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The present studies are concerned with the modelling of the manufacturing process of nitrocellulose-base propellant in which cellulose acetate is substituted as a model for the explosive nitrocellulose. An investigation of the inter-relationships between processing and rheological and morphological properties has been carried out on cellulose acetate doughs, using modified torque and capillary extrusion rheometers. Some of the doughs show a yield stress and behave as Herschel-Bulkley fluids. The yield stress is found to be smaller than that of nitrocellulose doughs, and there is some evidence of shear heating. Mixing time and mixing temperature showed no influence on the rheological parameters of the doughs. These results suggest that the change in rheological properties of propellant doughs is attributed to the change in crystallinity and fibrosity after processing. The rheological properties of doughs are greatly affected by extrusion temperature, solvent, plasticiser and filler content. The interaction between the solvents and plasticisers with cellulose acetate was explained by adopting a model consisting of a rigid backbone chain from which protruded flexible side groups. In good solvents these side groups extend causing interactions between molecules, giving rise to dough up and elasticity. In poor solvents, dough up becomes difficult and the elasticity is low because the flexible side groups retract towards the stiff backbone chain. The morphology of solvated doughs is examined using solution viscometry, infrared spectroscopy, scanning electron microscope, differential scanning calorimetry, x-ray diffraction and dynamic mechanical thermal analysis. All these techniques showed that the solvation process had no significant effect on the molecular architecture of the cellulose acetate, in which the original crystallinity of the material is low. From this it was concluded that changes in the rheological properties of nitrocellulose doughs as a function of the process variables was due to changes induced in the crystallites rather than in the amorphous regions.

Jets resulting from shaped charges which contain metal liners are able to penetrate hard or armoured targets. Their penetration performance is related to the density of the jet and target material and also the length to which the jet can elongate. Models that describe the processes involved have generally assumed hydrodynamic fluid flow and as such have been very successful in most cases. However, the break-up of jets has proved to be inconsistent with the fluid flow models and cannot be accurately described. Break-up is important since it is the final phenomenon in tensile deformation and therefore represents the limiting extent of jet elongation. Additionally, following break-up the jet fragments are particularly susceptible to lateral velocities and tumbling which dissipate the jets energy and further reduce its penetration performance. Research by Hunting Engineering Limited has indicated that mechanical properties are related to the jet break-up phenomena. However, the deformation and break-up of shaped charge jets is not well understood from a metallurgical point of view. It is essential that the jet is in the solid state for jet break-up phenomena to be related to the mechanical properties of the liner material. This has been demonstrated here by theoretical analysis and more directly by observation of in-flight and captured jet fragments. A series of experiments have been carried out in order to measure and analyse the deformation and attempt to put forward models for the break-up mechanisms in shaped charge jets. These were based upon a series of selected aluminium and aluminium alloys which were processed and heat treated to produce a range of mechanical properties. The properties under consideration are those which describe the materials strength, elongation and work hardening characteristics at intermediate strain rates under laboratory conditions. These have been used to relate metallurgical details to the nature of jet break-up. The better materials for shaped charge jets would appear to be high purity metals which exhibit large ductility through to fracture.

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This thesis examines the technology used for tools and equipment for humanitarian landmine clearance. The main focus is on the removal of mine and unxeploded ordnance contamination in the poor, heavily mined countries, particularly Afghanistan and Cambodia. Initially, the process of humanitarian demining in these countries was examined and described, and the relevant literature reviewed. Three studies were undertaken with a dual purpose of (a) providing relevant contributions to the science of mine clearance and (b) evaluating some of the methods commonly used in humanitarian demining research. (i) A statistical analysis of the evaluation of mine detection systems in trials was undertaken. This demonstrated that (a) this statistical analysis is straightforward, and (b) feasible sized trials do not yield useful results from analysis of the crude minedetection rate. An enhancement to the evaluation process, "Margin of Detection," was suggested. (ii) Research into improved "prodders" for detecting mines was undertaken with as much consultation with deminers as possible early in the research cycle. "Sensing prodders" were shown to function technically but not to improve the overall demining process. Measurements showed that many deminers prod in hard soils with suÆcient force to detonate some mines; rotary prodders were developed to reduce the force required for excavation, but success in the laboratory could not be duplicated in eld conditions. From this work a potentially useful tool for deminer training was developed, which might reduce the risks of accidental detonation. (iii) The limits of a high-tech detection technique (neutron irradiation and detection of prompt gamma rays) were examined (a) to advance understanding of this method and (b) to demonstrate the feasibility of early evaluation of technologies before extensive research is started. This neutron technology was shown to oer potential benets to military demining, but to be unlikely to have general application when the higher clearance standards and lower equipment budgets of humanitarian demining were applied. The thesis ends with conclusions and suggestions for some further work. Throughout the thesis, the research is focussed on investigating practical problems which deminers have suggested as important constraints on their work.