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SynopsisAverage advancing and receding contact angles made against cotton and glass fibers by a set of probe liquids are determined using the Wilhelmy technique. The dispersive and polar components of the surface energy are calculated from the measured contact angles using both the geometric and the harmonic mean methods. It is found,that these components are Simiiar for untreated cellulose and glass fibers, and that they both have a high polar component, corresponding to a hydrophilic surface. Changes in surface energy caused by treatment of the cellulose fiber surfaces with melamine, polyethyleneimine (PEI), and a silane coupling agent are reported. It is found in particular that polyethyleneimine treatment of cellulose significantly reduces the polar component of its surface energy. While treatment of glass fibers with a silane coupling agent reduces the polar component and increases the dispersive component of the surface energy, it shows little effect on the surface energy of cellulose.

The objective of this paper is to review and recast previous analytical approaches to the analysis of the elastic stiffnesses of corrugated core sandwich panels into the framework of first-order shear deformation laminated plate theory. Extensional, shear and bending stiffnesses will be determined and compared to measured data. It is shown that the in-plane extensional and shear stiffness and the bending and twisting stiffnesses are dominated by the face sheets and that calculated values agree with measured data. Transverse shear stiffnesses, however, are highly dependent on the integrity and shape of the core and the details of face-to-core bonding, and predictions were found to be highly unconservative. A major factor for the reduction in stiffnesses of the core is attributed to delamination damage of the web inflicted during the corrugation process.

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SynopsisDry-formed networks of cellulose fibers, produced with a laboratory device, have been impregnated with aqueous solutions of poly(viny1 alcohol) or solutions of poly(viny1 acetate) in acetone. In both cases, the strength and stiffness of the networks increase several times compared with the unmodified structure. When aqueous solutions are used, it appears that a minimum amount of poly(viny1 alcohol) is required (ca. 2 wt %) to increase the strength appreciably, but when poly(viny1 acetate) dissolved in acetone is used, as a binder, the strength improves even at the lowest level of polymer addition. For the systems studied here, the elongation at rupture increased with increasing polymer concentration. In most cases, the amount of polymer in the network structure was less than 10 wt %. Some results from impregnations using other polymeric systems, e.g., latices, are also reported.