In this study, we demonstrate the usefulness of chemical based method in combination with AFM to characterize a wide range of degradable polymer blends. This approach is based on selective degradation of one of the phase in a multi-phase system and the ability of TMAFM to provide nanoscale lateral information about the different phases in the polymer system. Composite films containing different percentage of hydrolyzable polymer were either melt processed/solution casted and then exposed to a hydrolytic acidic environment and analyzed using TMAFM. Pits were observed to form in the blend films. The progressive hydrolysis of the hydrolyzable component in the composite was studied by FTIR analyses. TMAFM phase imaging was used to follow pit growth of the blend as a function of exposure time. The usefulness of the chemical modification/AFM approach in the characterization of renewable porous material membranes is discussed.

Phenolic polymers and phenol formaldehyde resins are of great interest for a number of electronic and industrial applications. Unfortunately, the toxic nature of the starting materials (formaldehyde) and harsh reaction conditions required for the synthesis of these polymers have severely limited their use in today’s markets. We present here an alternative, biocatalytic approach where the enzyme horseradish peroxidase is used to polymerize phenol in the presence of a template such as polyethylene oxide. Here the template serves as a surfactant that can both emulsify the phenol and polyphenol chains during polymerization and maintain water/solvent solubility of the final polyphenol/template complex. The reactants and the reaction conditions of this approach are mild and result in high molecular weight, electrically and optically active, water-soluble complexes of polyphenol and the template used. High molecular weight water-soluble polyphenol/polyethylene oxide complexes were formed. The ionic conductivity and potential use of these polymers as polyelectrolytes for battery and solution cell applications will be discussed.

In this paper a methodology is introduced for the design of structural components made from composite materials for the control of stress. A numerical method is developed for designing functionally graded materials with minimum stress in prescribed sub-domains inside the structure.

Molecular order and morphological order are two characteristics of feather fiber that make it unique. The fiber is highly microcrystalline and is very durable, i.e., resistant to both mechanical and thermal stress. Feather structure at the microscopic level is a complicated mixture of straight and branched fibers held together by a central fiber to form specific macroscopic structures. The proper design of processes to incorporate feathers into composite products 1) preserves the fiber's molecular properties and 2) alters its micro-/macroscopic morphology to conform to existing composite process requirements.

Pb(Zr0.48Ti0.52)O3 (PZT) micro/nano-fibers and mats were synthesized from alkoxides using electrostatic deposition. The PZT micro/nano-fibers precursor, a mixture of zirconium npropoxide, titanium isopropoxide, and lead 2-ethylhexanoate, was deposited under the following conditions: tip-screen distance=15cm, voltage drop between tip and screen of 15kV. The deposited fibers and mats samples were sintered for half an hour at 400, 500, 600, 700, and 800°C, respectively. Sintered mats were characterized using x-ray diffraction (XRD), sintered fibers were characterized using optical microscope, scanning electron microscopes (SEM), Raman microscope, and scanning probe microscope (SPM). SEM revealed that micro/nano-fibers have diameters varying from a fraction of a micron to around 10 micrometer. XRD and Raman spectra indicated that the precursors begin to transform into intermediate phase Pb2Ti2O6 at 400°C, whose transformation into the perovskite phase starts at 600°C and ends at 800°C. Scanning probes microscope (SPM), operated in voltage-modulated dynamic contact mode, revealed the spontaneous polarization domains, with diameters ranging from 0.1 to 0.5 micron, in microfibers, confirming their piezoelectricity.

