Microwave (MW) curing and conventional thermal curing techniques were utilized to cure carbon fiber epoxy composites for solid rocket motor to investigate the effect of curing method on their mechanical and morphological properties. In this work, tensile and inplane shear strength properties together with morphological properties were compared between MW cured and thermally cured composites, and the mechanism for MW curing was analyzed. The study shows that 83% cure cycle time reduction is achieved through MW curing. Mechanism analysis for MW curing indicates the resin at the surface layer and interior parts of the composites is cured with different forms. Temperature monitoring during MW processing indicates the uneven electric field distribution in the domestic MW oven. Fourier transform infrared spectrum measurements reveal that MWs do not initiate any new chemical reactions during the curing process of the composites. Thermal analysis using differential scanning calorimeter reveals higher glass transition temperature (T g ) of MW cured composites compared with thermally cured counterparts. Moreover, the MW cured composites show 17% lower tensile strength than thermally cured composites, whereas a 3% increase of the inplane shear strength is observed for MW cured composites, which is also confirmed via scanning electron microscope by means of better coating the fibers with resin, increased fiber wetting and less fiber pullout. POLYM. COMPOS., 36:1703COMPOS., 36: -1711COMPOS., 36: , 2015

The effect of hydrostatic pressure (HP) on the corrosion behaviour of X80 steel is investigated to assist the development of deep-sea oil and gas resources. The results show that the corrosion current increases as HP increases whereas the charge transfer resistance follows the opposite trend. The corrosion products are composed of γ-FeOOH, α-Fe 2 O 3 and α-FeOOH at atmospheric pressure, while Fe 3 O 4 is only formed at a high HP. Additionally, the inner layer of the corrosion products contains more Fe 3 O 4 compared with the surface corrosion layer. HP accelerates the corrosion rate of X80 steel due to its effect on the chemical and physical properties of the corrosion products, including the promoted reduction of γ-FeOOH and the formation of wider and deeper cracks on the corrosion product layer.

The effect of welding speed on microstructure, mechanical properties, and corrosion properties of laser-assisted welded joints of a twinning-induced plasticity (TWIP) steel was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) analysis, electrochemical test, and micro-area scanning Kelvin probe test (SKP). The results reveal that the welded joints, with a fully austenitic structure, are obtained by laser welding. In addition, the preferred orientation of grains in fusion zone (FZ) increased with the increase of welding speed. Additionally, the coincidence site lattice (CSL) grain boundaries of FZ decreased with increasing welding speed. However, potentiodynamic polarization and SKP results demonstrated that the welding speed of 1.5 m/min renders superior corrosion resistance. It can also be inferred that the corrosion properties of the welded joints are related to the grain size and frequency of CSL grain boundary in FZ.

No abstract

In this paper, polymer packaged fiber Bragg grating (FBG) sensors are installed inside of the combustor wall to monitor the health of solid rocket motor. The responses of sensor embedded in adhesive specimen composed of propellant, insulation and case when subjected to axial and unaxial tensile stress are investigated. The strain distribution and spectrum of FBG were simulated when the specimen suffered from different normal loadings by finite element method and computer simulation technology. The result is validated by axis and unaxis tensile test. It is shown that the proposed type of sensing system can measure the bond stress (the radial stress) in SRMs.