Investigation Of The Mechanical Properties Of Carbon And Glass Fibres Exposed To Cryogenic Temperatures And Cryogenic Cycling
Topic(s) : Special Sessions
Co-authors :
Lewis KELLY (UNITED KINGDOM), Liu YANG , John LIGGAT , Ross MINTYAbstract :
A variety of industries are currently exploring the potential utilization of liquid hydrogen (LH2) as a pivotal energy source for the future. Given the market impetus for wide adoption of LH2 there is a significant need to establish rational design rules for the pressurised vessels that will be used to store LH2 safely [1]. These vessels, manufactured using composite materials, will be exposed to long-term adverse environmental conditions that have not yet been fully investigated. The effect of cryogenic cycling on the fundamental fibre-matrix performance of a composite material is an unaddressed and critical parameter in the long-term structural performance of LH2 pressurised vessels.
Composite properties arise from an amalgamation of the characteristics of the fibre and the matrix alongside the ability to transfer stresses across the fibre-matrix interface [2]. The strength of the fibre-matrix interface determines the extent to which applied stress can be transferred to the load-bearing fibres. This interfacial strength is largely determined by the degree to which the fibres and matrix are intimately contacted and the level of adhesion at those contact points.
Given the pivotal role of the fibre-matrix interface in defining the long-term performance of composites deployed in harsh environments, there is now an important need for fundamental studies of the effects that repeated exposure of a composite system to cryogenic conditions will have on the fibre-matrix interface [3]. This in turn will inform us of any changes to the structural and sealing performance of a composite pressurised vessel used to store LH2 [4]. There is a critical need to understand and optimise the interface interaction for current and next generation resin systems, considering the harsh operating environments they are expected to endure in the long term.
However, prior to this it is first necessary to understand the effects on the mechanical properties of single fibres that materialise after exposure to cryogenic conditions. Currently there has been a reasonable amount of research into the material properties of the fibres whilst under cryogenic conditions [3, 5, 6] but none have investigated the effect of cryogenic cycling. Given the scale and nature of the testing to be conducted, and its sensitivity to changes in material property, at either a fibre or interface level, it is thus essential to gain an understanding of the characteristics and trends that will vary solely in individual fibres prior to investigating the changes to the fibre-matrix interface collectively.
Therefore, in the present work the impact of cryogenic shock and cryogenic cycling on the mechanical properties of individual carbon and glass fibres was investigated with subsequent analysis of the fibre surface using scanning electron microscopy. Subsequently, this will serve as a prerequisite for further investigations into the fibre-matrix interface.
Composite properties arise from an amalgamation of the characteristics of the fibre and the matrix alongside the ability to transfer stresses across the fibre-matrix interface [2]. The strength of the fibre-matrix interface determines the extent to which applied stress can be transferred to the load-bearing fibres. This interfacial strength is largely determined by the degree to which the fibres and matrix are intimately contacted and the level of adhesion at those contact points.
Given the pivotal role of the fibre-matrix interface in defining the long-term performance of composites deployed in harsh environments, there is now an important need for fundamental studies of the effects that repeated exposure of a composite system to cryogenic conditions will have on the fibre-matrix interface [3]. This in turn will inform us of any changes to the structural and sealing performance of a composite pressurised vessel used to store LH2 [4]. There is a critical need to understand and optimise the interface interaction for current and next generation resin systems, considering the harsh operating environments they are expected to endure in the long term.
However, prior to this it is first necessary to understand the effects on the mechanical properties of single fibres that materialise after exposure to cryogenic conditions. Currently there has been a reasonable amount of research into the material properties of the fibres whilst under cryogenic conditions [3, 5, 6] but none have investigated the effect of cryogenic cycling. Given the scale and nature of the testing to be conducted, and its sensitivity to changes in material property, at either a fibre or interface level, it is thus essential to gain an understanding of the characteristics and trends that will vary solely in individual fibres prior to investigating the changes to the fibre-matrix interface collectively.
Therefore, in the present work the impact of cryogenic shock and cryogenic cycling on the mechanical properties of individual carbon and glass fibres was investigated with subsequent analysis of the fibre surface using scanning electron microscopy. Subsequently, this will serve as a prerequisite for further investigations into the fibre-matrix interface.