Characterization of Fiber-Matrix Interface Degradation in a Metal Matrix Compositte

The fracture and failure of fiber-reinforced composites are known to be strongly influenced by the properties of the fiber-matrix interface zone. Since these properties may be altered during processing, or may suffer degradation during service, the quality control of interface zones through nondestructive evaluation techniques is highly desirable. The overall properties of fiber-reinforced composites are related to their microstructure. In particular, the velocity of the average waves that can be transmitted in these materials depends on the elastic moduli and the densities of the constituents as well as the properties of the fiber-matrix interface. Thus, the interface conditions can, in principle, be determined from the measurement and analysis of wavespeeds in these materials. However, in practice, this is not a straightforward exercise due to the fact that the relationship between the overall and microstructural properties of a composite are in general nonlinear and thus may lead to an amplification of measurement errors. It is nevertheless extremely important to develop the capability to monitor the integrity of the fiber-matrix interface, especially in high temperature applications where the composites must operate in harsh environments

Phase velocity and attenuation of SH waves in a fiber-reinforced composite

We consider SH wave propagation in a fiber-reinforced composite which consists of a homogeneous, isotropic matrix, containing long, parallel, randomly distributed circular fibers of identical properties. The scattering of waves in the elastically inhomogeneous medium results in a frequency dependent velocity and attenuation of the coherent wave.</p

Characterization of Fiber-Matrix Interface Degradation in a Metal Matrix Compositte

The fracture and failure of fiber-reinforced composites are known to be strongly influenced by the properties of the fiber-matrix interface zone. Since these properties may be altered during processing, or may suffer degradation during service, the quality control of interface zones through nondestructive evaluation techniques is highly desirable. The overall properties of fiber-reinforced composites are related to their microstructure. In particular, the velocity of the average waves that can be transmitted in these materials depends on the elastic moduli and the densities of the constituents as well as the properties of the fiber-matrix interface. Thus, the interface conditions can, in principle, be determined from the measurement and analysis of wavespeeds in these materials. However, in practice, this is not a straightforward exercise due to the fact that the relationship between the overall and microstructural properties of a composite are in general nonlinear and thus may lead to an amplification of measurement errors. It is nevertheless extremely important to develop the capability to monitor the integrity of the fiber-matrix interface, especially in high temperature applications where the composites must operate in harsh environments.</p

Facile and mass-producible Ni-added iron nanowires with excellent microwave absorbing performance

The application of magnetic nanocrystalline powders as radar absorption materials is increasingly attracting R&D interest. Severe agglomeration and mass production, however, are critical issues for practical application of magnetic nanoparticles. In the present study, iron nanowires with varying amounts of nickel addition (0, 1, 10, 30, and 50 wt%) were synthesized via direct reduction of iron salts with the aid of strong NdFeB magnets. The yield rate of these Ni-added iron nanowires (NiFe NWs) exceeded 1 g/min, making them suitable and was feasible for mass production. The characteristics of the so-obtained NiFe NWs were confirmed using field emission scanning electron microscopy, X-ray diffraction, and high-resolution transmission electron microscopy. Composite resins with NiFe NWs additions (3, 5, and 10 wt%) were prepared and examined using the coaxial line method to reveal their microwave absorption characteristics. Experimental results showed that composite resins with 10 wt% NiFe NWs additions possessed superior microwave absorbing properties, with the Ni1Fe99 NWs-added product exhibiting the best performance. When produced with a thickness of 1.7 mm, the reflection loss of the composites reached −39.28 dB at 12.53 GHz. Additionally, the efficient maximum absorption bandwidth was 3.33 GHz, ranging from 14.27 to 17.60 GHz

Effects of Metallothionein-1 Genetic Polymorphism and Cigarette Smoking on the Development of Hepatocellular Carcinoma

ABSTRACT Background. A low expression of metallothionein (MT) has been observed in liver cancer. Such a phenomenon might be influenced by oxidative stress, thus resulting in the cells being more susceptible to DNA damage and apoptotic death. In particular, oxidative stress induced by cigarette smoking might affect MT-1 expression. We designed a hospital-based case-control study to evaluate the effects of MT-1 genotypes and smoking on hepatocellular carcinoma (HCC) occurrence. Methods. A total of 102 HCC patients and 191 matched healthy control subjects were recruited, and epidemiological information was collected. Six genotypes of MT-1 were determined with TaqMan single-nucleotide polymorphism genotyping assays. Results. Individuals possessing MT-1 rs8052394 A, rs964372 G, and rs8052334 T alleles as well as engaging in cigarette smoking had increased risks of HCC; these alleles also had higher linkage disequilibrium. Carriers with MT-1 rs8052394, rs964372, and rs8052334 A-G-T haplotype had a 2.25-fold (95 % confidence interval [CI] 1.46-3.26) risk for HCC development than the control group (A-C-T, the most common haplotype). Compared to nonsmokers with other haplotypes (A-C-T, G-G-C, A-G-C, G-G-T, G-C-T, and G-C-C), nonsmokers with A-G-T haplotype had a 1.93-fold (95 % CI 1.01-3.71) increased risk, and smokers with other haplotypes had a 3.66-fold (95 % CI 1.78-7.54) increased risk, whereas smokers carrying the A-G-T haplotype had the highest risk (matched relative risk 6.72; 95 % CI 2.86-15.79) of developing HCC. Conclusions. The MT-1 A-G-T haplotypes are associated with increased risk of HCC, especially in those who smoke. Hepatocellular carcinoma (HCC) is one of the globally common cancers and is the leading cause of cancer death for men and the second leading cause of death for women in 3 Both environmental and genetic factors may also increase the severity of hepatic inflammation. 4-7 A prospective study in Taiwan found alcohol drinking, cigarette smoking, and betel quid chewing were associated with HCC occurrence; the attributable risk for substance-use habits was 25 %. 5 Cigarette smoke contains a large number of chemical substances. It has been proposed that cigarette smoking could induce oxidative stress and decrease antioxidant defences, thus leading to increased hepatocellular damage

Lightweight and Flexible Reduced Graphene Oxide/Water-Borne Polyurethane Composites with High Electrical Conductivity and Excellent Electromagnetic Interference Shielding Performance

In this study, we developed a simple and powerful method to fabricate flexible and lightweight graphene-based composites that provide high electromagnetic interference (EMI) shielding performance. Electrospun waterborne polyurethane (WPU) that featured sulfonate functional groups was used as the polymer matrix, which was light and flexible. First, graphene oxide (GO)/WPU composites were prepared through layer-by-layer (L-b-L) assembly of two oppositely charged suspensions of GO, the cationic surfactant (didodecyldimethylammonium bromide, DDAB)-adsorbed GO and intrinsic negatively charged GO, depositing on the negatively charged WPU fibers. After the L-b-L assembly cycles, the GO bilayers wrapped the WPU fiber matrix completely and revealed fine connections guided by the electrospun WPU fibers. Then, we used hydroiodic acid (HI) to obtain highly reduced GO (r-GO)/WPU composites, which exhibited substantially enhanced electrical conductivity (approximately 16.8 S/m) and, moreover, showed a high EMI-shielding effectiveness (approximately 34 dB) over the frequency range from 8.2 to 12.4 GHz