The ageing evaluation of aircraft cables insulation layer under electrical working conditions
摘要
One of the primary causes of failure in aircraft electrical systems is electro-thermal ageing of cable insulation, which has a detrimental impact on the safety of aircraft operation. In this paper, accelerated electro-thermal ageing is employed to age the cables for 10 and 20 days, with a particular focus on the impact of electro-ageing on the performance of aircraft cable insulation under diverse overload current conditions. The ageing-induced changes in thermal stability, chemical structure and microstructure were characterized using thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Additionally, the remaining lifespan of the cables after ageing is assessed. The results demonstrate that the ageing process results in a reduction in the activation energy of the material, from 333.17 kJ mol−1 in the absence of ageing to 298.16 kJ mol−1 after 10 days of ageing and 223.22 kJ mol−1 after 20 days of ageing. This is accompanied by a notable decline in thermal stability. The molecular structure is primarily influenced by the deterioration of the C–F bond within the PTFE molecule, which undergoes a reaction with oxygen to form a C=O bond. Additionally, the microstructure of the inner surface of the insulating layer exhibits a notable increase in the prevalence of cracks. The ageing life also exhibits a considerable reduction.