Experimental Study On Mechanical Behavior And Deformation Of Composites Based On Synchrotron Radiation X-ray

The macroscopic response and damage deformation mechanism of composite materials are important scientific topics in the fields of solid mechanics,material science,physical science and engineering technology.Synchrotron radiation X-ray technology provides effective measures to study such topics.The damage evolution behavior and damage mechanism of carbon fiber/epoxy composite and B4C/Al composites were studied in our work.The main objectives and findings are as follows:· A mini Quasi-static testing machine,a portable Hopkinson bar and a single-stage tabletop gas gun were designed and built in order to conduct the synchrotron radiation X-ray experiments.And based on the synchrotron radiation X-ray in situ ultrafast real-time imaging and diffraction diagnostic techniques,a good experimental platform was provided for the experimental study of material damage evolution with high temporal and high spatial resolution.· Synchrotron radiation X-ray in situ imaging and diffraction diagnosis technique,X-ray digital image correlation(XDIC)technique and split Hopkinson tension bar were used to conduct in situ dynamic tensile experiments on B4C/Al composites with different particle contents.The experimental results indicated that higher particle content leads to lower ductility and higher yield strength.The mesoscopic strain fields indicated that the strain localizations in 30 wt.% B4C/Al appeared denser and was more likely to grow and coalesce to form macroscopic cracks,leading to brittle fracture.The relationship between particle distances of B4C/Al composites and strain concentration nucleation points,and the reason of changes in yield strength and ductility of materials were explained experimentally.· Along with XDIC and tomography,in situ uniaxial tensile experiments were conducted on a T700 carbon fiber/epoxy composite along various off-axis angles.As off-axis angles increased the elastic modulus and tensile strength decreased.The fracture strain showed a non-monotonic trend.The strain field showed distinct tensile and shear strain localization.Deformation bands were approximately along the fiber direction at high off-axis angles which are different than at lower off-axis angles.The tomography indicates that roughness of fracture surface of carbon fiber plate had potential fall as off-axis angles increased.The present study reveals a fracture mode transition of carbon fiber/epoxy composite from mainly tension(fiber fracture)to in-plane shear(interface debonding).· Using synchrotron radiation X-ray and single-stage tabletop gas gun,three kinds of off-axis angles carbon fiber/epoxy composite penetrated by micro particles was studied.The motion history of the projectile inside the target was obtained.The fiber crushing and interface cracking of the carbon fiber/epoxy composite during the process of penetration was observed.The mechanical response of carbon fiber/epoxy composite under penetration loading was orientation dependent.Numerical simulation was conducted on micro projectile penetrating unidirectional carbon fiber plate at high speed.The simulated results agree well with the experimental observations when the penetration direction is perpendicular to the fiber orientation.However,when the penetration direction is parallel to the fiber orientation,the simulation results are inconsistent with the experimental observation results.It maybe that the “debris” produced in the process of penetration have important influence on its penetration resistance.