The use of polymers in orthopaedics is steadily increasing. In some markets, such as spinal fusion and soft tissue anchors, the polymer polyetheretherketone (PEEK) is already the material of choice in the majority of implants. Despite PEEK’s widespread use, it is often associated with poor osseointegration, which can lead to implant loosening and ultimately failure of the device. Many attempts have been explored to improve the osseointegration of PEEK but none have had widespread clinical success. In this dissertation, a novel surface porous structure has been created, where limiting the porosity to the surface maintains adequate mechanical properties for load bearing applications while providing a surface for improved osseointegration. Careful control of the processing parameters resulted in tunable porous microstructures optimized for bone ingrowth: highly interconnected 200-500µm pores with porosity ranging from 60-85% and pore layers from 300-6000µm thick. Mechanical characterization, including monotonic tensile and compression, tensile fatigue, shear, and abrasion tests, were used to probe the effects of the surface porosity on the relevant mechanical properties of the material. In addition, the effect of surface porosity and surface roughness on the mechanical properties of a range of thermoplastics with varying chemistries and crystallinities was explored. This research showed that there is a great disparity in the notch sensitivity of polymers that correlates to the polymers fracture toughness as well as trends in the monotonic stress-strain curve. The results illustrate that care must be taken in the design of polymeric implants, especially when introducing topographical changes to promote osseointegration, in order to ensure they maintain adequate load-bearing capacity. Finally, preliminary in vitro and in vivo data demonstrated the ability of surface porous PEEK (PEEK-SP) to promote osseointegration. Cells grown on PEEK-SP demonstrated enhanced mineralization and differentiation, suggesting the ability of PEEK-SP to facilitate bone ingrowth. The potential of PEEK-SP was further demonstrated by implantation in a rat femoral segmental defect model which demonstrated bone ingrowth and reduced formation of a fibrous capsule.

This thesis presents the experimental and analytical results to investigate the effect of corrosion on the mechanical properties of reinforcing bars and concrete beams, with particular reference to their ductility. In the experimental works, specimens were electrochemically corroded, before they were loaded to failure. In the finite element analysis, the corrosion of reinforcement was modelled as either internal pressure or radial expansion around corroded bars. The study indicates that the amount of corrosion to cause cracking at the bar and concrete surfaces almost linearly increased with the bar diameter and ratio of cover to diameter, respectively. No matter whether concrete cover c increased or bar distance S decreased, once the ratio of S / c became less than 2.5, corrosion cracks first propagated internally between the bars and caused delamination. Although corrosion did not alter the shape of force-extension curves substantially, it decreased bar strength and, especially, ductility greatly. Furthermore, although the reductions of strengths were identical, the ductility of bars corroded in concrete decreased more rapidly than that of bare corroded bars. Corrosion decreased beam strength and altered its ductility and failure mode. When the cracking of compressive concrete or the reduction of tensile bar area dominated beam response, corrosion increased beam ductility and caused a beam to fail in a less brittle and even ductile manner. When the deterioration of bond strength or the reduction of steel ductility controlled beam behaviour, however, corrosion decreased beam ductility and led the beam to fail in a less ductile and even brittle manner. There is a concern regarding the ductility of reinforcing bars and under-reinforced beams if the amount of corrosion exceeds 100/0, since bar ultimate strain decreased below the minimum requirements prescribed in the Model Code 90 for situations requiring high ductility.

Background: Strength and power are important factors in many sports, and rotational power of the trunk and upper body are important components of golf performance. Trunk and pelvis cooperated in the rotation movement and strength in the muscles surrounding these segments is contributing to a successful and powerful rotation. Side-to-side asymmetry is often discussed in the field of injury prevention and it is suggested that bilateral imbalances affects the performance. Hand strength is a measure of diverse use when testing physical requirements in athletes. It has previously been concluded that hands strength correlates strongly with strength in both lower and upper extremity in youths, but the correlation among adults and athletes are unknown. In golf, hand strength has been stated to be one of the most important components for golf performance and it strongly correlates with golf specific variables such as ball speed and drivers distance. The relationship between hand strength and rotational power is unknown. Aim: The aim was to study rotational peak power and hand strength in young golf players to compare side-to-side differences and the relationship between rotational peak power and hand strength. Methods: Twenty-seven subjects, 22 men and 5 women, with a golf handicap of ≤5 participated in the study. The two tests performed was a hand strength test using a T.K.K handheld dynamometer and a rotational peak power test in Quantum. The tests were performed at the same session, first hand strength and then rotational peak power. In order to test the rotational peak power a 1RM test was performed. In order to study the relationship between hand strength and rotational power a Spearman´s range of correlation (rs) was used. A Wilcoxon signed-ranked test was used to study the side-to-side differences between dominant and non-dominant hand strength and rotational power. Results: No statistical significant differences were found between dominant and non-dominant hand strength (p = 0.28) or between dominant and non-dominant rotational power (p = 0.97). A strong correlation between dominant hand strength and dominant rotational power was found (rs = 0.636) and a moderate correlation between non-dominant hand strength and non-dominant rotational power (rs = 0.589). Conclusion: There are no side-to-side differences in hand strength or rotational power in young healthy golf players. Dominant hand strength correlates strongly with dominant rotational power.

No description available.

published_or_final_version / Sports Science / Master / Master of Science in Sports Science

published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.