A METHODOLOGY FOR THE CONTROL OF THE RESIDUAL LIFETIMES OF CARBON FIBRE REINFORCED COMPOSITE PRESSURE VESSELS

摘要

Pressure vessels must be periodically proof tested. Traditional techniques for metal vessels are inapplicable for composite vessels as the latter do not break by crack propagation so that the reasoning behind the traditional testing procedures is not appropriate. Damage accumulation leading to the degradation of a composite vessel is by fibre failure. Fibres show a wide distribution in strengths and loading a composite inevitably breaks some. The method which has been developed is supported by an analysis of delayed fibre failure due to the relaxation of the resin around fibre breaks. This provokes overloading of intact fibres neighbouring breaks. The time until a critical density of breaks is reached can be calculated at which point the pressure vessel is deemed unstable. The test can be applied to pressure vessels which have been used in service and it is not necessary to know the details of their loading history with precision.