AIRBUS Group Innovation and OliKrom Develop Coatings to Increase Composite Safety

For the past 5 years, OliKrom and Airbus Group, under the leadership of Airbus Group Innovation (formerly EADS), have been working together to create the SMART Composites of tomorrow!

– In May 2016, OliKrom’s technological breakthrough in heat-sensitive coatings was recognized with the SURFAIR Awards for innovation

SURFAIR Awards 2016 for innovation “ThermoSensitive Coatings for Health-Monitoring of CFRP” awarded to Sophie SENANI, Research Engineer, AIRBUS GROUP INNOVATIONS (France). 

– Airbus Group Innovation and OliKrom are also partners in the ANR CHOCOCOMP project “Materials and Processes for Performance Products” (MATETPRO) for the development of “Reversible Piezochromic Coatings for Impact Detection on Composite Supports”.

Due to their low weight combined with excellent mechanical properties, composite materials are widely used for structural applications.

However, they are particularly vulnerable to damage caused by impacts, even of low energy, which can occur during the assembly of parts (for example in the Final Assembly Line). Damage generally localized at the point of impact (delamination, internal transverse cracks) can be more extensive and propagate under fatigue loading, which can lead to a significant decrease in their mechanical strength. This damage may be underlying or barely visible, requiring costly and time-consuming non-destructive inspections to verify the integrity of the composite. Therefore, a visual impact detection system would allow ultrasonic inspections to be focused strictly on the necessary areas.

In this context, CHOCOCOMP aims to develop, characterize and evaluate an innovative impact sensitive and reversible coating to detect and quantify damage on composite substrates. For this purpose, the dispersion of piezochromic pigments (i.e. which change color under the effect of pressure), in a polymer/sol-gel hybrid matrix is a promising approach. An impact energy/response calibration of the coating/substrate will be used to correlate the chemical and mechanical properties of the coating according to its application and the associated substrate. The spray application process is in line with the new technological developments by respecting the eco-efficiency trends strongly linked to the reduction of production and cycle costs.

The strategy of this project has 6 axes:

  • Define the energy threshold corresponding to a damage in the composite to be applied on the coating+substrate assembly

  • Design and optimization of piezochrome pigments

  • Development of impact-sensitive and reversible coatings by incorporating piezochrome probes in a polymer/sol-gel hybrid matrix in order to combine piezochrome properties, mechanical resistance and adhesion to the substrate

  • Characterization of piezopigments and coatings at the macro- and microscopic scale

  • Evaluation of the mechanical performance and the sensitivity to shocks (piezopigments and coatings).

  • Study and correlation with the damage caused to the composite. Study of the coating/composite interface

  • Optimization of the piezopigments synthesis process at pilot scale and of the deposition process (sputtering)

To date, this global scientific approach (chemistry+mechanics+process) has not yet been studied for revealing coatings.

The scientific and technological objectives of this project are ambitious. CHOCOCOMP is the first phase of the complete development of the shock sensitive coating. It is focused on the calibration and development of a material for final assembly applications. The results obtained will serve as a basis for the 2nd phase dedicated to large-scale industrialization. Moreover, the results can then be extended, not only to the requirements in service of aeronautical applications (launchers, helicopters, airplanes…), but can also be extrapolated to many other sectors (automotive, wind energy, nautical…), on various materials (public works, motorcycles, sports…).