Showing papers by "Kin-tak Lau published in 2009"

Natural fibre-reinforced composites for bioengineering and environmental engineering applications

Abstract: Recently, the mankind has realized that unless environment is protected, he himself will be threatened by the over consumption of natural resource as well as substantial reduction of fresh air produced in the world Conservation of forests and optimal utilization of agricultural and other renewable resources like solar and wind energies, and recently, tidal energy have become important topics worldwide In such concern, the use of renewable resources such as plant and animal based fibre-reinforce polymeric composites, has been becoming an important design criterion for designing and manufacturing components for all industrial products Research on biodegradable polymeric composites, can contribute for green and safe environment to some extent In the biomedical and bioengineered field, the use of natural fibre mixed with biodegradable and bioresorbable polymers can produce joints and bone fixtures to alleviate pain for patients In this paper, a comprehensive review on different kinds of natural fibre composites will be given Their potential in future development of different kinds of engineering and domestic products will also be discussed in detail

Natural fibre-reinforced composites for bioengineering and environmental engineering

Abstract: Recently, mankind has realized that unless the environment is protected, he himself will be threatened by the over consumption of natural resources as well as substantial reduction of fresh air produced in the world Conservation of forests and optimal utilization of agricultural and other renewable resources like solar and wind energies, and recently, tidal energy have become important topics worldwide In such concern, the use of renewable resources such as plant and animal based fibre-reinforce polymeric composites, has been becoming an important design criterion for designing and manufacturing components for all industrial products Research on biodegradable polymeric composites, can contribute to a green and safe environment to some extent In the biomedical and bioengineered field, the use of natural fibre mixed with biodegradable and bioresorbable polymers can produce joints and bone fixtures to alleviate pain for patients In this paper, a comprehensive review on different kinds of natural fibre composites will be given Their potential in future development of different kinds of engineering and domestic products will also be discussed in detail

Mechanical and thermal properties of chicken feather fiber/PLA green composites

Abstract: Chicken feather fiber (CFF)/reinforced poly(lactic acid) (PLA) composites were processed using a twin-screw extruder and an injection molder. The tensile moduli of CFF/PLA composites with different CFF content (2, 5, 8 and 10 wt%) were found to be higher than that of pure PLA, and a maximum value of 4.2 GPa ( 16 % ↑ ) was attained with 5 wt% of CFF without causing any substantial weight increment. The morphology, evaluated by scanning electron microscopy (SEM), indicated that an uniform dispersion of CFF in the PLA matrix existed. The mechanical and thermal properties of pure PLA and CFF/PLA composites were compared using dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and thermogravimetric analysis (TGA). DMA results revealed that the storage modulus of the composites increased with respect to the pure polymer, whereas the mechanical loss factor (tan δ ) decreased. The results of TGA experiments indicated that the addition of CFF enhanced the thermal stability of the composites as compared to pure PLA. The outcome obtained from this study is believed to assist the development of environmentally-friendly composites from biodegradable polymers, especially for converting agricultural waste – chicken feather into useful products.

Imparting Ultra‐Low Friction and Wear Rate to Epoxy by the Incorporation of Microencapsulated Lubricant?

Abstract: The incorporation of microcapsules containing lubricant oil into epoxy composites leads to materials with ultra-low friction and wear performance. During sliding wear tests, the capsules are damaged by the asperities of the counterface, releasing the oil to the contact area. The lubrication effect of the released oil and the entrapment of wear particles in the cavities left by the ruptured capsules leads to a significant reduction of both the frictional coefficient and the specific wear rate. The approach provides the merits of fluid lubrication but excludes the drawbacks of external lubrication. A minute amount of lubricant oil is sufficient to improve the tribological properties significantly.

Study on the Mechanical Properties of Different Silkworm Silk Fibers

Abstract: Mechanical properties of Bombyx mori, twisted B. mori, and Tussah silk fibers were investigated. Their ultimate tensile strength, elongation at break, and Young’s modulus were examined by performing a uniaxial tensile test on a single fiber. Scanning electron microscopy was used to observe the morphology of two different types of silk fiber, and to measure their apparent diameters from which the cross-sectional area of the silk fiber for stress - strain analysis can be determined. Based on experimental results obtained, it was found that Tussah silk fiber has a relatively high extensibility as compared to B. mori silk fiber and other natural fibers. Weibull analysis was also used to quantify tensile strength reproducibility of the silk fiber. Both single and twisted B. mori silk fibers have a better reproducibility of tensile properties than Tussah silk fiber.

Mechanical and thermal properties of nano-al2o3/nylon 6 composites

Abstract: Nano-Al2O3-reinforced monomer casting nylon (NA/MCN) composites were prepared by using in situ polymerization. The average molecular weight of the matrix nylon was measured using gel permeation chromatography. The thermal-mechanical properties of the NA/MCN composites were characterized by thermo-dynamic mechanical analysis, and the results were compared with micro-Al2O3-reinforced nylon (MA/MCN) composites. A tensile property test was conducted to investigate the mechanical properties of neat nylon and composites. Experimental results showed that the average molecular weight of the matrix nylon filled with nano-alumina had little change and was higher than that with micro-alumina. The glass transition temperature (Tg) and storage moduli of NA/MCN composites were higher than that of neat nylon. During the experiment, it was also found that the tensile strength increased up to 52% when 3 wt.% of nano-Al2O3 particles were added. The thermal and tensile properties of NA/MCN composites were better than those ...

