Optimal temperature and current cycles for curing of composites using embedded resistive heating elements

Curing is an important and time consuming step in the fabrication of thermosettingmatrix composite products. The use of embedded resistive heating elements providing supplemental heating from within the material being cured has been shown in previous studies (Ramakrishnan, Zhu, and Pitchumani, 2000, J. Manuf. Sci. Eng., 122, pp. 124-131;, Compos. Sci. Technol., 60, 2699-271

Curing of composites using internal resistive heating.

Curing of fiber-resin mixtures is often the critical and productivity controlling step i

Fibre Distribution and the Process-Property Dilemma

The options for the fibre reinforcement of polymer matrix composites cover a range from short-fibre chopped strand mat, through woven fabric to unidirectional pre-impregnated (prepreg) reinforcements. The modelling of such materials may be simplified by assumptions such as perfect regular packing of fibres and the total absence of fibre waviness. However, these and other features such as the crimp or waviness in woven fabrics make real materials more complex than the simplified models. Clustering of fibres creates fibre-rich and resin-rich volumes (FRV and RRV respectively) in the composites. Prior to impregnation, large RRV will be pore-space that can expedite the flow of resin in liquid composite moulding processes (especially resin transfer moulding (RTM) and resin infusion under flexible tooling (RIFT). In the composite, the clustering of fibres tends to reduce the mechanical properties. The use of image processing and analysis can permit micro-/meso-structural characterisation which may correlate to the respective properties. This chapter considers the quantification of microstructure images in the context of the process-property dilemma for woven carbon-fibre reinforced composites with the aim of increasing understanding of the balance between processability and mechanical performance

A Review on the Mechanical Modeling of Composite Manufacturing Processes

© 2016, The Author(s). The increased usage of fiber reinforced polymer composites in load bearing applications requires a detailed understanding of the process induced residual stresses and their effect on the shape distortions. This is utmost necessary in order to have more reliable composite manufacturing since the residual stresses alter the internal stress level of the composite part during the service life and the residual shape distortions may lead to not meeting the desired geometrical tolerances. The occurrence of residual stresses during the manufacturing process inherently contains diverse interactions between the involved physical phenomena mainly related to material flow, heat transfer and polymerization or crystallization. Development of numerical process models is required for virtual design and optimization of the composite manufacturing process which avoids the expensive trial-and-error based approaches. The process models as well as applications focusing on the prediction of residual stresses and shape distortions taking place in composite manufacturing are discussed in this study. The applications on both thermoset and thermoplastic based composites are reviewed in detail

Electrocatalysis by microelectrodeposits

Glassy carbon disc electrodes were used to deposit micro quantities of Pt and Pd catalysts. Voltammetric studies were made to examine the hydrogen adsorption and oxygen reduction on these model catalysts. Their electrocatalytic activity towards anodic oxidation of methanol, formaldehyde and ethylene glycol in acid and alkaline medium is dependent upon the amount of deposits, their hydrogen adsorption properties and crystaUite parameters

Aerosol assisted synthesis of nanostructured silica

Zeolites are microporous aluminosilicates that have broad applications especially in industrial processes like fluidized catalytic cracking (FCC) owing to their unique properties with respect to both activity and selectivity. However, the micropores of zeolites may in some cases limit their catalytic performance due to restricted molecular transport induced by similar size of the diffusing hydrocarbons and the micropore size. This had led researchers to develop mesoporous silica materials (pore sizes in the range of 2 and 50 nm) as catalyst supports for enhanced molecular transport. Mesoporous silica are usually prepared using the conventional sol-gel synthesis which takes several days and the final morphology is often irregular. The present thesis deals with the use of a continuous aerosol reactor process involving evaporation induced self-assembly (EISA) that allows synthesis of mesoporous silica (using a tri-block co-polymer, P123 as a templating agent) within several seconds. The synthesis in general involves a large number of experimental parameters. In order to explore this high dimensional experimental space, a factorial design of experiments was employed to study the effect of important variables, namely the precursor composition and the tubular reactor temperature, on the textural properties of the final product. This methodology allows simultaneous investigation of the influence of multiple parameters, which is advantageous over the traditional form of experimentation in the nanomaterials community, where only one variable is changed at a time. It allows exploration over a wider range of conditions to highlight the true nature (global/local) of trends that are often misinterpreted as a universal occurrence in conventional experimental trials. Using contours, this method exclusively determined multiple conditions for achieving a required surface area and pore volume. It also illustrated the variation of these properties over a wider domain of experimental conditions. Additionally, novel mesoporous silica and silica-alumina materials were synthesized using a laboratory spray drier by self-assembly of nanosized silica and alumina particles, using P123 as a structure directing agent. The materials possessed extraordinary steam stability and showed good potential when their performance was tested in pulse cracking experiments. The method offers exciting opportunities for further industrial development as part of mesoporous zeolite composites.Applied Science

Breakage Characteristics of Particles and Granules

Applied Science