Characterization of moisture effect on static and fatigue performance of epoxy resin using thin-film specimen on dynamic mechanical analyzer

A novel method of characterizing moisture effect on mechanical performance of epoxy resin is presented in this paper. A 50-µm-thick layer of cured epoxy resin was fabricated and cut into strips of 4 mm wide and 30 mm long as specimens to be tested on a dynamic mechanical analyzer equipped with thin-film tension clamp. Static tension and force-controlled tension–tension fatigue tests were first carried out using thin-film specimens made from Momentive 135/137 and BASF 5400/5440 epoxy resin systems without applying moisture, and results were compared with those obtained using conventional dog-bone specimens to validate the proposed testing method. Another batch of thin-film specimens were then immersed into deionized water, and the weight gain was recorded regularly until full saturation to obtain the absorption curve. Static and fatigue tests were performed using thin-film specimens made from BASF 5400/5440 with 55% and 100% saturation of moisture respectively, to evaluate moisture-induced material degradation. The aging effect on BASF 5400/5440 caused by cyclic water immersion and drying process was also assessed by performing static and fatigue tests using fully dried thin-film specimens after aging. It was concluded that the combination of thin-film specimen and dynamic mechanical analyzer would yield as good measurements of tensile strength and fatigue life as conventional dog-bone specimen does, and the small thickness of thin-film specimen would greatly reduce the time to reach a certain level of moisture content, facilitating further studies on effect of moisture ingression on polymeric matrix composites using multi-scale approaches.

The Design and Preparation of Composite Gypsum Boards Absorber Based on Phase Modulation Membrane

According to the principle of electromagnetic wave absorption, functionally reforming thermal insulating materials for building, through designing and theoretically simulating of the λ/4 model, the article has successfully prepared EPS composite gypsum boards for electromagnetic wave absorption. The result shows that, a maximum absorption of-18.7dB at 3GHz and 85% of bandwidth below-10dB was achieved under following conditions: using 380Ω/□ resistive film, specimen thickness of 1.50cm. However, by using phase modulation membrane (PMM),it achieved a maximum absorption of-20dB and 100% of bandwidth below-10dB. This new composite materials can be used for electromagnetic interference protection for WLAN and indoor electromagnetic radiation pollution control.

The Design and Preparation of Foam Concrete Absorber for WLAN Anti-Jamming EMW-Absorber

This paper reports that according to the principle of EMW-absorption, thermal insulating EMW-absorber for building was designed and theoretically simulated of the λ/4 type. The EMW-absorption properties of composites in the band of 2-4 GHz were examined, A maximum absorption of-20 dB at 3 GHz and 80% of bandwidth below-10 dB was achieved under following conditions: using 380Ω/□ resistive film, specimen thickness of 2 cm. Similarly, absorbing materials for 2.45 GHz have successfully designed and prepared,a maximum absorption of-17 dB at 2.45 GHz, and 65% of bandwidth below-10 dB can be reached. New materials can be used for electromagnetic interference protection for WLAN and indoor electromagnetic radiation pollution control.

Design and Development of a Biaxial Tensile Test Device for a Thin Film Specimen

In this article, the design and development of a biaxial tensile test device and its specimen are described. The device, which was designed for evaluating the mechanical characteristics of a thin film specimen under in-plane uniaxial and biaxial tensile stress states, consists of four sets of a piezoelectric actuator, a load cell, a linear variable differential transformer (LVDT), and an actuator case including lever structures with displacement amplification function. The structures fabricated by wire electrical discharge machining are able to amplify the actuator’s displacement by a factor of 3.8 along the tensile direction. The biaxial test specimen prepared using conventional micromachining processes is composed of a cross-shaped film section and chucking parts supported by silicon springs. After square holes in four chuck parts are respectively hooked with four loading poles, the film section is tensioned to the directions where the poles get away from the center of the specimen. Tensile strain rate can be individually controlled for each tensile direction. Raman spectroscopic stress analyses demonstrated that the developed biaxial tensile test device was able to accurately apply not only uniaxial but also biaxial tensile stress to a single-crystal silicon (SCS) film specimen.

Direct Observations of Relaxation of Si/SiGe/Si on Insulator

Microstructural evolution is directly observed when the cross-sectional film specimen of Si/SiGe/Si on insulator (Si/SiGe/SOI) is heated from room temperature (R.T., 291 K) up to 1113 K in high voltage transmission electron microscope (HVEM). The misfit dislocation at the lower interface of the SiGe layer begins to extend downwards even at 913 K. The lower interface takes the lead in roughening against the upper interface of the SiGe layer. The roughened interface is ascribed to elastic relaxation. As misfit strain is partially transferred to SOI top Si layer and misfit dislocation is prolonged at the lower interface, the roughened interface turns smooth again. Thereafter, the misfit dislocations are introduced into the upper roughened interface of the SiGe layer to release the increased misfit strain. It is suggested that the microscopic relaxation of the SiGe layer is related to dislocation behavior and strain transfer.

Re-evaluation of formulae for X-ray stress analysis in polycrystalline specimens with fibre texture: experimental confirmation

Line splitting or line broadening of an X-ray Bragg reflection owing to a three-dimensional or biaxial load on a cubic polycrystalline specimen with 〈111〉 fibre texture has been predicted by Yokoyama & Harada [J. Appl. Cryst.(2009),42, 185–191] if the specimen is in the symmetry of the Laue classm{\overline 3}m. By using a TiN film specimen and a high-precision four-circle diffractometer with a laboratory X-ray source, it is shown that the profile of the 420 reflection is substantially different with and without biaxial load and also depends on the measurement direction, while the profile of the 222 reflection does not change. These results are quantitatively in agreement with the theoretical prediction, although the theory is based on the Reuss model of elasticity.

Fracture Toughness of Titanium - Titanium Nitride Multi-Layer Thin Film

Thin film specimens of titanium - titanium nitride multilayer erosion resistant coating were prepared using liftout technique in Focused Ion Beam - Scanning Electron Microscope (SEM). The fracture toughness of the thin film specimen was measured in situ using a cantilever bending experiment in SEM to be 11.33 MPa/m0.5, twice as much as conventional TiN coatings. Ti–TiN multi-layer coatings are part of a new class of advanced erosion resistant coatings and this paper discusses an experimental technique to measure the fracture toughness of these coatings.

Fabrication of the Bulk Amorphous Ni-W Alloy by an Electroforming Process

A 2mm-thick bulk amorphous Ni-W alloy is formed by applying a new electroforming process and its states are investigated by the XRD analyses and the EDS measurement. The homogeneities of the electroformed alloys are evaluated by the linear analyses on the cross sections of the sample. The fluctuation of the millimeter-scale W-concentration of the bulk amorphous alloy obtained in the present work is reduced to almost the same as that of the bulk nanocrystalline alloy reported in the previous work. Compared to the thin-film specimen produced by the conventional electroplating processes, the gradient of W-concentration of the bulk amorphous specimen can be reduced to two-fifth in the micrometer-scale profiles. Therefore new electroforming process can be successfully applied to the fabrication of the bulk amorphous Ni-W alloy.