Internal fixation for bone fractures with rigid metallic plates, screws and pins is a proven operative technique. However, refracture's have been observed after rigid internal fixation with metal plates and plate fixation has been known to cause localised osteopenia under and near the plate. In the present study, resorbable composites comprising a PLA matrix reinforced with iron doped phosphate glass fibres were investigated. Non-woven random mat laminates of approximately 30% and 45% fibre volume fraction (V(f)) were produced, along with unidirectional and 0°-90° samples of approximately 20% V(f). The non-woven composite laminates achieved maximum values of 10 GPa modulus and 120 MPa strength. The 0-90º samples showed unexpectedly low strengths close to matrix value (~50 MPa) although with a modulus of 7 GPa. The UD specimens exhibited values of 130 MPa and 11.5 GPa for strength and modulus respectively. All the modulus values observed were close to that expected from the rule of mixtures. Samples immersed in deionised water at 37°C revealed rapid mechanical property loss, more so for the UD and 0-90º samples. It was suggested that continuous fibres wicked the degradation media into the composite plates which sped up the deterioration of the fibre-matrix interface. The effect was less pronounced in the non-woven random mat laminates due to the discontinuous arrangement of fibres within the composite, making it less prone to wicking. Random mat composites revealed a higher mass loss than the UD and 0°-90° specimens, it was suggested this was due to the higher fibre volume fractions of these composites and SEM studies revealed voidage around the fibres by day 3. Studies of pH of the degradation media showed similar profiles for all the composites investigated. An initial decrease in pH was attributed to the release of phosphate ions into solution followed by a gradual return back to neutral.

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SHM methods for damage detection and localization in plate-like structures have typically relied on signal postprocessing techniques applied to ultrasonic guided-waves. The time of flight is one of these signals features which has been extensively used by the SHM community for damage localization. One approach for obtaining the time of flight is by applying a particular time-frequency transform to capture the frequency and energy content of the wave at each instant of time. To this end, the selection of a suitable methodology for time-frequency transform among the many candidates available in the literature has typically relied on experience, or simply based on considerations about computational efficiency. In this paper, a full probabilistic method based on the Bayesian inverse problem is proposed to rigorously provide a robust estimate of the time of flight for each sensor independently. Then, the robust prediction is introduced as an input to the Bayesian inverse problem of damage localization. The results reveal that the proposed methodology is able to efficiently reconstruct the damage localization within a metallic plate without the need to assume a specific a priori time-frequency transform model.

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This report outlines the initial synthesis, degradation, and short-term biocompatibility of sodium phosphate glasses, for use in the drawing of fibers and manufacture of biodegradable composites. Biocompatibility studies were performed using a macrophage cell line and primary human craniofacial osteoblasts. Sodium hydrogen phosphate and sodium dihydrogen phosphate glass synthesized for less than 1 h, resulted in a higher degradation rate than glass synthesized for 3 h or more (0.015 mg cm(-2) h(-1)). Glasses with high and low ratios of hydrogen phosphate to dihydrogen phosphate had very similar degradation rates. A condensation route for the formation of the glass should give rise to varying degradation rates with varying ratios of starting materials. It is suggested that the degradation rate of the glass is independent of the concentrations of the initial reagents and that ring-opening polymerization, which reaches an equilibrium state, occurs. Biocompatibility studies suggest minimal macrophage activation (low levels of peroxide and interleukin-1beta release and rounded morphology) and high osteoblast biocompatibility. The ultimate aim of our studies is to produce a biocompatible soluble phosphate glass that can be drawn into fibers for incorporation into a polycaprolactone matrix for craniofacial bone repair. This report demonstrates the successful production of a soluble glass, which is biocompatible with regard to osteoblasts and macrophages. Recent data from our laboratory have demonstrated successful fiber drawing and production of a novel polycaprolactone.