Effective EMI shielding behaviour of thin graphene/PMMA nanolaminates in the THz range

The use of graphene in a form of discontinuous flakes in polymer composites limits the full exploitation of the unique properties of graphene, thus requiring high filler loadings for achieving- for example- satisfactory electrical and mechanical properties. Herein centimetre-scale CVD graphene/polymer nanolaminates have been produced by using an iterative ‘lift-off/float-on’ process and have been found to outperform, for the same graphene content, state-of-the-art flake-based graphene polymer composites in terms of mechanical reinforcement and electrical properties. Most importantly these thin laminate materials show a high electromagnetic interference (EMI) shielding effectiveness, reaching 60 dB for a small thickness of 33 μm, and an absolute EMI shielding effectiveness close to 3·105 dB cm2 g−1 which is amongst the highest values for synthetic, non-metallic materials produced to date.

Influence of Thermal Conductivity on Stacking Sequence of Hybrid Composites

Hybrid Composites comprising of two or more reinforcement materials are finding increase in demand in diverse field of applications such as building panels, automotive components and aero parts. There is a need to study the thermal properties to find the suitability of hybrid laminates as insulating materials. In this research article an attempt is made to find the thermal conductivity of laminate materials having varying stacking sequence of its reinforcement fibers. The said laminate is produced using hand layup method. It contain seven layers of reinforcement fibers stacked one over other in three different configurations. First the reinforcements kevlar (K49) and basalt fibers are stacked in alternating layers. Second configuration contain bilayers of kevlar or basalt sandwiching the inner three alternative layers. Third configuration contain tri layer of one of the reinforcement fibers sandwiched between bilayers of another reinforcement fibers. Epoxy resin is used as binding cum matrix element in all the hybrid laminates. The produced hybrid laminates are tested for its thermal conductivity and coefficient of thermal expansion. It is found that increasing the number of layers of basalt fibers increased the thermal conductivity of the hybrid laminate. On the other hand, kevlar fibers contributed in reducing the thermal conductivity of the hybrid laminates. Thermal expansion coefficient depended on the presence of basalt fibers as the outermost layers in the hybrid laminates. The hybrid laminates having kevlar fibers contributed in lowering thermal conductivity and also the coefficient of thermal expansion.

Methods in Making Steel-Copper Sandwich Laminates Materials

This research is aimed at developing a method to make steel-copper sandwich laminate materials. The research focused on the method of developing the sandwich material. In a method I, the steel plate arrangement is heated up to austenite temperature and subsequently, a molten copper is poured into it. In method II, the steel plate arrangement is immersed into a molten copper in a temperature of 1200 °C. The result shows that in the method I, the diffusion on the interface layer of steel-copper sandwich laminate is unemployed because of an occurrence of oxidation on the steel surface. On the contrary, in method II the diffusion on the interface of steel-copper sandwich laminate is indicated by higher shear stress, which is 231.88 N/mm2. However, the immersing method needs to be improved to give better products, since cavities caused by trapped air still exist and are reducing the quality of the laminates.Penelitian ini ditujukan untuk mengembangkan metode pembuatan laminat baja-tembaga. Penelitian difokuskan pada metode pembuatan laminat. Pada metode I, susunan pelat baja dipanaskan hingga suhu austenit dan kemudian tembaga cair dituangkan. Metode II adalah merendam susunan pelat baja ke dalam tembaga cair bersuhu 1200 0C. Hasil penelitian menunjukkan bahwa pada metode I tidak terjadi difusi pada lapisan antarmuka laminat baja-tembaga karena permukaan baja mengalami oksidasi saat dipanaskan. Sebaliknya, metode II menunjukkan terjadi difusi pada antarmuka laminat baja-tembaga dengan tegangan geser tertinggi 231,88 N/mm2. Namun, metode II harus diperbaiki untuk memberikan produk yang lebih baik karena masih terdapat rongga akibat udara yang terjebak dan mengurangi kualitas laminat.

Design, Modeling, and Optimization of a Hopping Robot Platform

Laminate devices have the potential to lower the cost and complexity of robots. Taking advantage of laminate materials’ flexibility, a high-performance jumping platform has been developed with the goal of optimizing jump ground clearance. Four simulations are compared in order to understand which dynamic model elements (leg flexibility, motor dynamics, contact, joint damping, etc.) must be included to accurately model jumping performance. The resulting simulations have been validated with experimental data gathered from a small set of physical leg prototypes spanning design considerations such as gear ratio and leg length, and one in particular was selected for the fidelity of performance trends against experimental results. This simulation has subsequently been used to predict the performance of new leg designs outside the initial design set. The design predicted to achieve the highest jump ground clearance was then built and tested as a demonstration of the usefulness of this simulation.

THE IMPACT OF GLASS STYLE AND ORIENTATION ON THE RELIABILITY OF SMT COMPONENTS

Printed circuit board (PCB) glass style and orientation can have a significant influence on thermal cycling reliability of surface mounted components. DfR has conducted thermal cycling (−40°C to 125°C) tests on two PCB glass styles (1080 and 7628). The in plane and out of plane Coefficients of Thermal Expansion (CTE) were measured and found to be about 3–4ppm/°C different in the X-Y directions of the boards. To facilitate the reliability assessment of SMT component reliability four 0-ohm resistor sizes (2512, 1206, 0602 and 0402) were mounted on each board. Each board had 20 resistors with multiple orientations. The overall sample size consisted of 32 resistors of each size per glass style. In addition, the PCBs have two pad sizes. The purpose of these experiments was to develop a model for validating fatigue life predictions for different laminate materials. This paper will present the experimental structure, results of the stress tests and variables on the reliability of the chip components and insight into the development of appropriate models.