Researchers find composites self-healing at low heat
September 21, 2016 - United Kingdom
Scientists from the University of Birmingham (UK) and Harbin institute of technology (China) have developed a way of allowing composite materials, commonly used in aircraft and satellites, to self-heal cracks at temperatures below freezing and be manipulated to operate at very low temperatures (-60°C), in the paper published in Royal Society Open Science.
The team stated that the method could be applied to fibre-reinforced materials used in situations where repair or replacement is challenging such as offshore wind turbines, or even ‘impossible’, such as aircraft and satellites during flight.
Self-healing composites are able to restore their properties automatically, when needing repair. In favourable conditions, composites have yielded impressive healing efficiencies. Previous research efforts have resulted in healing efficiencies above 100 per cent, indicating that the function or performance of the healed material can be better than that prior to damage.
Three-dimensional hollow vessels, with the purpose of delivering and releasing the healing agents, and a porous conductive element, to provide internal heating and to defrost where needed, are embedded in the composite.
A healing efficiency of over 100 per cent at temperatures of -60°C was obtained in a glass fibre-reinforced laminate, but the technique could be applied across a majority of self-healing composites. Tests were run using a copper foam sheet or a carbon nanotube sheet as the conductive layer. The latter of the two was able to self-heal more effectively with an average recovery of 107.7 per cent in fracture energy and 96.22 per cent in peak load.
The healed fibre-reinforced composite, or host material, would, therefore, have higher interlaminar properties - that is the bonding quality between layers. The higher those properties, the less likely it is that cracks will occur in the future. (GK)
The team stated that the method could be applied to fibre-reinforced materials used in situations where repair or replacement is challenging such as offshore wind turbines, or even ‘impossible’, such as aircraft and satellites during flight.
Self-healing composites are able to restore their properties automatically, when needing repair. In favourable conditions, composites have yielded impressive healing efficiencies. Previous research efforts have resulted in healing efficiencies above 100 per cent, indicating that the function or performance of the healed material can be better than that prior to damage.
Three-dimensional hollow vessels, with the purpose of delivering and releasing the healing agents, and a porous conductive element, to provide internal heating and to defrost where needed, are embedded in the composite.
A healing efficiency of over 100 per cent at temperatures of -60°C was obtained in a glass fibre-reinforced laminate, but the technique could be applied across a majority of self-healing composites. Tests were run using a copper foam sheet or a carbon nanotube sheet as the conductive layer. The latter of the two was able to self-heal more effectively with an average recovery of 107.7 per cent in fracture energy and 96.22 per cent in peak load.
The healed fibre-reinforced composite, or host material, would, therefore, have higher interlaminar properties - that is the bonding quality between layers. The higher those properties, the less likely it is that cracks will occur in the future. (GK)