3 research outputs found
An investigation into the behaviour of fibre reinforced natural gas powered vechicle (NGV) pressure cylinders under impact loading
Phd ThesisCommonly encountered accidental impact, e.g. due to roadway stone hitting, is detrimental
not only because it can produce apparent surface defects, but also because barely visible
impact damage (BVID) can be induced inside the material, which is not easy to detect by
routine inspection. Reliable prediction of the amount of damage of this type induced under
known service conditions is particularly important. Therefore, this type of impact was
chosen as the focus of the present investigation.
A combination of experimental techniques and finite element modelling was used to explore
the behaviour of a fibre reinforced natural gas powered vehicle (NGV) pressure cylinder
subjected to a low energy impact.
In order to identify the modes of failure and understand the structural response, quasi-static
indentation tests were carried out on sections of composite pipes and of a composite
pressure cylinder. Delamination and matrix cracking were established to be the two major
failure modes induced by indentation. Experimental findings were used as a basis for
assessing the validity of the modelling approach.
Thick shell and three dimensional finite element models were developed using PAFEC, a
general purpose finite element code for dynamic and static analysis. It established that the
composite pressure cylinder under this type of impact behaves quasi-statically, i.e. the
impact phenomenon predominately excites low frequency response. Repeated impact was
considered in order to extend the study to include the impact behaviour of a cylinder with pre-existing damage. It was found that a bulging effect was produced in the pressure
cylinder at the impact site, where a weak spot was created due to fibre breakage.
A fully three dimensional finite element model with static analysis was developed to
investigate the damage and material degradation during the BVID phenomenon. The
contact pressure distribution based on the Hertzian contact' relationship was applied.
Failure mode identification criteria proposed by Hashin (1980) and Chang and Springer
(1986) were used to establish the mode and extent of damage in the composite cylinder
under quasi-static loading. The predicted failure modes agreed well with the experimental results.
Finally, the present study sets out the methodology allowing systematic design of structures
having optimal impact tolerance. Based on the findings of this project, suggestions for the improvement of impact resistance of NGV cylinders were given in Chapters ix.ORS Awards:
British Gas Plc.
Clemson Catalog, 1980-1981, Volume 55
https://tigerprints.clemson.edu/clemson_catalog/1135/thumbnail.jp
Clemson Catalog, 1978-1979, Volume 53
https://tigerprints.clemson.edu/clemson_catalog/1133/thumbnail.jp