Curing of Composites Using Internal Resistive Heating

1999 ◽  
Vol 122 (1) ◽  
pp. 124-131 ◽  
Author(s):  
B. Ramakrishnan ◽  
L. Zhu ◽  
R. Pitchumani

Curing of fiber-resin mixtures is often the critical and productivity controlling step in the fabrication of thermosetting-matrix composites. The long processing times (and costs) have remained the fundamental impediment to widespread commercialization of composites. Shortening the cure cycle time, while ensuring a complete and uniform cure in the product, is imperative for realizing the goal of affordable materials processing, and forms the focus of this investigation. Toward addressing the affordability challenge, this paper explores the use of conductive carbon mats embedded inside the composite as a means of providing internal volumetric resistance heating during the cure process. The supplemental heating results in temperature and cure uniformity through the cross section, as well as speeds up the cure process. In the context of application to resin transfer molding, systematic experimental and theoretical studies on various resistive heating configurations are presented. Optimum processing strategies are derived based on the cure time and microstructural product quality considerations. [S1087-1357(00)01101-1]

2020 ◽  
Author(s):  
Thomas Louis-Goff ◽  
Huu Vinh Trinh ◽  
Eileen Chen ◽  
Arnold L. Rheingold ◽  
Christian Ehm ◽  
...  

A new, efficient, catalytic difluorocarbenation of olefins to give 1,1-difluorocyclopropanes is presented. The catalyst, an organobismuth complex, uses TMSCF<sub>3</sub> as a stoichiometric difluorocarbene source. We demonstrate both the viability and robustness of this reaction over a wide range of alkenes and alkynes, including electron-poor alkenes, to generate the corresponding 1,1-difluorocyclopropanes and 1,1-difluorocyclopropenes. Ease of catalyst recovery from the reaction mixture is another attractive feature of this method. In depth experimental and theoretical studies showed that the key difluorocarbene-generating step proceeds through a bismuth non-redox synchronous mechanism generating a highly reactive free CF<sub>2</sub> in an endergonic pre-equilibrium. It is the reversibility when generating the difluorocarbene that accounts for the high selectivity, while minimizing CF<sub>2</sub>-recombination side-reactions.


Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy

This chapter presents experimental studies performed on planar semiconductor microcavities in the strong-coupling regime. The first section reviews linear experiments performed in the 1990s that evidence the linear optical properties of cavity exciton-polaritons. The chapter is then focused on experimental and theoretical studies of resonantly excited microcavity emission. We mainly describe experimental configuations in which stimulated scattering was observed due to formation of a dynamical condensate of polaritons. Pump-probe and cw experiments are described in addition. Dressing of the polariton dispersion and bistability of the polariton system due to inter-condensate interactions are discussed. The semiclassical and the quantum theories of these effects are presented and their results analysed. The potential for realization of devices is also discussed.


1989 ◽  
Vol 28 (13) ◽  
pp. 2552-2560 ◽  
Author(s):  
Claudio Bianchini ◽  
Franco Laschi ◽  
Dante Masi ◽  
Carlo Mealli ◽  
Andrea Meli ◽  
...  

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