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FUTURE MANUFACTURING 53
repairability. Table 1 quantifies the key advantages of a typical continuous-fibre-reinforced AMCs (CFR-AMCs). As can be seen, AMCs are a good 50 per cent stiffer than carbon fibre (unidirectional carbon-epoxy composite) in the longitudinal direction, and close to three times as strong in the transverse direction. By retaining their properties at high temperatures, unlike carbon fibre, AMCs are also suited to high service temperature components in applications such as engines, electric motors and defence products. For harsh environments AMCs can have superior fatigue strength to steels. And if AMC components do get damaged while in use, they are more impact-tolerant than carbon fibre, meaning that they retain more performance after damage. Developing AMCs for today’s applications Spearheading the development of AMCs is a UK firm, Alvant. Established as CMT originally in 2003, Alvant’s goal has been the exploration of the potential of Liquid Pressure Forming (LPF) as a process for manufacturing AMCs. This has resulted in the creation of a more sophisticated process known as Advanced Liquid Pressure Forming (ALPF). ALPF is the method by which Alvant brings together aluminium, which acts as the matrix, and the high-strength reinforcement materials to create four AMC materials families, namely AlXal (pronounced AlZal)- a continuous fibre reinforced AMC, ParXal – a particle loaded AMC; AerXal – an aluminium syntactic foam and CorXal; a unique high-performance multi-phase AMC similar in concept to a sandwich material but made in a single-shot process providing ultra-high stiffness and low density (~1.5g/cc). To manage cost and complexity, components are not necessarily manufactured entirely from aluminium matrix composite; for example, if they have regions of low stress where enhanced mechanical properties are not required. In such cases, components can be reinforced locally in a method known as hybrid-AMC. In these applications, performance is provided precisely where it’s needed by using AMC inserts applied to the larger aluminium component. This limits the fibre content, simplifies the AMC insert geometry and reduces costs whilst increasing the performance and capability of the component Alvant now owns the proprietary rights to the ALPF AMC manufacturing process and has already attracted interest in several key projects in aerospace, defence and automotive fields. For many of the Aluminium International Today
Future manu Alvant - Copy.indd 2
Fig 1. A comparison of AMC properties versus four relevant metals and composite materials)
projects they mark the transition from R&D to commercial viability, something that is being reflected through a steep rise in demand for its unique AMC products over the past several years, both nationally and internationally. An alternative to conventional metals and more expensive composites in a host of applications The potential benefits of the materials that Alvant is developing means they have potential uses in a wide range of engineering applications including electrified transport, renewable energy and healthcare but are equally suitable for high-end consumer products that need to be light, strong and capable of sustaining damage such as mobile devices, biomechanical prosthetics, sports equipment and personal mobility products including wheelchairs, and folding bicycles. According to Alvant, where safety and reliability are essential, AMCs could find use applications in high-pressure seals, aircraft landing gear and seats. Where performance, efficiency and precision are vital, use cases include robotics, electric motors and automotive suspensions. And it is their lightweight high strength and stiffness characteristics that provide the automation industry with a method for increased productivity through increased speed and reduced maintenance. The list of possibilities doesn’t stop there AMCs’ capability of withstanding extreme temperatures makes them suitable for components in high-voltage battery systems, unmanned aerial vehicles that fly at high altitudes and vehicle powertrains.
A new sandwich on the menu Looking ahead and taking AMCs one step further, Alvant is working on a customisable metal matrix composite (MMC) multi-phase material called CorXal, that offers a viable alternative to titanium and carbon sandwich composite offerings. (Fig 2) Traditional sandwich materials are typically assembled from carbon composite or unreinforced metallic panes with a variety of honeycomb cores. The metallic pane sandwiches are typically flat, 2D panels, while carbon composite varieties can take 3D forms. Positioned as a sustainable and capable alternative, Alvant’s MMC is produced with a ‘oneshot’ manufacturing process and can significantly increase a component’s strength and stiffness to weight ratios. According to Alvant, the multi-phase material method ensures the product is more resistant to shrinkage, damage and high temperatures, making it eminently suitable for harsher environments. It is also possible to create more complex shapes whilst reducing the post-processing and assembly times usually associated with sandwich panel construction by as much as 30 per cent. Alvant also claims that different material selections for both the skin and core are possible so that the MMC multiphase material properties can be tailored to suit specific requirements at the lowest weight. It is a combination of these highperformance properties when incorporated into a ‘sandwich’ type May/June 2020
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