Fabrication and properties of clay-supported carbon nanotube/poly (vinyl alcohol) nanocomposites

Abstract: Clay-supported carbon nanotubes (Cs-CNTs) were used as novel nanofillers to improve the thermal and mechanical properties of a polymer. Cs-CNT/poly (vinyl alcohol) (PVA) nanocomposite films were successfully fabricated, and their relative properties were investigated by using differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. Experimental results showed that the thermal stability and dynamic mechanical properties of PVA were remarkably enhanced by incorporating the Cs-CNTs into PVA matrix. The largest T(g) difference of 14 degrees C was obtained between pure PVA and PVA nanocomposite with 7 wt% Cs-CNTs. Moreover, the storage modulus of PVA was significantly improved by 133% at 50 degrees C, when 7 wt% Cs-CNTs was added to PVA matrix. POLYM. COMPOS., 30:702-707, 2009. (C) 2008 Society of Plastics Engineers

Composite panels for reducing noise in air conditioning and ventilation systems

Abstract: The plate silencer [1] that consists of an expansion chamber with two side-branch cavities covered by a light panel can achieve a desirable noise reduction in broadband theoretically. The concept is similar to drum silencer [Choy YS, Huang L. Experimental studies of drum-like silencer. J Acoust Soc Am 2002;112:2026–35]. To attain optimal noise reduction, either the membrane of the silencer should be of minimal weight while retaining very high tensile strength or the panel should be kept at very high bending stiffness that is dependent on its geometry and mechanical properties. To achieve such goal, various kinds of composite system such as carbon fibres or aluminum were mounted on light core foam to build a noise reflection panel. A design of composite panels which can provide a reduction in panel weight as well as enhance the bending stiffness, is introduced in this paper. Predictions of the new model are to be compared with the normal foam plate in the aspects of noise reflection capability and performance of noise abatement apart from the material properties.

Optimization Effect of Micro Hardness by Nanoclay Clusters in Nanoclay/Epoxy Composites:

Abstract: Nanoclay/epoxy composites have been investigated extensively on their mechanical and thermal properties over the last decade. Researches have been mainly focused on the control of manufacturing a fully exfoliated inter-planar structure of nanoclay platelets inside epoxy resin in order to achieve the maximum mechanical strength of the composites. Nevertheless, in reality, sole dominant structures (both exfoliated and intercalated) are hardly produced in the manufacturing process. Nanoclays would be easily agglomerated to form tiny nanoclay clusters, especially in the extrusion and injection molding processes of epoxy-based components. This paper studies the mechanical performance in terms of micro-hardness of nanoclay/epoxy composites with different nanoclay contents. The size of nanoclay clusters in the composites vary with different nanoclay contents observed by the microscopic examination. The results show that the micro-hardness of the composites could be enhanced by adding a small amount of nanoclays. However, there is an optimal limit wherein the maximum hardness of the composites is measured. Continuously increasing the amount of nanoclay could ultimately decrease the hardness of the composites.

Smart composite materials : selected papers from the international conference on multifunctional materials and structures (MFMS 08) (Hong Kong, 28-31 July 2008)

Abstract: Recently, the development of smart materials and structures (SMS), at the levels of micro and nanoscale, has grown rapidly due to the requirement of an increasing safety margin of all infrastructure, biomedical and engineering (automotive, aerospace and marine) elements The name 'smart' means that a structure (or a material) should be able to respond to environmental changes or external impacts to keep it in a safe condition, without substantially changing its original functionalities Embedding sensor and actuator technology is one of the most popular topics of all SMS disciplines, because these sensors and actuators are very small and do not influence the mechanical, thermal and geometrical properties of the host structures Ideally, these sensors and actuators are also connected to the central system (commonly called the 'brain') to analyze the condition and control the necessary reaction of the structures Recent research on SMS has been mainly focused on embedding tiny sensors and actuators into advanced composite materials The main reason is because advanced composites have been widely adopted for building large life-concerned structures, like airplanes (both Airbus A380 and Boeing 787) A large portion of their structures are made by carbon and glass fiber composites Most of the rotor blades of helicopters are also made of advanced composites in order to reduce their weight and keep sufficient strength to maintain their stiffness However, these structures are subject to many uncertain influences, such as excitation by unpredictable incoming wind with a frequency close to the natural frequency of the structures, for example, blade?vortex interaction As a result, abnormal vibration and noise may be induced that is severely harmful to the structures In this special issue, several types of smart materials and devices that are used for ensuring the safety of structures are introduced It includes: piezoelectric sensors and actuators, nanoconductive particles, shape memory alloys and magneto-rheological elastomers for advanced composite applications The editors would like to express their sincere appreciation and thanks to all the authors for their scientific contribution to this special issue on 'Smart Composite Materials' for Smart Materials and Structures We convey our gratitude to all the reviewers for their time and dedication We applaud IOP Publishing for their support and encouragement of this special issue and the staff for their special attention and timely response