LAPI "smart" coating
Project idea is to develop a novel composite material that is covered with a layer of microencapsulated polymer spheres intergated coating (Figure 1). These spheres will provide direct visual inspection as after impact the surface of the composite by changing the colour depending on the severity of the impact. This composite material possesses also self-repairing feature for due to impact these shells containing different resins will broke and disengaged substance will rapidly repair damages of composite material.
Figure 1. Structure of LAPI
"Smart" coatings. Swapan Kumas Chosh. Functional
coatings by polymer microencapsulation. 2007.
Epoxy resins are often used as a matrix in order to achieve high structural strength and stiffness of the lightweight structure. However, epoxy based composites are brittle and unable to plastically deform. This results in energy absorption via the creation of defects and damage. The damage often manifests itself internally within the material as matrix cracks and delaminating, and can thus be difficult to detect visually.
Detection of structural faults in wide areas of composite usage is of utmost importance to ensure safety and security of people and equipment. Undetected faults in the structure of marine vessels or aircrafts may result in catastrophic consequences regarding passenger safety.
There are numerous successful composite non-destructive testing (NDT) techniques available:
· X-ray Microscopy
· Radiography
· Energy Dispersive Spectrometry (EDS)
· Scanning Acoustic Microscopy (SAM)
· Infrared Thermography
· Laser Shearography
The problem with these techniques is that they often require removal or detachment of the component from the structure in order to be evaluated.
Alternative approach to NDT technique for fasten structural components may be watched in nature. Living organisms provide inspiration for innovations in many different fields. Biomimetics is the field of the engineering science in which inspiration is obtained from biological systems for the design of novel fabricated materials and structures. Natural systems have the capacity to sense their environment, process this data, and respond. However, the mechanisms behind the biological structures are tremendously complex.
LAPI project Consortium has developed a “smart” coatings concept that is based on coating’s colour response when substrate is subjected external force, compression, impact or another stress up to damage or rapture. Its realization has become a novel, low cost visual based inspection technique for advanced composite materials and structures.
Figure 2. Colour response of a “smart” coating in respond to a applied external force F.
Colour response appears as a visible colour (Figure 2) change because of a pH change as stimuli. This concept involves microencapsulated leuco dyes and colour developers embedded into the coating formulation. The dyes are released from capsules and mixed with the developers when the coating experience mechanical stress.
Figure 3. Colour intensity and a size of the “bruise” indicate when the substrate is damaged and no longer offers its peak mechanical performance.
A perspective application of this concept is using in polymer composite materials’ products and structures, e.g., industrial, sport, and police helmets. The coating will indicate with colour intensity and a size of the “bruise” (Figure 3) when the helmet’s substrate material has experienced an impact of sufficient force to deform permanently a portion of the substrate material and when the helmet no longer offers its peak level of performance, and should be replaced to save potentially lives.
Perspective applications of this concept include using these “smart” coatings also on boat hulls, wind turbine blades and composite load-carrying components used in civil engineering.
Contact:
Kalev Piirimägi
CEO
LAPI MT AS
Parksepa
65509 Võrumaa
Estonia
