Over many years there has been sustained pressure for the development of structural components that will enable reduced energy consumption and emissions from all forms of vehicle for transportation without prejudice to performance. Such reduction essentially requires weight reduction. To do this whilst maintaining mechanical strength and rigidity performance requires increased yield and fatigue strength to weight ratios and Young’s modulus to weight ratios. This leads to hybrid material structures, typically polymer composites with high strength and modulus fillers. Additional mechanical improvements such as impact corrosion; fire and lightning strike resistance lead to sandwich like structures with alternating metal and filled polymer layers. Civil air transport is the prime example of where such materials are in the ascendency with the recently launched Boeing 787 (Dreamliner) containing 50% by weight of composite -mostly carbon fibre reinforced polymer (CFRP) compared with 12% in the 777 launched in 1990. The Airbus 380 with the highest of all passenger capacity (up to 656) contains 40% by weight of composite mostly CFRP but also including a pioneering use of glass fibre aluminium reinforced epoxy laminate material (GLARE) for upper fuselage panels. One obvious advantage of GLARE is that is lighter than Aluminium (Al) whilst retaining all the advantages of Al i.e. impact, corrosion and fire resistance.
It is too early for the long-term performance of such innovative composites to be known, in service
inspection for defects is difficult because of the complexity, but the risks are substantial. Defects are
likely to occur throughout the entire volume of composite structures rather than localised at riveted,
bolted or welded joints which is the case with ‘traditional’ all metal/alloy as follows:
- Failed adhesion defects can arise over the entire cross section of sandwich structures and over the entire filler- matrix boundary areas.
- Porosity can occur throughout the entire matrix volume.
- Uneven filler distribution.
- Uneven grain refinement in metals.
All of these defects can lead to effective yield and fatigue strengths far below design intentions and thus initiate structural failure. So there are the needs for:
- Improved processing to reduce the risks of their occurrence.
- A system of defect detection during processing to correct defects at source before release into service.
- Further step increases over the mechanical performance of existing aerospace grade composite are desirable on the already stated energy and emission reduction grounds and are possible through the use of graphene (G) and carbon nanotube (NT) fillers. However to realise this, the agglomeration behaviour of G and NT must be overcome. The UltraMAT ultrasonic processing system is intended to answer all of these needs.
The project goal is a novel generic technology (UltraMAT) for materials processing of fluid and semi fluid phases that are widespread in manufacturing, for example, in the welding and adhesive joining of components, the manufacture of bulk composite components and in traditional, Powder metallurgy (PM) Hot Isostatic Pressing (HIP) and semi solid casting.
The key purpose of UltraMAT is to enable production of manufactured components with step improvements in specific strength (yield/ fatigue/ impact) and modulus, fatigue life and thus light weighting; driven by economic and environmental needs to reduce energy consumption and emissions in manufacture and transport. The enabling tool is power ultrasound with purpose shaped force fields for controlled movement and size creation of uniform Nano structures to enable:
- Production of homogeneously distributed and shaped Nano scale particulates, fibres or grains.
- Enhancement of interlayer and filler-matrix adhesion bonds.
v1.6 UltraMAT – D7.2 Preliminary Exploitation Plan 5 UltraMAT will be validated through the fabrication and testing of samples of a number of key
structure/joint types of growing importance especially in aerospace or automotive bodies/engines:
- Titanium (Ti) / Al fibre laminates
- Ti/Al metal matrix composites with fibre/ particulate (ceramic TIC/SIC),
- Ti/Al laser welding and
- Al semi solid casting.
Homogenisation performance will be studied using graphene (G) and carbon nanotubes (NT) because the strong agglomeration tendencies of G and NT is impeding their ability to realise commercially, components of ultra-high specific strength. In short pulse echo mode, UltraMAT will self-evaluate its performance on line aided by predictive big analytics.