The effect of coagulation bath concentration on the structure and properties of as-spun fibers was systematically analyzed by means of X-ray diffraction, electron microprobe analysis, and the measurement of boiling-water shrinkage, porosity, and mechanical properties analysis, etc. It showed that with the increase of the coagulation bath concentration, the degree of spin orientation and the crystallinity both increased, the microstructure became compact and homogeneous, and the cross section of as-spun fibers tended to be circular. As a result, the breaking tenacity of as-spun fibers and resultant precursors both increased. Adopting the optimizing coagulation bath technique parameters: DMSO/H2O system, coagulation bath temperature 60°C, coagulation bath concentration 65%, and the minus stretch ratio –30%, the precursors and carbon fibers with high performance were prepared.

A micromechanical model is developed to simulate the mechanical behaviors of discontinuous reinforced composites. The analysis for a representative unit cell is based on the assumption of a periodic array of aligned reinforcements. The minimum energy principle is used to determine the unknown coefficients of the displacement field of the unit cell. The constitutive behavior of composites is studied to obtain the relationship between the main variables of matrix and reinforcements. It is concluded that the flow strength of composites is strongly influenced by volume fraction, aspect ratio of reinforcement, and the strain hardening exponent of matrix. An analytical constitutive relation of composites is obtained. The predicted results axe in agreement with the existing experimental and numerical results.

In order to study the effect of solvent residuals on structure and properties of polyacrylonitrile fibers, the morphology, crystallinity and thermal properties of the fibers were discussed by Electron Microprobe Analysis, X-Ray Diffraction and DSC Analysis. It showed that the cross-section of the fibers with a lower solvent residual tends to be circular. The higher the solvent residuals are, the lower the crystallinity of the fibers and the bigger the crystal size. With the increase of solvent residual, the initial temperature of the fibers’ exothermic peak is in advance and the terminal temperature lags behind, the peak temperature increases, and the heat release also increases. Excessive solvent residuals make the heatrelease reaction very violent and the heatrelease increases. The ladder-shaped cyclation structure formed during the preoxidation process often breaks down because of the instant vast heatrelease.

The binary eutectic of lauric acid-stearic acid / expanded perlite composite phase change materials (PCM) was prepared using the method of vacuum impregnation. The structures and properties of this composite PCM were characterized by FT-IR, SEM, DSC and TG analysis. The results showed that the binary eutectic of fatty acid had been composed with porous skeleton expanded perlite completely in a physical method, the phase transition temperature of composite PCM was about 33.0 °C and latent heat was 131.3 J/g. it had a good thermal stability after 100 times of recycling and gave the phase transition temperature 33.5 °C and the latent heat of 128.1 J/g respectively.

In order to release the important information on the structural constitution of Japanese precursor, comparative study on structure and properties of Japanese and self-made precursors were carried out by X-ray Diffraction (XRD), infrared spectrometer (FTIR), element content analysis and the breaking tenacity. It was found that Japanese precursor contains cyano group (–CN) and may contain styrene sulfonic acid amine, while not containing the carboxyl and ester carbonyl, that is, not containing MA. The XRD pattern of Japanese precursor around 10° appears a new crystalline diffraction peak, and the crystal size becomes lower. The cross-sectional shapes of Japanese precursor are circle, with uniform and compact structure, thus its mechanical properties is superior.

No abstract

A strain measurement system for fiber optic is established based on digital image processing techniques. The hardware of the system is consists of a light source, optical fiber cable tensile equipment, CCD camera and image acquisition card. Hardware equipment was selected by the technical requirements of the system, such as measurement accuracy, velocity and so on. The software of the system, including image acquisition module, data processing module, edge detection module, image measurement module and image storage module, is designed.

In order to release the relationship between technics variables and properties of PAN fiber, the evolvement of crystalline structure of PAN fiber during the wet spinning process was studied by X-ray diffraction(XRD), the measurement of the solvent residuals, boiling-water shrinkage and breaking tenacity. It is found that the drawing and removal of solvent can improve the tenacity, especially the drawing can improve degree of orientation and crystallinity, and the collapse process can stabilize the orientation and crystalline structure.