104 - ELECTRICAL MEASURMENTS FOR CRACK LENGTH MEASURMENT IN FIBRE REINFORCED POLYMERS (CompTest 2025)
Due to their outstanding mechanical properties, fibre composites already have a wide range of applications in the mobility sector. With the transition of the economy away from fossil fuels towards renewable energies, hydrogen is set to play a central role in many applications. Concepts are currently being developed to power aircraft or lorries with hydrogen. This requires tanks made of lightweight materials that meet the high requirements of the mobility sector. Due to its comparatively high energy density, liquid hydrogen is to be used as an energy carrier in aviation [1]. However, this must be stored at - 253°C, which places enormous demands on the tank and its insulation. When a liquid hydrogen tank is filled, the tank walls cool down very quickly. Tanks made of carbon fibre reinforced plastics (CFRP) are subject to high thermal stresses during cooling. The brittle fracture behaviour of the epoxy matrix, which is exacerbated by low temperatures, results in microcracks in the matrix [2]. The microcracks accumulate in the material over the number of cooling and heating cycles. If a continuous path has been created through the tank wall, the hydrogen can penetrate from the inside to the outside and deteriorate the vacuum insulation of the tank. This leads to so-called boil-off losses and a poorer storage capability of the hydrogen in the tank. One way to prevent microcracks in the matrix is to increase the fracture toughness of the matrix. A high fracture toughness requires a higher energy and therefore a higher load to cause cracks to form or grow in the material. Common systems for increasing fracture toughness are toughening modifiers or flexibilisers made from thermoplastic polymers or elastomers, which extend the path of a crack by adding a second phase to the matrix. For use in a hydrogen tank, these systems must also lead to an increase in toughness at low temperatures in order to prevent thermally induced cracks. This work focuses on the development of toughening modifiers to increase the fracture toughness of the matrix, which can also be used at low temperatures. For this purpose, chemical toughening modifiers and carbon nanoparticles are added to the resin as additives and processed together with glass fibres in an impregnating roller mill to form prepreg material. The material is cured in an autoclave and specimens for double-cantilever beam (DCB) and end-notched fibre (ENF) tests are cut from the sheets.
Pieteikuma datums
21.05.2025.
Atslēgas vārdi
Mode I, DCB Test, Mode II, ENF Test, Capacitance, FRP
