Carbon-fibre-reinforced polymer (CFRP) composites derive their excellent mechanical strength, stiffness and electrical conductivity from carbon fibres. The mechanical deformation and electrical resistance are coupled in these fibres that make them inherently sensors. Thus CFRPs can be considered as a self-monitoring material without any need for additional sensing elements. However, for this to become reality the conductivity map of the entire structure needs to be constructed and the relationships between the conductivity and various use- and damage-related variables need to be established. Experimental results demonstrate that internal damage, such as fibre fracture and delamination, decreases the conductivity of composite laminates. In general, the information about the damage size and position can be obtained by utilising electrical impedance tomography (EIT)..
Research results of the application of hard-rolling treatment to aluminum surface modification are presented. The main objective of the research presented here was to study the change in fatigue properties, particularly fatigue crack behavior of notched aluminum specimens after hard rolling. The results indicated an obvious improvement in fatigue properties of the aluminum specimens after hard rolling, but the extent of enhancement of fatigue strength was nearly the same or even decreased slightly with the increase of the hard-rolling value. Fatigue crack initiation and propagation behavior displayed different characteristics for specimens with different hard-rolling values. The microstructural change and the appearance of compressive residual stress at the notch were employed to explain the effect of hard rolling on the fatigue properties of aluminum. In addition, a saturation condition was observed in the compressive residual stress introduced by hard rolling. This phenomenon was explained in terms of the intrinsic properties of the material studied in this work.
The hydration of C4AF was retarded by the addition of Na2Si2O5 of up to approximately 0.1mass% and the hydration completely stopped when it exceeded 0.1mass%. Metastable phases, such as Ca2Al(OH)7·3H2O and Ca2Al2O5·8H2O, etc., were produced when C4AF was hydrated in Na2Si2O5 solution, whereas hydrogarnet was formed as the main hydration product when C4AF was hydrated in water. The ion concentrations of Ca and Al in the liquid phase decreased, and at the same time the period for hydrogarnet formation in the paste was delayed with an increase in the amount of Na2Si2O5 added to the liquid phase.
The hydration of C4AF having various surface areas was investigated with Na2Si2O5 solution. The hydration behavior of C4AF depended on the amount of silicate ions precipitated on its surface. The amount of precipitated silicate ions, which hindered the hydration of C4AF, was proportional to the surface area of C4AF. The precipitated silicate ions on the surface of C4AF were founded to be a silica-like material by means of X-ray photoelectron spectroscopy (XPS). They formed a layer approximately 3nm thick on the surface of C4AF.
Hydrothermal reaction of fly ash and slaked lime produces a porous briquette which is composed of amorphous calcium silicate, a tobermorite-like compound and hydrogarnet. It is essential for the molar ratio (calcium oxide)/(silicon dioxide) of the briquette to be 0.3 to achieve high performance in the purification of wastewater through improved microorganism-carrying ability. The chemical oxygen demand (CODMn) index in artificial, non-fecal drainage decreases more rapidly with the use of the briquettes than that without the briquettes. The macroscopic configuration of the briquettes is an important factor in the water-purification ability, although the high specific surface area of the briquettes does not affect the performance. By increasing the circulation flow rate of the wastewater, the purification performance is improved considerably.
When the sin2ψ method is applied to the residual stress measurement of a curved surface, a large-sized X-ray irradiation area causes some errors in the residual stress measured. However, it is difficult to set a sufficiently small irradiation area to a curved surface with a small radius of curvature when the diffraction intensity is weak or the sizes of grains are large. In this study, the focus is put on a spherical surface, and the relation between the residual stress measured and the size of the X-ray irradiation area is investigated experimentally and analytically. Tangential residual stresses of steel-balls used in ball-bearings were measured for various sizes of the X-ray irradiation areas. Numerical analyses simulating the X-ray stress measurement were performed under various conditions: materials, characteristic X-rays and values of the stress. It is found that the geometric effect appears in the gradient of the 2θ-sin2ψ, diagram chiefly and that the non-linearity in the 2θ-sin2ψ relation owing to the geometric effect is not so remarkable. As a result, we have shown a threshold of the geometric effect as a reference standard by a ratio of the irradiation size to the diameter of the sphere, and have proposed a practical formula estimating the actual circumferential stress on the spherical surface from the tangential stress measured and the geometric factors: the diameter of the sphere, the size of the X-ray irradiation area, and the thickness of the masking plate.
In this study, the dependency of the variation in the shape parameter m, which was determined in the two-parameter Weibull distribution function fitted to a strength distribution, on the number of samples, n, was investigated by using data in numerically simulated distributions. By random sampling, five groups, i. e. (a) forty sets of n=5, (b) twenty sets of n=10, (c) eight sets of n=25, (d) five sets of n=40, and (e) two sets of n=100, were prepared for the present analysis. It was clarified that the variation of m-value was enlarged with decreasing the number of samples, and its variation range as an absolute value became larger as the shape parameter determined for the original population is increased. Values of the shape parameter, which were obtained for respective numbers of samples, were normalized by the shape parameter for the original population. By such normalization, it was revealed that a relative m-variation with respect to the number of samples was hardly dependent on the shape parameter for the original population. The simulated behavior of m-variation was also found to coincide with that observed in four-point bending test using a pressureless sintered alpha silicon carbide. Finally, it should be noted that the number of samples to be used in a strength test, which is recommended in JIS, is not always enough for a better understanding of the statistical strength characteristics in ceramics.