Composite Crack And Impact Damage Monitoring Method Via The Change Of Impendance Of Carbon Nanotube Filling Interface

Due to their excellent material properties such as high specific strength and large specific modulus,composite materials are widely used in civil engineering,aerospace and other fields.However,during service of the composites,it will inevitably work at the environment of high pressure,high temperature,causticity and other adverse service environment,which cause the failures such as internal interface delamination,small extensive matrix cracks difficult to be observed by the naked eye.As service of the materials,the damage will extend and propagate which result in a large potential safety hazard of composite structures.In case of engineering accident,it will bring huge economic loss and human casualties to the society.Thus,composite health monitoring is getting more and more attention of researchers.Traditional detection methods such as ultrasonic testing and radiographic inspection have characteristic of high detection accuracy,however,heavy mechanical equipment and time-consuming as well.Therefore,a method for real-time monitoring and nondestructive evaluation and in-situ monitoring of composite damage has great engineering significance.This paper designs a composite damage monitoring method based on multi-walled carbon nanotubes(MWCNT)filled interface.In the double cantilever beam(DCB)prefabricated mode I crack extension and the Glass fiber/Epoxy(GF/Epoxy)laminate low-velocity impact two tests,it has achieved the right The monitoring of interlayer damage of composite materials can accurately identify and locate the damaged area.The specific research contents are as follows:First,this article mixed the two dispersion processes of ultrasonic dispersion and anionic surface modification to prepare a suspension of multi-walled carbon nanotubes.Subsequently,the Glass Fiber(GF)was immersed in a multi-walled carbon nanotube turbid liquid.MWCNT is deposited and adsorbed on its surface to prepare a MWCNT-based interface sensor,and then Vacuum Assisted Resin Infusion(VARI)is used to introduce the interface sensor into the composite material to achieve integral molding to form a damage self-assessment composite.Secondly,in order to explore the sensitivity of the damage self-assessment composite material prepared by this method to interlaminar damage.We designs a DCB prefabricated mode I crack tensile test for research.Real-time monitoring of the electrical response signal of the MWCNT-based interface sensor,wich was located in the middle layer of GF/Epoxy.The development process of the crack of the DCB specimen,explore the relationship between the two test data.We also derive it on the theory to find out the relationship between the resistance data of the interface sensor and the fracture length based on MWCNT and clarify the mechanism.Thus we achieve the optimization of the monitoring of the interlayer crack length of the DCB specimen based on the resistance growth rate of the MWCNT interface sensor.Finally,in order to explore whether the damage self-assessment composite prepared by this method can accurately identify and locate the damage area.The GF/Epoxy laminate is implanted into the MWCNT interface sensor monitoring network to form a damage selfassessment composite material,and the low-speed impact test of the GF/Epoxy laminate is designed to start research.By collecting the MWCNT-based interface sensor monitoring network resistance value in the laminate before and after the low-speed impact,combined with the matching algorithm,the damage cloud image of the specimen is obtained.Compared with the flaw detection result of the ultrasonic C-scan.The damage area identified by the two Method basically tends to consistency.Based on the MWCNT interface sensor monitoring network,the minimum error between the impact center point of the falling hammer and the impact center point observed on the surface of the test piece is only 2.2 mm.At the same time,the impact response curve of the damage self-assessment composite material and the impact damage morphology of the specimen are analyzed.We found that the implanted MWCNT-based interface sensor monitoring network can diffuse the impact energy through the interface sensor network,thereby improving the ability of the specimen to absorb the impact energy.