Novel transition-metal containing hybrid biopolymer-silica aerogels have been synthesized as transparent monolithic structures. The compositions include Ru(III), Rh(III), Co(II), and Pd(II) species, silica and chitosan, and amine-group-containing biopolymer derived from chitin. Due to its aqueous solubility and hydrogen bonding properties, chitosan was homogeneously incorporated into the silica network. These aerogels have densities in the range of 0.25-0.30 g/cm3, BET surface areas in the range of 600-975 m2/g, and refractive indexes below 1.17 (at 632.8 nm). Infrared spectroscopy shows that chitosan is effectively introduced into the silica aerogels, and the transition metal ions can coordinate with the amine sites on chitosan. This combines the metal-ion interaction of chitosan with that of silica aerogels. Transmission electronic microscopy indicates that the particle sizes of silica are about 2 nm. Small angle neutron scattering (SANS) has been used to study the microstructure of these aerogels. A new Small-Particle Mass-Fractal model scattering function, derived from the Teixeira Mass-Fractal model scattering function, was used to fit the SANS data. It was found that chitosan helps to form an open aerogel structure. It supports a structural model in which there are primary particles that connect with each other closely to form clusters, and these clusters serve as a secondary structural unit to form the chitosan-reinforced aerogel network. It also indicates that chitosan reinforces the interparticle connections. The local environments, structures and chemistries of the transition metal ions have been explored. Of special interest in this regard are the magnetic properties of the Ru(III) containing materials, which are consistent with anti-ferromagnetic coupling, and the reactions of the Rh(III), Ru(III), and Pd(II) species with small gaseous molecules.

Monotonic and cyclic fatigue behavior of fibers are of general interest, regardless of the end use of the product whether in a composite or in a fabric. Study of cyclic fatigue behavior of fibers is particularly difficult because of their small diameter (∼10 μm) and high aspect ratio. In this paper, we report some preliminary results of monotonic tension and tension – tension fatigue behavior of a ceramic fiber: Nextel 312 (Al2O3-SiO2-B2O3) fiber. This fiber has a nanocrystalline structure with B2O3 mostly in the form of a glassy phase. The tensile strength data of this fiber showed a Weibull modulus of 4.6, indicating a large degree of variability. Our experiments show clear indication of cyclic loading being more damaging than static loading for Nextel 312. The fracture surface observations of fatigues samples showed some distinctly different features from those observed in fibers subjected to monotonic tension.

A conventional approach to the toughening of brittle materials has been to incorporate fibrous inclusions. These toughen the composite by acting as crack bridges, with energy being dissipated by frictional losses during pull-out of the fibre or by matrix failure on the scale of fibre surface roughness. In all cases, toughening has been achieved only where propagating macrocracks have interacted with an appreciable number of reinforcing inclusions. This paper considers the probability that toughening via crack-bridging in these fibrous and especially particulate toughened materials has not been optimised and proposes the idea that the frequency of interaction between crack and inclusion is strongly increased by un-bonding the inclusion from the matrix. Results from studies on cement-mortars are presented in support of this and show significant improvements in toughness associated with samples in which inclusions are deliberately un-bonded from the matrix in advance of the crack arriving.

Bamboo is a typical composite material which is axially reinforced by very strong fibers. So that, the fibers play an important role for the bamboo structure. The elastic properties of the bamboo culm have been measured only by tensile test so far, which needs a large specimen. Recently ultra-sonic technique, which has a simple procedure and uses a small specimen, has been applied to woods as well as metals. This report reviews about the elastic properties of bamboo and Hemp palm fibers. The Young's modulus and Poisson's ratio of the bamboo fibers are measured by ultra-sonic method with a transmitting wave. On the other hand, the strength of the bamboo and Hemp palm fibers are measured by the tensile tests. Using the volume fraction of fibers in the specimen and mixture principle, the Young's modulus and strength of the fibers and parenchyma were obtained. The fiber has a high strength up to 1GPa and an strong anisotropic property because its axial Young's modulus has 7 times higher than the one in the transverse direction.

The properties and homogeneity of a composite laminate are strongly dependent on structures and microstructures in it. The investigations have shown that the microstructures of carbon fiber-reinforced polymer composite laminates can be visualized by means of acoustic imaging techniques. The frequency of ultrasonic wave to be used is up to 50MHz. The composite laminates to be investigated include unidirectional carbon fiber-reinforced polymer composite laminates, bi-directional carbon fiber-reinforced polymer composite laminates and carbon fiber woven composite laminates. Very useful quantitative information about inside structures of the composites can be visualized in plan-section of the laminates in the depth directions by ultrasonic T-scan imaging technique. Typical results have been represented in this article.

