Thermal Deformation Field Analysis And Defect Detection Of Epoxy Resin Based On Optical Coherence Tomography

The emergence of high-performance composites makes it gradually replace the original single materials and become an indispensable part of the development of Industrial Science and technology.It is the key to the lightweight of modern advanced equipment structure.However,with the increasing complexity of composite application scenarios,the challenges are also increasing.In order to eliminate the potential safety hazards in practical application as much as possible,the detection technology related to its performance application and defect damage needs to be further improved.Therefore,aiming at the thermal shrinkage characteristics and internal defect detection of epoxy resin composites,the application of phase contrast spectral domain optical coherence tomography in thermal analysis and defect detection of epoxy resin composites is proposed in this thesis.With the advantages of high sensitivity,high resolution,good real-time performance and simple structure,phase-contrast spectral domain optical coherence tomography can realize the imaging of the internal structure of materials,which is a non-destructive tomography technology with micron level detection accuracy.Firstly,this thesis introduces the detection necessity of epoxy resin composites and the detection advantages of optical coherence tomography,and further discusses the development path,research status at home and abroad and related detection technologies of optical coherence tomography.By introducing the imaging principle,demodulation and unwinding mode and out of plane displacement calculation principle of optical coherence tomography,taking epoxy resin as an example,its data processing flow is discussed and summarized,and its performance index and signal component suppression mode are briefly described.Then,according to the principle of system optics,a set of phase contrast spectral domain optical coherence tomography system is designed and built,its optical path structure is described and analyzed from different perspectives,and the functional composition of constant temperature heating system is introduced.Finally,the overall experimental scheme of this thesis is summarized.According to the difference of material cross-section profile and mixture measured by the system,the experiment is divided into two parts:front and rear surface cooling experiment of epoxy resin and content cooling experiment of epoxy resin from two different perspectives of front and rear surface and content.The former combines the phase contrast spectral domain optical coherence tomography system with the constant temperature heating system to measure the surface shrinkage displacement field of epoxy resin experimental samples containing different Si O₂concentrations（0%,0.5%,1%,2%）,obtain the corresponding shrinkage and average temperature displacement curves,and their relations with temperature and Si O₂concentration are further analyzed and discussed;The latter studied and analyzed the effects of defects on the internal deformation and shrinkage displacement of epoxy resin during cooling by setting up complete and defect experimental comparison groups.The experimental results show that the surface shrinkage displacement of epoxy resin experimental samples with different Si O₂concentrations gradually increases with the decrease of temperature,in which the shrinkage first increases rapidly and then slows down,and the average temperature displacement shows a gradual downward trend.By comparing the curve distribution of shrinkage and average temperature displacement,it can be found that both are related to Si O₂concentration,which first increases and then decreases with the increase of Si O₂concentration,which is related to the material characteristics of multicomponent epoxy resin;The deformation trend of complete and defective experimental samples in the cooling process is obviously different from that affected by defects,and the existence of defects will lead to great differences in shrinkage variables between defect area and defect free area.Therefore,the location and size of defects can be observed according to the subtle changes of deformation field.At the same time,the"invisible"defects that are invisible to the naked eye and the section contour can also be identified by the irregular changes of the deformation field.The above experiments verify the feasibility of phase contrast spectral domain optical coherence tomography in the analysis of thermal shrinkage characteristics and defect detection of epoxy resin composites,and show that it has certain application value in related detection fields.