return stroke during a direct strike according to IEC 61400-24 Ed1.0, the second was a unipolar long stroke component, and the third was a combination of the first return stroke and the long stroke. Test specimens were prepared from CFRP panels that were damaged due to the lightning strike. The test specimens were subsequently subjected to compression and shear loading to determine the post-strike mechanical properties. The compression tests were conducted using uniaxial coupons and loaded in accordance with ASTM standard D6641. The shear tests were conducted using V-notch specimens utilizing an Iosipescu test rig in accordance with ASTM standard D5379. Digital Image Correlation was used to capture the strain fields on the specimens. The test results were compared against data obtained for pristine CFRP coupon samples that were not exposed to electrical current. The shear and compression strengths, compressive and shear stress-strain curves, compressive and shear moduli, and the maximum temperature captured in the specimens during the tests are presented and discussed. Key results include that the largest reduction of strength occurred in the specimens that were subjected to the largest current and specific energy, and further that damaged specimens respond with a higher degree of nonlinear behaviour than the pristine specimens.
|Title of host publication||Fourth Postgraduate Experimental Mechanics Conference (14/12/18)|
|Publication status||Published - 2018|
- Bristol Composites Institute ACCIS