Development of Continuous and Real Time Structural Health Monitoring of Aircraft Primary Structure through Embedded Carbon Nano Fiber Sensors

In this article, a new approach for structural health monitoring of aircraft primary structure has been dealt with, embedded carbon nano fiber (CNF) sensors. The multi-functional ability of non-conductive Glass Fiber Reinforced Polymers (GFRP) material is enhanced by addition of conductive CNF. An experimental investigation was carried out on bi-directional glass fiber to study the damage sensing capabilities of nano composite through embedded CNF mat-based sensor. In the study, CNF was dispersed in Poly Vinyl Alcohol (PVA) solution, and PVA-CNF sensor mat was developed by using electro-spinning process. This mat was embedded into the GFRP by using vacuum resin transfer moulding process at the design stage. CNF neither increases the weight of the composites nor affects its structural and mechanical properties. CNF sensor mat at various orientation and different wt% was embedded to the GFRP. The fabrications of specimens were done using bi-directional glass fiber with epoxy resin. Incremental tensile loading and unloading were conducted during test, and their corresponding electrical conductivity was monitored. The electrical resistance measurement of the embedded PVA-CNF mat is used to assess the structural weakness during mechanical test. Mechanical loading and the change in electrical resistance were directly correlated. Residual resistance measurements of the CNF mat were monitored during unloading condition for high stress (or strain). Accumulating damage to the composite material was calculated and correlated to the electrical resistance readings. The standard size of the coupons is 250x25x2 mm as per ASTM standard D3039.