Browsing by Author "Von Klemperer, Christopher Julian."

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Accelerated environmental degradation of GRP composite materials.
(2004) Dlamini, Power Madoda.; Von Klemperer, Christopher Julian.; Verijenko, Viktor.
The use of fibre reinforced polymer composites and development of structural composites has expanded rapidly in the Southern African region over the past ten years. The long-term effect of placing these materials outdoors in the Southern African climate is unknown with exposure data for these materials being primarily European and North American based. This study intends to take a broad-based study to the problem of environmental degradation of advanced composite structures. This work is intended to study different degradation mechanisms. Work performed includes: a study of literature on degradation and protective measures; identification of dominant degradation mechanisms; manufacture of specimens; accelerated environmental testing; and an assessment of the effect of the exposure on the chemical properties The goal of this work is to produce information, which can be subsequently used to determine the rate of damage, methods of suitable protection and necessary maintenance intervals for polymer composite components. The approach was: to simulate outdoor exposure within a reduced period of time; to establish correlation of results with actual outdoor exposure; and to determine how the gel coats compare with other protective methods. As part of the objectives of the study (i.e. to assess the durability of polymer matrix composites materials subjected to environmental exposure), an experimental study was carried out to establish the durability of specific gel coats against ultraviolet (DV) and moisture degradation. An investigation of the effectiveness of the various protective measures has begun with a review of selected gel coats available as a protective coating. Laminates with these gel coats have been set up for both accelerated and natural exposure tests. 3000, 2500, 2000, 1600, and 800 hours of accelerated DV exposure tests were performed on polyester GRP laminates with gel coats. No measurable strength loss occurred on protected laminates; there was significant increase in yellowness on un-protected laminates; all protected specimens showed a fair retention of gloss; fibre prominence occurred on unprotected laminates; and the glass transition of samples had dropped from the normal polyester glass transition temperature range.
A comparative study on the effects of internal vs external pressure for a pressure vessel subjected to piping loads at the shell-to-nozzle junction.
(2003) Maharaj, Ashveer.; Adali, Sarp.; Von Klemperer, Christopher Julian.
This investigation seeks to perform a comparative study between the combined effects of internal pressure and piping loads versus external pressure and piping loads on a pressure vessel. There are currently several well-known and widely-used procedures for predicting the stress situation and the structural stability of pressure vessels under internal pressure when external piping loads (due to thermal expansion, weight, pressure, etc.) are applied at the nozzles. This project familiarises one with several international pressure vessel design Codes and standards, including AS ME (American Society of Mechanical Engineers) pressure vessel code sections and WRC (Welding Research Council) bulletins. It has been found that many vessels are designed to operate under normal or steam-out conditions (in vacuum). The combined effect of the external atmospheric pressure and the piping loads at the nozzle could be catastrophic if not addressed properly - especially when the stability of the structure is a crucial consideration, i.e. when buckling is a concern. The above-mentioned codes and standards do not directly address procedures or provide acceptance criteria for external loads during vacuum conditions. The approach to the study was, firstly, to investigate the effects of internal pressure and piping loads at the shell-to-nozzle junction. Theoretical stresses were compared with Finite Element results generated using the software package MSC PATRAN. Finite Element Methods provide a more realistic approach to the design of pressure vessels as compared to theoretical methods. It was necessary to determine if the theoretical procedures currently used were adequate in predicting the structural situation of a pressure vessel. Secondly, the buckling effects of vessels subjected to external atmospheric pressure and piping loads were also investigated. Buckling of the shell-to-nozzle region was explored with the aid of Finite Element software. The results gained were used to develop appropriate procedures for the design of vessels under external atmospheric pressure and piping loads. The design is such that it indicates if buckling will occur at the shell-to-nozzle junction. These design procedures form the basis for future exploration in this regard.
Optimisation of the process parameters of the resin film infusion process.
(1999) Von Klemperer, Christopher Julian.; Verijenko, Viktor.
The resin film infusion process or RFI is a vacuum assisted moulding method for producing high quality fibre reinforced components. The goals of this research have been to investigate this new process, with the aim of determining how the process could be used by the South African composites industry. This included factors such as suitable materials systems, and optimum process parameters. The RFI process is a new composite moulding method designed to allow fibre reinforced products to be manufactured with the ease of pre-preg materials while still allowing any dry reinforcement material to be used. The high pressures required for traditional manufacturing methods such as autoclaves, matched dies and R TM can be avoided while still having very accurate control over the fibre / resin ratio. Moreover, the RFI process is a "dry" process and hence avoids many of the environmental and health concerns associated with wet lay-up and vacuum bag techniques. Furthermore the simple lay-up process requires less skill than a wet lay-up and vacuum bag method. Through a combination of mathematical modelling and physical testing, a material system has been identified. The primary process parameters were identified and a strenuous regime of testing was performed to find optimum values of these parameters. These results were finally feed back into the development of the mathematical model.