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A previous study, looking at the creep-rupture behaviour of mixed reinforcement GRP when immersed in water, had discovered that low loads, behaviour became temperature sensitive. Since the recorded time to failure of a sample was reduced at elevated temperatures, from that predicted by a linear extrapolation of the short term creep-rupture results, this deviation caused problems in the accurate prediction of long-term design stresses. In order to improve the accuracy of long term design predictions, it was decided to study the mechanisms of creep in GRP that initiates time dependent failure. From this, it was hoped that accurate design criteria suitable for predicting GRP response over a 30 year design life from short term creep tests, could be developed. This thesis reports the results obtained from such a study. A series of creep tests were performed on mixed reinforcement GRP samples at several stress levels, both in air, and in room temperature distilled water, using a microcomputer based data collection system. In conjunction with this work, damage development in samples, due to combinations of water uptake and creep loading, was followed, using both scanning electron, and optical, microscopy. Moisture uptake measurements were undertaken under a series of load/temperature regimes, and fibre/matrix debonding followed using photographic techniques. In this way, water absorption, both in terms of uptake rate, and location within a sample, could be characterised. Tensile tests were also performed to determine the standard mechanical properties of the mixed reinforcement GRP used. It was found that a critical damage state was created at loads in excess of 50% of ultimate, but not below. This took the form of between 2 and 8 neighbouring filament breaks in the longitudinal woven rovings at weave crossover points, producing microcracks in the reinforcement. The creation of this multifilament fracture damage during primary creep, was considered to be necessary for time dependent failure to occur in air. Secondary greep strain was found to increase in discrete steps, both in air and water. This was attributed to the formation of transverse grasks in the longitudinal woven rovings, propogating from the above critical damage. In water, diffusion was found to be non-Fickian. Moisture uptake increased with increases in applied load and temperature. Water was seen to accumulate at weave cross-over points when immersed under load. This led to stress-enhanced fibre corrosion in these regions, weakening the reinforcement, and reducing the failure time from that expected at the same load level in air. The localised nature of moisture degradation was thought to result in the formation of critical fibre damage at loads below 50% of ultimate, when immersed in water. Two design criteria based on the observed creep mechanisms, have been developed for GRP that predict response when loaded in either air, or water. Both predict the existence of creep-rupture limits at low loads.

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This thesis examined the feasibility of fibre composite reinforcement in the furniture industry. The development of post war furniture design was reviewed, with particular emphasis on the main design movements and the use of new materials and technologies. The use of fibre composite materials in contemporary furniture was discussed in terms of technical development, environmental effects and psychological acceptance. Fibre reinforcements and adhesives were compared, as were fabrication techniques applicable to the existing British furniture industry. Particular emphasis has been placed on the fibre reinforcement of laminated timber sections as a method of overcoming many of the manufacturing problems of composites. Methods of analysing the behaviour under load of fibre reinforced laminated wood were reviewed. Resistance among the furniture buying public to modem, non-traditional furniture design was discussed, along with ways of making composite materials more aesthetically acceptable. Experimentation to determine the mechanical properties of fibre composite reinforced wood against wood control samples was undertaken, along with methods used to analyse the results for flat and curved samples. Modulus of elasticity, modulus of rupture and impact strength were measured, as was the level of distortion of the samples before and after testing. A full size chair form was produced to demonstrate the behaviour of the material on a larger scale. The development of the design was discussed in terms of ergonomic requirements, aesthetics, practicality and environmental concerns. The problem of predicting the behaviour of complex shapes was discussed and a finite element analysis of the form is carried out to gain an accurate picture of the composite's performance. Production of fibre reinforced materials was discussed, along with the furniture industry's reluctance to invest in new materials and technologies. The feasibility of adapting traditional furniture making skills and equipment to the production of fibre composite reinforced wood has been assessed.

This research was conducted to better understand the corrosion propagation stage on dry-cast reinforced concrete pipes (DCRCPs) while exposed to high moisture conditions and chlorides. Corrosion initiation and propagation were studied in instrumented specimens obtained from segments of dry-cast reinforced concrete pipes. All specimens were subjected to accelerated chloride transport by the application of an electric field. Corrosion of the steel wire mesh initiated after a few days to a few months rather than several years. The specimens were then transferred to high moisture environments (immersed in water, high humidity and/or covered with wet sand) during the corrosion propagation stage. Reinforcement potentials, linear polarization resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS) measurements were carried out periodically. During the propagation stage in different exposures, reinforcement eventually reached negative potentials values (< –-0.55 Vsce), which suggest mass transfer limitations. These specimens showed no visual signs of corrosion such as cracks or corrosion products except the ones exposed to high humidity and laboratory environments; where some corrosion products have reached the concrete surface. Moreover, the apparent corrosion rate values obtained suggest high corrosion rates. No crack appearance on specimens exposed to other conditions could be explained by the porosity of the specimens; the corrosion products moved into saturated pores. It is speculated that although there might be mass transfer limitations present, the current demanded by the anode is being balanced by a larger cathode area due to macrocell effects since the high moisture conditions likely reduced the concrete resistivity and increased the throwing power. The corrected polarization resistance (Rc) was calculated by subtracting the solution resistance from the apparent polarization resistance measured. The Rc values measured over time were used to obtain the calculated mass loss (using Faraday’s Law). Most specimens were forensically analyzed and the measured mass loss compared to the calculated mass loss. The forensic examination includes the measurement of the actual corroding areas. The measured corroding areas were used to obtain corrosion current density (icorr) values. A comparison was made of the calculated corrosion current densities obtained using the linear polarization resistance method (LPR) and the extrapolation method from cyclic polarization tests. It was evident that most of the specimens’ corrosion rates were significantly high. The corrosion products filled the wet-pores inside the concrete and provide an explanation for no cracks or corrosion bleed outs being visually observed on the specimens. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

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