Development of test fixtures for fiber reinforced composites at cryogenic temperatures
Topic(s) : Special Sessions
Co-authors :
Holger HÄFELE (GERMANY), Anna TRAUTH (GERMANY), Markus SAUSE (GERMANY)Abstract :
The principle of widely developed novel hydrogen propulsion concepts relies upon the safe storage of gases. Gases, characterized by their higher energy to weight ratio, can be stored either at ambient temperature, requiring a substantial storage volume due to their notably low density, or as liquified gases cooled down to very low temperatures in the cryogenic range. However, the integration of liquified gases as energy reservoirs introduces challenges regarding vessels that are suitable for both, extremely low temperatures, and high pressures at the same time. Hence, for future energy and fuel storage of liquified gases a comprehensive understanding of temperature dependent material behavior at cryogenic temperatures is required.
The presented study addresses the challenges to perform mechanical material characterization of fiber reinforced polymers exposed to very low temperatures within different concepts to create cryogenic conditions. The primary objective of this project is to develop several test configurations for the mechanical characterization of carbon fiber reinforced polymers in accordance with established standards. The fixtures are designed to ensure valid materials characterizations at both, room temperature and cryogenic conditions. Therefore, we propose test fixtures without movable components or pneumatic and hydraulic actuators.
To validate the newly designed test rigs we applied 3D digital image correlation (3D-DIC) to assess the resulting strain states. The test rigs allow improved accessibility inside the cryostats and aim for simplification of specimen handling under cryogenic conditions. The suitability of the test rigs for cryogenic conditions was validated at 77 K. We successfully implemented test fixtures encompassing quasistatic mechanical material characterization under tension, compression, and shear load. Furthermore, we introduced test fixtures for investigating fracture toughness under both, mode I and mode II loading conditions. The test setups provide a homogenous stress state within the test section of the material, which was investigated by 3D-DIC. Valid failure modes were obtained for the tested unidirectional carbon fiber reinforced polymers. In essence, the adapted test rigs expand the possibilities of the available testing methods for a valid and reproducible mechanical characterization of materials under cryogenic temperature conditions . This paves the way for improved safety when engineering pressure vessels in this application field and can be used to minimize the overall weight of the pressure vessels.
The presented study addresses the challenges to perform mechanical material characterization of fiber reinforced polymers exposed to very low temperatures within different concepts to create cryogenic conditions. The primary objective of this project is to develop several test configurations for the mechanical characterization of carbon fiber reinforced polymers in accordance with established standards. The fixtures are designed to ensure valid materials characterizations at both, room temperature and cryogenic conditions. Therefore, we propose test fixtures without movable components or pneumatic and hydraulic actuators.
To validate the newly designed test rigs we applied 3D digital image correlation (3D-DIC) to assess the resulting strain states. The test rigs allow improved accessibility inside the cryostats and aim for simplification of specimen handling under cryogenic conditions. The suitability of the test rigs for cryogenic conditions was validated at 77 K. We successfully implemented test fixtures encompassing quasistatic mechanical material characterization under tension, compression, and shear load. Furthermore, we introduced test fixtures for investigating fracture toughness under both, mode I and mode II loading conditions. The test setups provide a homogenous stress state within the test section of the material, which was investigated by 3D-DIC. Valid failure modes were obtained for the tested unidirectional carbon fiber reinforced polymers. In essence, the adapted test rigs expand the possibilities of the available testing methods for a valid and reproducible mechanical characterization of materials under cryogenic temperature conditions . This paves the way for improved safety when engineering pressure vessels in this application field and can be used to minimize the overall weight of the pressure vessels.