Lightweight composite material could be a 'game changer'

An anonymous industrial estate on the outskirts of Basingstoke might not seem the place for the start of a revolution in lightweighting, but if the partnership between Composite Metal Technology (CMT) and C&J Antich & Sons lives up to expectations, then perhaps the town best known for its plethora of roundabouts will have another, more impressive, claim to fame.

More than a decade in development, Fibacore is an advanced metal matrix composite (MMC) that is the combination of 3D weaving technology and advanced fast cycle casting, which brings a step change improvement in MMC component cost.

Fibre inserts are placed in strategic positions on components to tailor strength and stiffness, while removing weight. What makes the material particularly interesting is its ability to tolerate shock loads, making it suitable for suspension and engine components, areas that have traditionally been difficult to lightweight cost effectively.

The material offers properties that exceed most other materials currently used for automotive structures. Compared to aluminium, Fibacore has four times the longitudinal stiffness at 240GPa, three times the longitudinal tensile strength at 1600MPa, and five times the longitudinal compressive strength at 1700MPa. This is combined with 30% lower thermal expansion and minimal elongation. Admittedly, it is 26% denser than aluminium, but it is still half that of cast iron, with greater stiffness and strength.

And, a problem with existing 'lightweight metals' is that they are not 'package efficient'. Aluminium components, for example, tend to be bulkier than they would be in steel. And carbon fibre, at least for some parts like suspension and inside the engine, is either prohibitively expensive or unfeasible.

"What this means is that in addition to significant weight saving, components manufactured from, or strengthened with, Fibacore can be dramatically smaller for improved packaging," says David Price, CMT's commercial director.

Antich and CMT are currently working with Jaguar Land Rover in a project funded by the Technology Strategy Board, to develop components with this type of structure.
It has produced a mock-up for the Jaguar F-Type's suspension upright to show how the material can be incorporated, in principle, to increase component stiffness. Using the Al-Fibacore insert, the mass and volume have been reduced 30% by adding less than 0.2kg of inserts. And there's also a 20% improvement in stiffness.

Cost competitive
While Fibacore's cost is currently too high for mass volume production, Price says: "We're getting there. Typically we see a 10-25% increase in cost from using this material, depending on how much is needed and where. We're now hitting the metrics that the higher-end OEMs are applying, in terms of what they will pay for each kilogram saved. And OEMs will pay more for components that are in critical packaging areas such as the engine or suspension system. But, we're feeling quite bullish that we can improve further on cost."

Cast components reinforced with woven inserts of continuous alumina ceramic fibres make Fibacore attractive for applications such as engine block reinforcement, engine mounts, connecting rods and suspension components. Rotating and reciprocating components tend to be particularly well suited to the material as the reduced inertia directly improves dynamic performance.

However, weight saving is not only a prerogative for the automotive sector with the aerospace, rail, defence and renewable energy industries all potentially looking for lighter materials and solutions.

CMT already produce Aluminium Metal Composites (AMCs) for a number of industries using its unique Advanced Liquid Pressure Forming (ALPF) casting process, the product of nearly a decade of development.

Fibacore is the product of CMT's ALPF process combined with C&J Antich & Sons ability to produce woven 3D preforms in T-, U- and I- cross section shapes. The result is a new and more cost effective AMC that is seeking increasing application.

"Using these 3D preforms has been critical," says Price. "We can get down to £60/kg, compared to £88/kg, using 65% unidirectional Al-Fibacore material."

The process locates 'plates' of 3D woven alumina ceramic fibres within a die, and then over-moulds these with aluminium using the ALPF process. CMT has a collaborative project underway with Bühler to develop die casting machines that incorporate ALPF technology and this work is ongoing.

Perhaps the biggest challenge facing the widespread adoption of Fibacore is that each application demands a unique lay-up of fibres and weaves. Subsequently there's work being undertaken to model the materials performance when it's infiltrated.

"Developing CAE tools will enable us to say a particular weave has these mechanical properties when you infiltrate it," says Price.

"Eventually, there will be a library of materials, so it won't have to be done each time a component is designed."

CMT is currently working with a number of European OEMs and expects the first volume production application to begin in 2016-17, although low volume components are likely to appear before then.

Ian Adcock and Justin Cunningham

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