Design of a single layer micro-perforated sound absorber by finite element analysis

Micro-perforated sound absorbers with sub-millimeter size holes can provide high absorption coefficients. This paper presents results of work on the development of an effective single layer micro-perforated sound absorber from the commercial composite material Parabeam^® with micro diameter holes drilled on one side. Parabeam^® is used as a structural material made from a fabric woven out of a E-glass yarn and consists of two decklayers bonded together by vertical piles in a sandwich structure with piles (thick fibers) woven into the decklayers. The paper includes, the analytical model developed for prediction of absorption coefficients, finite element solution using commercial software MSC.ACTRAN and experimental results obtained from impedance tube measurements. A simple optimization is performed based on the developed models to obtain an efficient absorber configuration. It has been anticipated that several different and interesting applications can be deduced by combining structural and sound absorption properties of this new micro-perforated absorber.     

Bifunctional Initiators: Synthesis,Characterization, and Initiator Properties of Azo-Benzoin Initiators

Two new azo-benzoin initiators were synthesized by the condensation of 4,4′-azo-bis-(4-cyanopentanoic acid chloride) (ACPC) with benzoin (B) and α-methylolbenzoin methyl ether. The initiator structures were confirmed by IR and NMR spectroscopy. The kinetics of the bulk polymerization of styrene initiated by the azo benzoin initiator, obtained from ACPC and B, was investigated and the kinetic parameters evaluated. The initiation of polymerization of styrene by means of azo-benzoin initiators yields polymers with terminal photoactive benzoin groups.