Alexcom - Chassis design and manufacturing
IFR Automotive’s aluminium extrusion composite system - known as Alexcom® - is a new and highly innovative construction method for the main body structure of a vehicle offering up to ten times the stiffness of a conventional aluminium space frame.
Alexcom can be applied to a wide range of passenger, commercial and military vehicles and offers an immensely strong yet lightweight solution for maximising safety benefits and minimising environmental impacts.
Significantly, this new construction method has enormous potential to be industrialised for large scale series production. The beam elements can be easily bonded together and the manufacturing process lends itself to high level of automation. The system is protected by worldwide patents and is undergoing continual development by the company for different vehicle applications.
Many vehicles designed for low volume production use steel or aluminium tubes formed into a simple three-dimensional structural framework, commonly referred to as a ‘space-frame’, which serves both as a skeletal cage for the body panels, and as the structural lower part of the vehicle or chassis to which the suspension is attached. It also provides mounting points for the powertrain.
The space-frame is essentially the starting point for building the entire vehicle, and its strength and stiffness is highly influential on many aspects of vehicle performance.
Alexcom introduces a tubular beam with special cross-sectional features, including an internal diagonal spar with extensions to the profile designed to accommodate additional strengthening panels. These are incorporated into trapezoidal areas of the space-frame for additional reinforcement.
The special profile tube has been extruded in aluminium to aerospace standards by Alcoa, which has been working closely with IFR Automotive, throughout the research and development phase, to help implement the company’s very precise specifications for this critical component.
Normally the material specified by IFR for the panelling would be aluminium honeycomb sheet but other possibilities include carbon and even Kevlar; which can deliver an extremely sophisticated ultra-high-strength solution for military and motorsport applications.
Alexcom’s special extrusion is smaller and less intrusive than conventional round or square tubes, which normally require the largest diameter (or diagonal) possible for maximum strength and stiffness. The design of the extrusion also helps minimise the number of elemental beams required in a space-frame.
The overall result is that Alexcom offers significant weight reduction, which can help minimise a vehicle’s carbon footprint. It also leads to smaller and more compact vehicle design, because it is less intrusive on the interior space required for occupants.
Alexcom offers substantial safety benefits with increased passive safety relating to occupant crash protection. It’s more resistant to impact forces and the enhanced structural integrity improves energy absorption in a crash.
The improved mechanical performance also means much better car control. Active safety, which relates to a vehicle’s ability to avoid the accident in the first instance, is improved because of the very high level of torsional stiffness that can be achieved, which improves road holding and handling.
In addition, the composite honeycomb structure is extremely well damped to minimise noise, vibration and harshness (NHV), which can help improve vehicle refinement.
Essentially, Alexcom transforms the simple aluminium space-frame into a sophisticated honeycomb shell-like structure that is immensely strong and rigid. When applied a normal family saloon the torsional stiffness is conservatively estimated to be 90,000Nm/deg, which is almost three times that of the current best-in-class vehicle using a monocoque construction. And this is simply using Alexcom with aluminium honeycomb panels throughout, let alone with carbon or Kevlar reinforcement.
As applied to the Aspid sportscar demonstrator, Alexcom is easily integrated with a high strength steel roll cage; a choice of material that is a mandatory requirement of the FIA for motor racing.
Alexcom can provide additional layers of protection. As demonstrated in the Aspid, the cabin is flanked with a triple-layer of protection, employing anti-impact foam sheets commonly used in the motorsport industry, sandwiched between the main space-frame structure and an additional outer section constructed using the same method of tubes and honeycomb panels.
The next step in the development and application of the technology is to scale it up to the production requirements of luxury saloons and high performance sportscar manufacturers building 5,000 to 20,000 vehicles a year – with IFR Automotive as the technology partner.
Summary of benefits:
Versus conventional aluminium or steel chassis
Increased stiffness-to-weight and strength-to-weight ratios
Enhanced passive safety with greater energy absorption in vehicle impacts
Enhanced road handling and active safety
Better NHV characteristics
Less intrusive design
Modular manufacturing capability
Choice of material reinforcement panels
Versus carbon chassis
Much faster to manufacture
Less tooling cost
No specific manufacturing skills required
Easier to ensure build quality
Easier to repair
Modularity in terms material application
Increased life expectation