Browsing by Author "McGee, Christine"

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    Additively Manufactured (3DP) thermite structures vs conventionally manufactured equivalents
    (Cranfield University, 2020-01-09 10:23) McGee, Christine
    Research into additive manufacturing (AM) has been steadily expanding over the past five decades. Where once only polymeric materials could be reliably printed, AM has been adapted to print with a range of materials such as biological, metallic, ceramic and even foodstuffs. The advantages of manufacturing in an additive manner include; a) a layer-by-layer approach allows the creation of architecturally complex structures, b) a reduction in weight, c) lessening of waste and d) the ability to create parts that are otherwise difficult or too costly to produce. Pyrotechnic materials, including thermite, are used in a wide range of commercial and defence applications. However, hazards present during manufacturing and storage have resulted in major accidents around the world, with subsequent loss of life and in some cases loss of public infrastructure. AM, using a dry powder printing technique means that parts can be manufactured on demand, reducing the need for storage of large volumes of fully formed products or mixes, thus increasing the safety over lifetime of a product.The performance of pyrotechnics materials is dependent on a number of properties, including chemical composition, thermodynamic properties and physical form. In combination with composition, architecture could be utilised to understand and control these properties. A bespoke printer capable of additively manufacturing pyrotechnic materials has been constructed with the aim to explore this research area. In this paper, we discuss the development of the AM technique and methodology for the burn test experiments. We conclude with the results from the burning of AM thermite structures and compare their performance with conventionally prepared equivalent thermite examples.
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    ItemOpen Access
    Additively manufactured (3DP) thermite structures vs conventionally manufactured equivalents
    (IPSUSA Seminars, 2022-07-14) McGee, Christine; Vrcelj, Ranko
    Research into additive manufacturing (AM) has been steadily expanding over the past five decades. Where once only polymeric materials could be reliably printed, AM has been adapted to print with a range of materials such as biological, metallic, ceramic and even foodstuffs. The advantages of manufacturing in an additive manner include; a) a layer-by-layer approach allows the creation of architecturally complex structures, b) a reduction in weight, c) lessening of waste and d) the ability to create parts that that are otherwise difficult or too costly to produce. Pyrotechnic materials, including thermites, are used in a wide range of commercial and defence applications. However, hazards present during manufacturing and storage have resulted in major accidents around the world, with subsequent loss of life and in some cases loss of public infrastructure. AM, using a dry powder printing technique means that parts can be manufactured on demand, reducing the need for storage of large volumes of fully formed products or mixes, thus increasing the safety over lifetime of a product. The performance of pyrotechnics materials is dependent on a number of properties, including chemical composition, thermodynamic properties and physical form. In combination with composition, architecture could be utilised to understand and control these properties. A bespoke printer capable of additively manufacturing pyrotechnic materials has been constructed with the aim to explore this research area. In this presentation, we compare the burn rates of AM thermites and compare them to conventionally fabricated compositions and discuss the effects of the print parameters and confinement. We conclude with the results from the burning of AM thermite structures and compare their performance with conventionally prepared equivalent thermite examples.
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    Printing powerful powders: evaluating static and dynamic behaviour
    (Cranfield University Defence and Security, 2024-11-13) Zyga, Jowita; McGee, Christine; Humphreys, Lisa; Stennett, Christopher
    Additive Manufacturing (AM), commonly referred to as 3D printing, is a promising manufacturing technique, enabling near full control of the final product’s properties. With its unique approach to complex objects manufacturing, AM is investigated for its suitability of manufacturing with a wider range of materials. Despite the global research on AM of Energetic Materials that has already been conducted, final energetic devices often offer poorer product performance, compared to traditional manufacturing techniques. Reasoning for poorer outcomes could be attributed to the need for adapting and modifying Energetic Materials for AM purposes. To make the materials suitable for AM, there is a need for material modification, such as mixing energetic ingredient with solvent or binder, both of which often result in reducing the desirable outcome: the use of solvent can lead to uneven drying and shrinkage (and therefore producing voids within the product); too much binder is often responsible for low energetic density, therefore causing high burn rates and detonation velocities to be inaccessible. To overcome that, it would be beneficial to use raw, unmodified Energetic Materials – in their powdered form. Research conducted at Cranfield University, using Dry Powder Additive Manufacturing has proven, that energetic devices can be successfully printed using energetic powders. However, working with powders is often challenging: a lack of continuous flow, powder caking or powder-dispensing nozzle blockages are often experienced. To maximise the final product performance and avoid above issues, it is necessary to understand powder behaviour: its dynamic flow, bulk, shear and process properties. A deep understanding of those properties and their effect on manufacturing process is a crucial step to further developing this AM technique. Current methods of powder characterisation are typically limited to determination of 3 parameters: Angle of Repose, Carr (Compressibility) Index and Hausner Ratio. Scientific community have, however, proven these methods to be unreliable, proposing more thorough ways of powder studies: powder rheometers. Despite their growing popularity, analysis and interpretation of test results can still pose some challenges. Current research focuses on gaining better understanding of powder rheology and recognising how investigated powders’ properties translate to their behaviour during the printing process.
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    Towards understanding the detonation properties of additively manufactured RDX: Dry powder printed
    (Royal Society of Chemistry, 2022-06-22) McGee, Christine; Stennett, Christopher; Clements, Jim; Vrcelj, Ranko
    Research into additive manufacturing (AM) has been steadily expanding over the past five decades. Where once only polymeric materials could be reliably printed, AM has been adapted to print with a range of materials such as biological, metallic, ceramic and even foodstuffs. The advantages of manufacturing in an additive manner include; a) a layer-by-layer approach allows the creation of architecturally complex structures, b) a reduction in weight, c) lessening of waste and d) the ability to create parts that that are otherwise difficult or too costly to produce. 1,3,5-Trinitro-1,3,5-triazinane (RDX) is regularly used in explosive systems. Its detonation properties when conventionally manufactured are widely researched and broadly understood. However, recent advances in additive manufacturing technologies have led to greater interest in utilising RDX in this manner. There is growing evidence that emerging formulations and printing methods are changing the detonation properties of RDX composites, the critical diameter among them.1 This study reports on beginning to understand the detonation properties of additively manufactured RDX via a dry powder printing method.