Robb M. Winter

Sample preparation techniques for nano-mechanical characterization of glass fiber reinforced polyester matrix composites

Abstract Glass fiber reinforced plastics are widely used in a host of engineering applications. In these two component materials, the region around the boundary where the components meet is known as the ‘interphase’. The size of the interphase is typically of the order of few microns and understanding the mechanical properties of this microscopic region is central to understanding the mechanical behavior of the composite. Such a small region is amenable to nanomechanical investigation using nanoindentation techniques. For nano length scale investigation it is imperative to have a surface with a roughness of the order of 10s of nanometers. In this investigation techniques have been developed to obtain very low surface roughness in both monolithic polyester and glass fiber reinforced polyester composite samples using a combination of abrasion and etching.

Investigation of Nanomechanical Properties of the Interphase in a Glass Fiber Reinforced Polyester Composite Using Nanoindentation

Glass fiber reinforced polymer composites are widely used as structural materials. These two-component materials can be tailored to suit a large variety of applications. A better understanding of the properties of the fiber-matrix ‘‘interphase’’ can facilitate optimum design of the composite structure. The interphase is a microscopic region around the fiber and hence nano-scale investigation using nano-indentation techniques is appropriate to determine mechanical property variations within this region. In this study the atomic force microscope adapted with a commercial nanoindenter has been used to determine the variation of the elastic modulus across the interphase for different silane coated glass fiber reinforced polyester matrix composites. A comparative study of the elastic modulus variation in the various interphases is reported. The results are discussed in the light of the current limitations of the instrumentation and analysis.@DOI: 10.1115/1.1543966#

Determination of As, Cd, Cr, and Pb Species Formed in a Combustion Environment

Abstract To facilitate the understanding of the fate of metals during incineration the speciation of metals is critical. Thus, an experimental study to determine the speciation of metals during incineration was performed. Aqueous metal salts of arsenic, cadmium, chromium, and lead were injected into a laboratory reactor, post-flame. Aerosols were captured on a glass fiber filter by isokinetic sampling. Reactor temperature was varied from 600 to 1100°C and the stoichiometric ratio was varied from 0.95 to 1.25. The Reference Intensity Method (RIM) of quantitative X-ray diffraction analysis combined with X-ray transmission was utilized to determine the speciation of aerosols removed from the combustion environment. The results indicate that temperature and stoichiometric ratio affect the formation of crystalline compounds in the combustion environment. Injection of different compounds of the same metal into the furnace resulted in the formation of different products. RIM was used to determine the composition...

In Situ Near-IR Cure Monitoring of a Model Epoxy Matrix Composite

To improve the performance of composites it is imperative that the interphase region between the inorganic reinforcement and the polymer matrix be more completely understood. It is in this region that the stress transfer between the matrix and the reinforcement occurs. To this end, the curing of epoxy adjacent to an embedded silica optical fiber has been monitored in situ by evanescent wave spectroscopy. The epoxy studied is partially fluorinated and has a lower refractive index than the silica optical fiber. This combination of epoxy/silica served as a model composite system. The lower refractive index of the partially fluorinated epoxy allowed the silica optical fiber to be used as a waveguide for the internal reflection of near-infrared light. The epoxy curing was determined as a function of time and temperature by analysis of the near-infrared spectrum from the epoxy adjacent to the fiber obtained by the interaction of the evanescent wave that occurs at each internal reflection with the low-refractive-index epoxy. The results obtained from the examination of the near-infrared spectrum, particularly the disappearance of the NH2 stretching/bending combination band at ∼4925 cm−1 and the concomitant increase of the C–N overtone band at ∼4725 cm−1, showed that epoxy ring-opening and cross-linking reactions could be followed in real time. Finally, treatment of the fiber with a silane coupling agent had no observable effect on the curing reaction of the epoxy.

Direct monitoring of silane/epoxy interphase chemistry

Abstract Evanescent wave spectroscopy has been used to directly monitor the interactions between an epoxy resin and an amino silane coupling agent, γ-aminopropyltrimethoxy silane (γ-APS) adsorbed on silica fibers. First, it was shown that reactions of the adsorbed silane molecules could be monitored as a function of drying at elevated temperature. Next, the silane surface treated fibers were embedded in the epoxy resin and the primary amine reactivity of the silane at 70°C was measured by the decrease from the initial absorbance height of the combination band at 4925 cm −1 . It was found that there was a decrease of 13% in band absorbance when the silane was adsorbed from a 5% γ-APS solution. The percent decrease was 22% and 38% when the silane was adsorbed from 2% and 1% γ-APS solutions, respectively. The results show that a significant fraction of the amine groups remain unreacted, even in the presence of excess epoxy. Also, it was discovered that in no instance was there any indication of silane diffusion from the interphase during the course of the experiment, even when the adsorbed silane was not dried at elevated temperature, prior to placement in the epoxy resin.

