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ABSTRACT:The bond strengths of polymer concretes containing up to 15% (based on polymer resin) of diacrylate (DA) monomers were examined and compared with those without DA. A change occurring with the addition of DA monomers was an increase in the bond strength of polymer concrete to wet substrates. Zinc diacrylate (ZDA) and calcium diacrylate (CDA) were each used as an additive to monomers and resins [methyl methacrylate (MMA), polyester, and two kinds of epoxies]. The variables were amount of the DA monomers and surface conditions (wet or dry and smooth or rough). Bond strengths were measured by tension bond. ZDA was found to improve the bond strength of MMA and polyester, whereas CDA improved the bond strength of epoxies.

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This paper presents a general analytical model for free vibration of thin-walled composite beams with arbitrary laminate stacking sequences and studies the effects of shear deformation over the natural frequencies. This model is based on the first-order shear-deformable beam theory and accounts for all the structural coupling coming from the material anisotropy. The seven governing differential equations for coupled flexural-torsional-shearing vibration are derived from the Hamilton's principle. The resulting coupling is referred to as sixfold coupled vibration. Numerical results are obtained to investigate the effects of fiber angle, span-toheight ratio, modulus ratio, and boundary conditions on the natural frequencies as well as corresponding mode shapes of thin-walled composite box beams.Keywords: Thin-walled composite beams; shear deformation; sixfold coupled vibrations. * Professor, corresponding author. Tel.: +82-2-3408-3287; Fax: +82-2-3408-3331.