Continuous carbon nanofibers were manufactured using electrospinning technique. The as-spun polyacrylonitrile (PAN) nanofibers were stabilized and carbonized to convert them into carbon nanofibers. The diameters of typical carbon nanofibers were in the range from 100 -500 nanometers. Compared to the vapor grown carbon nanofibers, the electronspun carbon nanofibers were continuous, uniform in diameter, and solid. The electrospun nanofiber samples did not require purification. The carbon nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Electron and X-ray diffraction patterns were obtained and analyzed. Nanocomposites of epoxy resin reinforced with as-spun PAN and carbon nanofibers were fabricated and analyzed. The results showed good potential of continuous carbon nanofibers for nanocomposite and other applications.

Multilayered ceramic composites are very promising materials for different engineering applications. Laminates with strong interfaces can provide high apparent fracture toughness and damage tolerance along with the high strength and reliability. The control over the mechanical behavior of laminates can be obtained through design of residual stresses in separate layers. Here we report a development of tough silicon nitride based layered ceramics with controlled compressive and tensile stresses in separate layers. We design laminates in a way to achieve high compressive residual stresses in thin (100-150 micron) Si3N4 layers and low tensile residual stresses in thick (600-700 micron) Si3N4-TiN layers. The residual stresses are controlled by the amount of TiN in layers with residual tensile stresses and the layers thickness. The fracture toughness of pure Si3N4(5wt%Y2O3+2wt%Al2O3) ceramics was measured to be of 5 MPa m1/2, while the apparent fracture toughness of Si3N4/Si3N4-TiN laminates was in the range of 7-8 MPa m1/2 depending on the composition and thickness of the layers.

Carbon nanofibers (CNF) are vapor grown carbon fibers grown catalytically from gaseous hydrocarbons using metallic catalyst particles. While this type of carbon fiber has been known for many years, only recently have composite properties been studied. Rules for composite synthesis teach that composite properties depend on several key parameters, including fiber-matrix interphase and fiber aspect ratio. Good adhesion between these fibers and matrix resins is essential for the performance of CNF based composites, so the mechanical properties of composites are strongly influenced by fiber surface morphology and chemistry. This work examines the fiber-matrix adhesion problem as influenced by CNF fiber surface area and surface energy, and the impact of aspect ratio on composite electrical properties.

Typical commercial and experimental oxide glass fibers are made from silicate melts, which have viscosities of log 2.5 to log 3.0 poise at the forming temperatures. But, strong fibers were recently also made from melts having viscosities of 0.5 to 2.0 poise, and a sharp melting point rather than a viscosity that gradually changes with temperature. This paper analyzes the various mechanisms of fiber formation, and proposes an answer to the apparent inconsistencies. In this context, the present paper bridges recent advances in the disciplines of advanced inorganic fibers [1], composite reinforcing fibers [2, 3, 4], and fiber glass reinforcements [5].

Rare-earth-aluminum oxide-composition glass fibers 5-50 μm in diameter and containing up to 50 mole % rare-earth oxide were drawn from undercooled liquids 550-650 K below the equilibrium melting point. The fibers have tensile strengths of ∼6 GPa, glass transition temperatures of ∼1150 K, and infrared transmission up to ∼5500 nm. The optical properties of erbium-doped fibers containing up to 12.5 mole % Er2O3 were investigated. The 1/e lifetime of the 4I13/2 excited state was 0.8-7 ms, decreasing with increasing Er concentration. Amplified spontaneous emission measurements indicate extremely broadband spectra, up to 135 nm (3-dB width) in 0.5 mole % fibers. Although this result is encouraging, the gain bandwidth, which has not been measured, is likely narrower. Glass fibers were crystallized by heat treatment under tension at temperatures of 1300-1900 K to form flexible, creep resistant polycrystalline monofilaments with tensile strengths up to 2.4 GPa.

