Micro-XCT Characterization and Numerical Analysis of Bending Damage Mechanism in Carbon Fiber Plain, Twill and Winding Composite Tubes

Zhongxiang Pan,Heng Ma,Zhenyu Wu,Xiaohong Zhou 한국섬유공학회 2020 Fibers and polymers Vol.21 No.4

Transverse bending damage morphologies of carbon fiber composite tubes with different ply structures wereinvestigated by the micro-XCT characterization. Structural effects of the plain, twill and winding on the damage mechanismwere analyzed. The experimental results present fiber-resin cracking, interlayer delamination and fiber tows breakage withstructural deformation from the peak load to final catastrophic failure. Woven fabric plies in the plain and twill compositetubes cannot be effectively slipped because of their tight interlaced structures, which makes the load propagate along the warpand weft fiber tows, resulting in more fiber tows breakage under bending-induced stretching. There is no interlaced effect onthe failure mechanism for the winding tubes, resulting in a fact that the bending load can only be transferred from the fiberresinor the layer-to-layer interface, with more interlaminar slippage and obvious springback behaviors under in-plane shear. For investigating the interlaced effect on failure mechanism, plain and winding models under transverse bending wereestablished using continuous shell elements, and different constitutive description were used to simulate interlayer failure andintra-layer failure behaviors. By comparing the numerical results with the experimental ones, the influence of the fabricstructure on the failure behavior of the tube were analyzed.

Comparison of the higher diffraction order images in methyl-red-doped liquid crystal films

Dewei Gong,Zhongxiang Zhou,Chunfeng Hou,Yongyuan Jiang,Hao Tian 한국물리학회 2009 Current Applied Physics Vol.9 No.4

We investigate the change of higher diffraction order images in holographic image storage and reconstruction process. In experiments, an s-polarized Ar+ laser (488.0 nm) was used to record permanent grating in the dye-doped liquid crystal, 4,4'-n-entylcyanobiphenyl (5CB) doped with 1 wt% methyl-red (MR), at a small incident angle. Higher diffraction order images were observed when the signal beam was focused in front of and behind the film. Then the film was illuminated by an s-polarized He–Ne laser (632.8 nm) in the direction perpendicular to the surface. The higher diffraction order images were reconstructed. A theory about the change of higher diffraction order images is developed, which is in good agreement with experimental results. The results show that the higher diffraction order provides a useful method for optical information processing. We investigate the change of higher diffraction order images in holographic image storage and reconstruction process. In experiments, an s-polarized Ar+ laser (488.0 nm) was used to record permanent grating in the dye-doped liquid crystal, 4,4'-n-entylcyanobiphenyl (5CB) doped with 1 wt% methyl-red (MR), at a small incident angle. Higher diffraction order images were observed when the signal beam was focused in front of and behind the film. Then the film was illuminated by an s-polarized He–Ne laser (632.8 nm) in the direction perpendicular to the surface. The higher diffraction order images were reconstructed. A theory about the change of higher diffraction order images is developed, which is in good agreement with experimental results. The results show that the higher diffraction order provides a useful method for optical information processing.

Feedback control design for intelligent structures with closely-spaced eigenvalues

Zongjie Cao,Zhongxiang Lei 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.5

Large space structures may have resonant low eigenvalues and often these appear with closely-spaced natural frequencies. Owing to the coupling among modes with closely-spaced natural frequencies, each eigenvector corresponding to closely-spaced eigenvalues is ill-conditioned that may cause structural instability. The subspace to an invariant subspace corresponding to closely-spaced eigenvalues iswell-conditioned, so a method is presented to design the feedback control law of intelligent structures with closely-spaced eigenvalues in this paper. The main steps are as follows: firstly, the system with closely-spaced eigenvalues is transformed into that with repeated eigenvalues by the spectral decomposition method; secondly, the computation for the linear combination of eigenvectors corresponding to repeated eigenvalues is obtained; thirdly, the feedback control law is designed on the basis of the system with repeated eigenvalues; fourthly, the system with closely-spaced eigenvalues is regarded as perturbed system on the basis of the system with repeated eigenvalues; finally, the feedback control law is applied to the original system, the first order perturbations of eigenvalues are discussed when the parameter modifications of the system are introduced. Numerical examples are given to demonstrate the application of the present method.

Study of Several Silica Properties Influence on Sapphire CMP

Haibo Wang,Zhongxiang Zhang,Shibin Lu 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

Colloid silica using as abrasive for polishing sapphire has been extensively studied, which mechanism has also been deeply discussed. However, by the requirement of application enlargement and cost reduction, some new problems appear such as silica service life time, particle diameter mixing, etc. In this paper, several influences of colloid silica usage on sapphire CMP are examined. Results show particle diameter and concentration, pH value, service life time, particle diameter mixing heavily influence removal rate. Further analysis discloses there are two main effect aspects which are quantity of hydroxyl group, contact area for abrasive density stacking between abrasive and sapphire. Based on the discussions, a dynamic process of sapphire polishing is proposed.

