Crack analysis in CFRP by means of fiber optical sensors

Kurzfassung

Sustainable aviation requires radical new thinking in aircraft design. One pillar is the transition from fossil to hydrogen combustion and fuel-cell powertrain systems. Therein, storage of liquid hydrogen poses a great challenge due to cryogenic temperatures. Tanks made from CFRP exhibit great weight- and cost-saving potentials. However, CFRP is prone to microcrack and crack-network formation resulting in leakage. The ability to monitor the crack density in CFRP structures during operation could offer a great benefit. Thus, application of Fiber-Bragg-Grating (FBG) sensors within CFRP laminates for analysis of the crack density is investigated. It is observed that thermal strain measurements by FBG sensors correlate with the microcrack density determined using optical microscopy after thermal and mechanical cycling of specimens. Both parameters are assumed to be interlinked through the mean coefficient of thermal expansion of the laminate. The results are promising regarding an application of FBG-sensors for the development of CFRP tanks as well as during in-flight operations.