Blends of styrene-maleic anhydride (SMAH) and polyethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) were produced in a batch mixer and in a corotating twin screw extruder. E-MA-GMA concentration was varied from 0 % to 50 %. Batch mixing indicated that the blend system was reactive. Extruded blends were characterized in terms of rheological, thermal and mechanical properties, and their morphology was observed. Rheological properties such as the storage modulus, loss modulus and complex viscosity exhibited maxima at 25 % EMA-GMA content. The blends had fine morphology as observed by scanning electron microscopy. Thermal properties were not significantly affected by the change in epoxy concentration. As E-MA-GMA concentration increased, tensile strength and modulus of elasticity decreased, but percent strain at break increased. These observations could be explained in terms of the chain extension / branching reactions that occurred in mixing the blends.

Keratin protein fiber (AKF™) is a renewable source of biosorbent that can be used for filtration of heavy metal and nanosize contaminants. The major composition of keratin fiber is the structured protein micofibril, consisting of numerous nanosized pores. The combination of nanostructure and metal binding capacity protein sites make it an ideal material for removal of heavy metals from solutions. The mechanism of heavy metal uptake onto keratin protein involves a combination of several steps such as adsorption, precipitation, and ion exchange. Keratin protein has good tensile strength and is stable over a wide pH range.

Available as agricultural resources in many countries, natural fibers, such as flax, hemp, kenaf, exhibit mechanical properties comparable to those of synthetic fibers like glass. But they are lighter, biodegradable, and are often claimed to be less expensive. Composites with these natural fibers have the potential to be attractive alternative to synthetic fiber composites. The natural fibers, however, exhibit more scatter in their properties, are thermally less stable and are sensitive to moisture absorption. The choice of matrix to reinforce with these fibers therefore becomes critical.

Currently, synthetic non-biodegradable polymers, such as polypropylene, polyester, etc., are being explored as matrix materials, for applications in sectors like automobiles and buildings. Biodegradable polymers, if made available in sufficient quantities at affordable prices, pave way for bio-composites in future. With both matrix and fibers being biodegradable, bio-composites become attractive candidates from the environment point of view.

Extensive and reliable property data on natural fiber composites and/or on bio-composites, are still lacking, making product design with these materials rather tedious. Once the database is available, design & manufacture of products with natural fiber composites and biocomposites offer several opportunities and challenges.

By reinforcing glass and glass-ceramic matrices with ceramic or metallic fibres, advanced composite materials with improved mechanical properties can be fabricated. These composites were originally developed as model systems for laboratory-scale experiments. Due to their remarkable thermomechanical properties, however, the materials are candidate for a variety of technical applications. The present contribution is based on an extensive review of the available literature on these materials, accumulated in the last 30 years, focusing on manufacturing techniques. The literature analysis reveals that several challenges related to the composites fabrication remain for future developments. In particular, it is shown that relative limited R&D work has been carried out so far in the area of manufacturing of engineering components and structures having complex geometry and large dimensions. The application of electrophoretic deposition techniques in order to manufacture three-dimensional components, e.g. tubes, may represent a considerable improvement in this regard. The final goal of this report is to generate a broader interest in glass and glass-ceramic matrix composites both in the scientific and industrial communities, so that the high technological potential of these materials can be wider exploited.

The tribological and mechanical properties of a novel polyamide 12 (PA12)/Al-Cu-Fe quasicrystal (QC) composite were systematically studied to accelerate efforts to develop a useful, melt-processable, and wear-resistant polymer composite. The wear and friction properties were characterized using a pin-on-disk configuration and the static and dynamic mechanical properties were investigated using dynamical mechanical analyzer, tensile tester, and an impact tester. Further, the melt processability of the composite was studied using a Haake torque rheometer and a dynamic rotational rheometer. The results suggest that PA12/QC composite can be melt-processed into a wear-resistant material with enhanced mechanical properties for applications where combinations of wear resistance and good mechanical properties are required. The static mechanical properties of the composite were found to be consistent with the Halpin-Tsai equation and agreement was observed between the measured viscoelastic properties and theoretical predictions of Burgers' and Eilers' models.