(Also see Reflexive, Self-Healing Composites in our portfolio.)
Reflexive composites, self-healing shape memory polymer (SMP) composites for aerostructures integrated into a structural health monitoring system, allow air vehicles to repair structural damage caused by events while in flight such as bird strikes and debris. Such an integrated system would extend the service life of the vehicle and allow it to land safely during an emergency, protecting both the vehicle and its passengers or payload.
Reflexive composites are a bio-inspired technology, mimicking a biological ability to identify and mitigate damage for increased survivability. This is accomplished through the integration of three emerging technologies: healable SMP composites, structural health monitoring (SHM), and intelligent controls.
Reflexive composite systems feature a healable SMP matrix. After sustaining damage and undergoing a subsequent healing cycle, this matrix has been shown to restore up to 90% of original mechanical performance in composite test specimens. This is done by heating the SMP composite above its activation temperature, which causes it to become soft and pliable and to revert to its original shape.
The integrated SHM system autonomously collects data from an outlying grid of piezoelectric sensors, which generates a current when subjected to mechanical stress. The intelligent control system then analyzes the data output from the SHM system to determine any anomalies or damage and determines what actions should be taken. The intelligent control system initiates a targeted healing cycle consisting of discrete heat application to the damaged area through integrated heating elements. The healing process returns the damaged region to a near-net manufactured state through shape memory effect and matrix healing, resulting in significant restoration of mechanical performance and surface quality.
The video below shows two scenes. The first scene is an artistic conceptualization of the operation of a reflexive composite system. A section of a commercial airliner wing becomes damaged due to a bird strike. The SHM system relays data to the intelligent control system, and the control system renders a picture of the damaged area as feedback to the cockpit. Without any need of pilot input, the repair system activates heating elements beneath the damaged area. The reflexive composite "skin" then returns to its original shape and restores mechanical performance through matrix healing. The second scene shows a laboratory demonstration of a prototype reflexive composite panel. A thermochromic sheet shows the temperature change as heating elements are activated around the damaged area, and a time-lapsed sequence shows the composite returning to its original shape.