Health Monitoring Of The Dynamic Stress/strain Of Concrete Structures Under Impact By Flexible Piezoelectric PZT Sensors

The concrete engineering materials would subject to different types of impact load during its long-time service period.Some damages would generate under the impulse load and decrease the safety and service life of the concrete structures.So the real-time monitoring and estimating of the damaging level of the concrete and take necessary actions is of great importance.In this article,we fabricated the flexible piezoelectric sensors based on Lead Zirconate Titanate(PbZr_0.52Ti_0.48O₃)nanofibers.And the PZT piezoelectric sensors were made into smart aggregates after encapsulation.We realized the real-time health monitoring of the concrete under impact by which we could estimate the damage level of the structures.The research contents are as follows:The fabrication and performance of the PZT piezoelectric sensors.The PZT piezoelectric nanofibers were made by electrospinning method.Mixed with polymer PDMS and conductive phase CNTs,we fabricate PZT/PDMS/CNTs composite piezoelectric sensors.The sensing characteristic of the PZT based piezoelectric sensors have further been investigated.Bending strain sensing property has been measured by the stepper motor.Impact stress sensing property has been measured by homemade dropping ball device.The reliability of the output voltages of PZT sensors has been proved by the reverse electrodes test.The fabrication and performance of the PZT based piezoelectric smart aggregates.The flexible PZT composite sensors were made into piezoelectric smart aggregates after been encapsulated of cement and epoxy resin.The mechanical property of the piezoelectric smart aggregates has been measured and proved to be suitable to be embedded in the concrete material.Two methods were introduced to calibrate the piezoelectric smart aggregates,including homemade drop hammer test and electronic universal testing machine test.Experiments results showed that the piezoelectric smart aggregates have great sensing stability and service life.The reliability of the output voltages of the piezoelectric smart aggregates was proved by the electrodes reverse experiment.Measuring of stress/strain of the concrete structures under dynamic impact and ANSYS numerical simulation.PZT based piezoelectric smart aggregates were embedded in desired locations of the concrete blocks during fabrication process.The sensing properties were measured by impact tests,including free fall hammer impact test and microcomputer control electronic universal testing machine impact test.Embedded PZT piezoelectric smart aggregates were calibrated under rigid and soft impact by free fall hammer,and the inner stress and strain distribution was given out by ANSYS simulation.The sensing performance of the piezoelectric smart aggregates embedded in concrete blocks under local stress concentration was studied combined with ANSYS numerical simulation.The sensing abilities of the smart aggregates were also calibrated by the electronic universal testing machine.Inner stress distribution of the concrete blocks under local concentration stress have been measured and proved to be reliable by ANSYS numerical simulation.