Numerical-Experimental Analysis of CFRP Specimen under Multi-Directional Thermo-Mechanical Loading

Abstract

Sustainable aviation demands alternative propulsion system, such as Liquid Hydrogen (LH2). LH2needs to be cryogenically stored in large, lightweight fuel tanks. Carbon-Fibre Reinforced Polymer (CFRP) composite tanks offer promising weight-savings. Liner-less composite tanks are prone to safety-critical issues such as leakage. Leakage is caused by the presence of microcrack networks in the laminate. It is known that these crack networks arise due to thermo-mechanical loads. Element level testing is required to build a foundational understanding of the damage and leakage phenomena. The bulge test rig is capable of such element level testing, by mimicking the multi-axial loads experienced by the tank structure at cryogenic temperature. A digital twin is developed to provide deeper insights into the behaviour of the test rig and specimen. The validity of this digital twin is quantified by a 'multi-sensor' experimental campaign. The validation dataset is obtained on a range of test configurations, both at room and cryogenic temperature. Specifically, strain data is acquired using strain gauges, fibre-optic sensors and digital image correlation. Qualitative damage assessment of post-mortem specimen is conducted using ultrasound and optical microscopy, to compare the inter and intra-laminar damage initiation predictions of the digital twin. The experimental-numerical analysis of the work is envisioned to contribute to a more representative design of bulge test specimen.