Integrating Self Healing Materials and Structural Health Monitoring
Mentor 1
Nathan Salowitz
Location
Union 280
Start Date
28-4-2017 12:20 PM
Description
When engineered structures fail, the consequences can be fatal. In order to proactively prevent this,the two fields of structural health monitoring and self-healing materials are coming together to facilitate a closed loop system. In this system, the structure will be able to detect damage, repair itself, and report to supervisors. This presentation illustrates the recent progress of the self-healing materials side of the closed loop system and preliminary results of ultrasonic damage detection. By casting a single plane of prestrained shape memory alloy Nickel Titanium (NiTi) wires in a thin brick of aerospace grade thermoset epoxy, the brick can be cracked so that only the wires bridge the gap. This composite can be heated at the wire's activation temperature to make the wires contract. Due to prestraining, the wires pull both halves of the brick to return to a shorter length than the length they were prestrained to. Since the halves cannot pass through one another, the epoxy holds the wire at the length it was cast at. The wires want to contract further than the epoxy will allow, so the epoxy halves' fracture faces are kept together and in a way - healed. To detect the damage, piezoelectric sensors are placed with conductive epoxy on either side of the damage. These piezoelectrics double as actuators and sensors; the actuating piezoelectric is used to send out ultrasonic waves that are propagated through the sample and detected by the receiving piezoelectric sensor. By comparing the signals of the current and previous states, it is expected that the material's status, damaged or undamaged, can be known. If self-healing materials can detect and heal without external maintenance, hard to detect damage or damage occurring while a structure is in service can be slowed or stopped altogether before expensive and catastrophic failure occurs.
Integrating Self Healing Materials and Structural Health Monitoring
Union 280
When engineered structures fail, the consequences can be fatal. In order to proactively prevent this,the two fields of structural health monitoring and self-healing materials are coming together to facilitate a closed loop system. In this system, the structure will be able to detect damage, repair itself, and report to supervisors. This presentation illustrates the recent progress of the self-healing materials side of the closed loop system and preliminary results of ultrasonic damage detection. By casting a single plane of prestrained shape memory alloy Nickel Titanium (NiTi) wires in a thin brick of aerospace grade thermoset epoxy, the brick can be cracked so that only the wires bridge the gap. This composite can be heated at the wire's activation temperature to make the wires contract. Due to prestraining, the wires pull both halves of the brick to return to a shorter length than the length they were prestrained to. Since the halves cannot pass through one another, the epoxy holds the wire at the length it was cast at. The wires want to contract further than the epoxy will allow, so the epoxy halves' fracture faces are kept together and in a way - healed. To detect the damage, piezoelectric sensors are placed with conductive epoxy on either side of the damage. These piezoelectrics double as actuators and sensors; the actuating piezoelectric is used to send out ultrasonic waves that are propagated through the sample and detected by the receiving piezoelectric sensor. By comparing the signals of the current and previous states, it is expected that the material's status, damaged or undamaged, can be known. If self-healing materials can detect and heal without external maintenance, hard to detect damage or damage occurring while a structure is in service can be slowed or stopped altogether before expensive and catastrophic failure occurs.
