This thesis deals with the determination of the effect of controlled relative humidity (RH) on the mechanical properties of coil coatings. The coil coatings studied were based on polyester/melamine technology. The study employed mechanical and dynamic mechanical analysis, using modified environmental chambers, to measure the effects of controlled RH on a range of mechanical parameters. Of particular interest was the effect of controlled RH on the minimum forming temperature of the coil coated metallic panels. This is the temperature below which the coating would fracture. A description has been given of the modifications made to both a mechanical tester and a Dynamic Mechanical Analyser (DMA), which allowed controlled RH experiments to be performed under isothermal or thermal scanning conditions. Comparison of this study with published work showed that some experimental data in the literature could be erroneous due to lack of, or inappropriate, RH conditioning prior to testing. The results showed a good correlation for both free film and coated metal samples between the glass transition temperature (Tg) and the brittle-tough transition (Tbt). A reduction of both the Tg and the Tbt of up to 15°C were found as the controlled RH was increased. A controlled RH and environmentally instrumented slow-draw cupping device was constructed to measure the behaviour of coil coatings on aluminium (Al) and hot dip galvanised steel (HDG-steel) substrates. The importance of indentation depth during the cupping test and the difference between the substrates was emphasised. Fracture mechanics was employed to study differences in performance.

No description available.

The low velocity impact, tension-tension fatigue and stress relaxation behaviour of glass fibre and natural fibre composites were investigated. For glass fibre composites, two fibre architectures ([±45^o]₄ and [0/90^o]_2s) and two matrix resins (polyvinyl-ester and polyester) were used. Non-woven randomly oriented hemp fibre mat was used as reinforcement of natural fibre composites. The effects of low velocity impact on residual tensile properties, fatigue life and modulus degradation behaviour during cyclic loading were investigated. Damage mechanisms of the composites during impact and fatigue loading were discussed. It was found that modulus degradation behaviour of composites was strongly dependent on the reinforcing fibres and their architecture. Multistage modulus degradation behaviour with gradual reduction in modulus was observed during fatigue loading of [±45^o]₄ glass fibre composites. For hemp fibre composites, however, no decrease in modulus was observed before final fatigue failure. Low velocity impact did not significantly change the modulus degradation behaviour of composites during fatigue loading. Since the normalized S-N curves for undamaged and impacted samples superimposed, the fatigue life of impact damaged composites could be predicted from knowledge of the S-N curve of non-impacted composites and the static residual strength of impact damaged composites. Stress relaxation curves of [±45^o]₄ and [0/90^o]_2s glass fibre composites were compared, and the effects of initial stress, impact damage, fatigue loading and the combination of impact and fatigue were investigated. Mechanisms of stress relaxation of composites were discussed. Stress relaxation curves of the glass fibre composites could be modelled by a simple logarithmic equation. Stress relaxation tests were found useful to characterise the loading history of composites.

The economic and technical advantages of particle filled polymer composites are a key reason in their increasing scientific and commercial importance over other engineering materials. The addition of particles to polymers has been proved to be an effective way to control their thermal, optical, and aesthetic properties. The scope of the current research is to assess the mechanical behaviour of particle reinforced solid surface composites made of alumina trihydrate filled poly (methylmethacrylate). A series of mechanical tests are performed including static fracture, flexural, and impact investigations. Microscopy studies are carried out to give an indication of the particle size and shape. The knowledge of the elastic modulus of particle filled polymers at different temperatures and filler contents is identified as a convenient way of categorising these materials. A concise methodology is developed for the measurement and prediction of the stiffness and fracture toughness of particle filled poly-methyl methacrylate.The experimental flexural modulus of the composites is found to decrease with increasing temperature (0 �°C - 90 DC) and increase with increasing particle volume fraction. Concurrent improvement of the stiffness and fracture toughness of the composites with increasing filler contents is indicated from the experimental results. The elastic behaviour of ATH-PMMA at different temperatures and filler volume fractions is fully evaluated by using a combination of experimental and theoretical modelling techniques. The Lielens, Lewis and Nielsen and the Constraint Composite (CCM) models are in excellent agreement with the experimental data. The complex deformation processes involved in the fracture of the composites are identified as the major factor associated with the difficulty in obtaining a complete understanding of the fracture behaviour of the materials. It is possible that the insight obtained through this work gives the possibility for future modelling of the fracture performance in future research.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.