Advanced Materials Research Vols. 123-125

Abstract: A method for achieving better dimensional control for composites based on deformation compensation in mold design is presented in this paper. The process-induced deformation of a general angled part, i.e. spring-in, was studied statistically to account for the processing-related uncertainties. The part geometry was modified based on the results from the statistical analysis for offsetting the deformation. The modified part geometry was used to design the mold for resin transfer molding and the mold was made by the CNC wire electrical discharge machining (WEDM) process. Five sample parts were fabricated using the mold and the spring-in angles were measured. The results show that the process-induced deformation is significantly reduced through deformation compensation. This method presented in this paper provides an approach to minimizing the overall process-induced deformation of resin transfer molded parts.

Abstract: Sodium alginate and Chitosan are common bio-medical dressing material, and drug delivery due to their excellent biocompatibility, biodegradability and non-toxicant. The purpose of dressing aimed at accelerating wound healing. In this study, sodium alginate/Chitosan composite solution composed of Chitosan particles and well-stirred sodium alginate solution. The PLA/cotton nonwoven was the base fabric. The sodium alginate/Chitosan composite solution was later sprayed upon the fabric, so a sodium alginate/Chitosan/PLA/absorbent cotton composite dressing was prepared. Calcium chloride was applied to strengthen the bonding between the sodium alginate/Chitosan solution and the fabric. Mechanical property and SEM of the sodium alginate/Chitosan/PLA/ absorbent cotton composite dressing’ were evaluated.

Abstract: Two different types of channels are investigated which have I- and Z-shaped cross-sections with a width of 2mm. Using the numerical simulation method, the influence of wall contact angle to the process of bubble generating and growth up is studied, and the relationship between different channel shapes and pressure drop is also investigated. In the calculation process, the effects of gravity, surface tension and wall adhesion are taken into account. It is found that wall contact angle has a great influence to the morphology of bubbles. The smaller the wall contact angle is, the rounder the bubbles are, and the shorter the bubbles take to departure from the wall, otherwise, the bubbles are more difficult to depart. The variation of contact angle also has effect upon the heat transfer coefficient, the greater the wall contact angle is, the larger bubble-covered area is, thus the wall thermal resistance gets higher, and the heat transfer coefficient becomes lower. The role of surface tension in the process of boiling heat transfer is much larger than the gravity in narrow channels. The generation of bubbles dramatically disturbs the boundary layer, and the bubble bottom micro-layer can enhance the heat transfer. The heat transfer coefficient of Z-shaped channels is larger than that of I-shaped channels, while the pressure drop of the former is obviously higher.

Abstract: The PET-ITO substrate has been usually applied to many flexible applications such as selectively conducting films, flexible printed circuit, display panels, interconnections, terminals, etc., where the PET-ITO substrate has a main role to enhance the performance in the components of touch screen panels, solar cell panels and so on. Today’s flexible technology is issued on forming fine pattern, pattern alignment and mass-productivity on PET-ITO substrates, which is strongly related to thermal shrinkage and expansion of the substrate[1~5]. We investigated in this study the thermo-mechanical behavior of PET-ITO substrate using a thermo-mechanical analyzer (TMA) in order to analyze thermal strain with varying temperature.

Abstract: The FePt films with various thicknesses of 5 to 50 nm are deposited on Si(100) substrate without any underlayer by in-situ annealing at substrate temperature (Ts) of 620°C. A strong (001) texture of L10 FePt film is obtained and presents high perpendicular magnetic anisotropy as the film thickness increases to 30 nm. Further increasing the thickness to above 30 nm, the (111) orientation of L10 FePt is enhanced greatly, indicating that the quality of perpendicular magnetic anisotropy degrades when the FePt film is thicker than 30 nm. The single-layered FePt film with thickness of 30 nm by in-situ depositing at 620°C shows good perpendicular magnetic properties (perpendicular coercivity of 14.0 kOe, saturation magnetization of 473 emu/cm3 and perpendicular squareness of 0.96, respectively), which reveal its significant potential as perpendicular magnetic recording media for high-density recording.

Abstract: The LED chips, packages and related materials have been already key issue on electronic applications and substitution of conventional lights. It is easily expected that the development trend of LED products is nearly the same as that of electronic products with higher performance, higher integration, lower energy and lower cost. And then we also prospect that the dissipated heat from LED chip is to be big problem for a reliability of products, as likely that electronic packages contain heat sink or heat spreader for controlling heat dissipation. In fact, the heat from an LED package with 1~3W LED chip shows a nearly 60~150°C, which affects thermal damage related to performance, joint failure, crack, etc. The thermal via was fabricated with 16 segments of via sizes ranged 0.2~1.2mm and via pitches ranged 0.5~3mm using 1~3W LED, respectively. The thermal resistivity was analyzed by the thermal transient tester with the variation of via sizes and pitches, which was also compared with the temperature difference of the top and bottom side of LED package. As a results, we convincingly proved the relationships between the design of thermal via and the heat dissipation of LED module, which were directly applicable to LED industry.

Abstract: A new empirical model for predicting the permeability of fiber mats is presented in this paper. Permeability data were collected from the NIST reinforcement permeability database and categorized according to the material architecture. It is seen from the data that for each category, permeability is proportional to fiber volume fraction. In order to describe the behavior of permeability vs. fiber volume fraction, the location, scale and shape parameters were introduced for each material category. The model was validated against the experimental data and good agreement was found.

Abstract: We present the modelled local structure for undercooled silicon beginning from its liquid state, ~1730K to ~1550K. The modelling procedure was achieved by using reverse Monte Carlo (RMC) modelling technique fitting to x-ray static structure factors. The calculated radial distribution functions satisfied experimental observes either liquid or undercooled region. To make a detailed analysis on the modelled local environment we have focused on the distributions both average numbers of atoms within first coordination shell and bond angles whereas the uniqueness of model is discussible. In order to construct model that is more close to nature, the minimum and maximum bond lengths and the average coordination number constraints could have been used. The predicted results using RMC technique show that there is a possible structural transition and it slightly transforms into covalent-like bounded open network structure from its metallic structure, while decreasing temperature.

Abstract: Patterned substrates are good candidates to enhance the arrangement of nanodomains in block copolymer thin films. Here, I theoretically demonstrate the possibility to self-assemble block copolymers on top of physically or chemically patterned substrates. The presence of substrate pattern not only enhances the alignment of polymers, but also induces novel new morphologies which were not present in the bulk phase diagram.

Abstract: To predict the progressive damages including the large delamination growth in composite laminates, a new interface de-cohesive constitutive law is developed which is compatible with 3D continuum damage mechanics (CDM). To avoid the difficulties of 3D mesh generation and 3D interface modeling between the layers, the interface element is implemented in the Reddy’s full layer-wise plate theory. An angle-ply laminate is analyzed to evaluate the developed CDM+Interface procedure in edge delamination initiation and evolution at final stage of CDM damage progress.