Three-point Bending Behavior and Energy Absorption Capacity of Composite Tube Reinforced by Gradient Braided Structure in Radial Direction

Zhenyu Wu,Yong Shen,Zhongxiang Pan,Xudong Hu 한국섬유공학회 2019 Fibers and polymers Vol.20 No.7

This study aims to investigate the radial gradient structural effect on energy absorption and failure behavior ofbraided composite tubes. Two-layer tubular braided fabrics were fabricated using over-braiding technology with three typesof radial gradient configurations in terms of uninform, descending and ascending pattern. The structure of surface layertouching with indenter roll was found to have a significant role on the bending behavior and failure mode. The compositetube possessing the small angle surface layer tends to fail in top-surface mode characterized by compression damage incontact area between indenter roll and tube. With the increasing of the braiding angle in surface layer, the bottom-surfacefailure mode characterized by penetrating crack in circumferential direction was observed, which accompanies abruptlyloading drop and loss of energy absorption capacity. In addition, the tube in descending gradient pattern contributes to higherflexural modulus and peak load due to high fiber volume fraction, while keeps top-surface failure mode because of loadspreading ability provided by surface layer with small braiding angle. The results show that a proper selection of stackingsequence and braiding angle in multi-layer braided tube is capable of effectively enhancing the energy absorption of tubalstructures under bending load.

Diffraction behavior of an azo-dye-doped nematic liquid crystal without applied electric field

Hongyue Gao,Kaiyu Gu,Zhongxiang Zhou,Yongyuan Jiang,Dewei Gong 한국물리학회 2008 Current Applied Physics Vol.8 No.1

We investigate the dependence of the two-beam coupling diffraction efficiency on the experimental parameters, and hence achieve the optimum experimental conditions for holographic recording in planar Methyl Red-doped nematic liquid crystal film without external electric field. Under the optimum experimental conditions, the diffraction efficiency of a holographic grating is improved to 21.4%, and holographic image with long-term stability is stored in the film. These results provide an experimental basis for holographic data storage in this liquid crystal film We investigate the dependence of the two-beam coupling diffraction efficiency on the experimental parameters, and hence achieve the optimum experimental conditions for holographic recording in planar Methyl Red-doped nematic liquid crystal film without external electric field. Under the optimum experimental conditions, the diffraction efficiency of a holographic grating is improved to 21.4%, and holographic image with long-term stability is stored in the film. These results provide an experimental basis for holographic data storage in this liquid crystal film

Structure, Microstructure, and Piezoelectric Properties of Ytterbium-Doped Potassium Sodium Niobate Lead-Free Ceramics

Huan Li,Wenlong Yang,Zhongxiang Zhou,Hao Tian 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.5

The structure, microstructure, and piezoelectric properties of conventionally sintered Yb-doped K0.5Na0.5NbO3(KNN) lead-free ceramics were investigated. Doping the KNN ceramics with Yb2O3 was effective in inhibiting the grain growth in the KNN ceramics and in densifying the ceramics. The 1.0 wt. % Yb-doped KNN ceramics showed the maximum density, about 96.8% of the theoretical density. X-ray diffraction analysis showed that a small number of Yb3+ ions could be incorporated into the matrix of the ceramicsto occupythe α- or β-sites in the crystal lattice, thereby significantly affecting the piezoelectric properties of the ceramics. Enhanced piezoelectric properties (i.e., d33= 135 pC/N, kp = 34.5%, and Qm = 80.2) were obtained for the 0.50 wt. %Yb-doped KNN ceramics.

Study of Several Silica Properties Influence on Sapphire CMP

Wang, Haibo,Zhang, Zhongxiang,Lu, Shibin The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

Colloid silica using as abrasive for polishing sapphire has been extensively studied, which mechanism has also been deeply discussed. However, by the requirement of application enlargement and cost reduction, some new problems appear such as silica service life time, particle diameter mixing, etc. In this paper, several influences of colloid silica usage on sapphire CMP are examined. Results show particle diameter and concentration, pH value, service life time, particle diameter mixing heavily influence removal rate. Further analysis discloses there are two main effect aspects which are quantity of hydroxyl group, contact area for abrasive density stacking between abrasive and sapphire. Based on the discussions, a dynamic process of sapphire polishing is proposed.

Simulation Research on Control System of Main Converter Unit

Li Xingyu,Zheng Zhongxiang,Wu Dali 제어로봇시스템학회 2019 제어로봇시스템학회 국제학술대회 논문집 Vol.2019 No.10

The main converter unit needs to provide high-quality AC and DC power for the ship AC/DC hybrid power system. The reliability of its control system is very important. In order to study and optimize the control system of the converter unit, it is very meaningful to model and simulate it. The working characteristics and operation requirements of the converter unit in the ship hybrid power system are introduced. According to the control system structure, the corresponding simulation model is built. The simulation results meet the unit operation requirements and provide technical support for optimizing the converter unit control system.

Feedback control design for intelligent structures with closely-spaced eigenvalues

Cao, Zongjie,Lei, Zhongxiang Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.5

Large space structures may have resonant low eigenvalues and often these appear with closely-spaced natural frequencies. Owing to the coupling among modes with closely-spaced natural frequencies, each eigenvector corresponding to closely-spaced eigenvalues is ill-conditioned that may cause structural instability. The subspace to an invariant subspace corresponding to closely-spaced eigenvalues is well-conditioned, so a method is presented to design the feedback control law of intelligent structures with closely-spaced eigenvalues in this paper. The main steps are as follows: firstly, the system with closely-spaced eigenvalues is transformed into that with repeated eigenvalues by the spectral decomposition method; secondly, the computation for the linear combination of eigenvectors corresponding to repeated eigenvalues is obtained; thirdly, the feedback control law is designed on the basis of the system with repeated eigenvalues; fourthly, the system with closely-spaced eigenvalues is regarded as perturbed system on the basis of the system with repeated eigenvalues; finally, the feedback control law is applied to the original system, the first order perturbations of eigenvalues are discussed when the parameter modifications of the system are introduced. Numerical examples are given to demonstrate the application of the present method.