Rate limiting processes in the rotary-kiln incineration of contaminated solids

Abstract A study of transport processes during the desorption of organic and metallic contaminants from solids is being conducted using several fundamental experiments. This paper presents results from three experimental systems, a Particle-Characterization Reactor, Bed-Characterization Reactor, and Metals Reactor. The organic experiments attempt to identify the controlling transport process within a particle of soil and through a bed of particles, as well as quantify the necessary parameters to model these processes. Gas and solid-phase speciation data for field samples, soils contaminated with a variety of organics (boiling points from 220°C to 495°C), are discussed. The data suggest that local temperature and gas/solid contacting are important in the desorption process. As expected, lighter components desorb faster than the heavier hydrocarbons. Moisture content was also important in the desorption of contaminant. The metals reactor has been used to determine the fate of metals, specifically the partit...

Evanescent wave spectroscopy for in-situ cure monitoring

The curing of epoxy adjacent an embedded silica fiber has been monitored in situ by evanescent wave spectroscopy. The epoxy studied is partially fluorinated and has a lower refractive index than the silica optical fiber. This lower refractive index allows the silica optical fiber to be used as a waveguide for the internal reflection of near-infrared light. The curing agent was polyoxypropylenediamine. The epoxy curing was monitored as a function of time by analysis of the near-infrared spectra of the epoxy/curing agent adjacent the fiber. The results obtained from the examination of the near-infrared spectra, particularly the disappearance of the primary N-H stretching/bending combination band at approximately 4935 cm-1 and the accompanying increase of the C-N overtone band at approximately 4650 cm-1, showed that the epoxy curing reaction could be followed in real time using an 85 micron diameter silica optical fiber bundle. It was found that the primary amine groups are essentially completely reacted after 60 minutes.

FT-IR/ATR AND SEM STUDY OF COLLOIDAL PARTICLE DEPOSITION

Abstract Fourier transform infrared attenuated total reflectance (FT-IR/ATR) spectroscopy and scanning electron microscopy (SEM) have been used to study the deposition of 406 nm diameter amidine functionalized latex particles at silica surfaces at pH 6.6 and 22.0. SEM micrographs were used to determine the area fraction of the surface covered by latex particles as a function of solution concentration and time. At pH 10.6 no deposition was observed. At pH 6.6 the maximum coverage reached at all concentrations was approximately 48% and the time necessary to reach the maximum coverage increased with decreasing concentration of latex particles. The deposited latex particles were not removed from the surface by removing the latex particles from solution and increasing the pH from 6.6 to 10.6. These results are in agreement with the expected deposition mechanism. For the FT-IR/ATR results fused silica ATR elements were used. These crystals exhibit a window in the mid-IR between 3100 and 2800 wavenumbers. The latex particles have several bonds which absorb IR light in this frequency range. The absorbance of the asymmetric –CH 2 stretching band of the polystyrene latex was chosen to follow the deposition kinetics. The kinetics of deposition followed in this manner were similar to the deposition studied by SEM. In particular, the final surface coverage was equivalent in both cases. However, the time taken to reach the maximum was slightly greater for the FT-IR/ATR experiments. Finally, the maximum coverage was used to determine the interparticle spacing and hence the interaction distance of the overlapping double layers between particles. The maximum coverage expected for noninteracting particles is 54.7% if the random sequential adsorption (RSA) model is used or 61.1% if ballistic deposition is active. The average distance between particles was found to be 2.6 times the Debye length assuming RSA and 5.2 times the Debye length assuming ballistic deposition. This seems to indicate that ballistic deposition is occurring in the system studied.

Data analysis and optimal specification of fuse model for fault study in power systems

In order to study the thermal energy in the process of fuse melting, data analysis is conducted on the time/current curve provided by the manufacturer. Data analysis methodologies, such as sampling, variance analyze and residual sum of squares analyze, are performed in this process. These methods provide us the most optimal equation to describe the relationship between time, different level of fault current and the thermal energy that melts the fuse. A simulation fuse model is developed based on this result, and this model is tested in both DC and AC environment for verification purposes.

Modeling and control architecture of source and load management in islanded power systems

This paper studies the power consumption and supply in an islanded power system (IPS) with high penetration of air conditioning load. The characteristics and behaviors of the loads in the IPS are researched and analyzed. Based on the power study, a new source and load management (SLM) system is designed to improve the power quality and energy/fuel efficiency in the power systems. In this paper, at first, an indoor temperature model with a parameter identification tool is constructed to help us analyze the power demand of heating, ventilation, and air conditioning (HVAC) loads, which plays an important role in IPS power study. Then, a baseline model of a typical IPS is built to consider the power consumption in the whole power network. Based on the baseline model, we assign a priority to each power demand, and propose the control architecture and strategy of the SLM. The control performance is validated by simulation tests to demonstrate the effectiveness on the energy and fuel efficiency improvement as well as maximized comfort indoor.