Low-cost hybrid polyurethane/natural fibers composites were developed and characterized in terms of elastic modulus, resilience, permanent deformation in compression test, and ash content. Composites manufactured in the form of foams were made with partial replacement of 10% (w/w) of polyethylene glycol by natural fibers from rice husk (R.H.), cassava bagasse (C.B.) and wood fiber (W.F.). Composites containing untreated fibers and mercerized fibers were also developed. A simplex-centroid mixture model was used for statistical analysis of the effects caused by the addition of the fibers. Based on the complete cubic model considering all the interactions, it was possible to obtain the common optimum, regarding all the properties studied. For hybrid composites with natural fibers, the optimal composition is 4.5% of C.B. and 95.49% of W.F. while for composites with mercerized fibers is 39.24% of R.H., 26.30% of C.B., and 34.46% of W.F.
An alkaline free-of-cyanide electrodeposition solution using sorbitol as complexing agent was employed for obtaining metal-matrix-composite coatings of CuZn-Al 2 O 3 . These coatings consisted of CuZn as metal matrix and hard micrometric alumina (Al 2 O 3 ) particles as the dispersed phase. These composite coatings could be employed in protection of metallic pieces subjected to erosion-corrosion, since they will combine corrosion resistance of the CuZn matrix and mechanical resistance given by the hard Al 2 O 3 particles. It is shown that these coatings could be obtained from the proposed solution, but only in high electrodeposition cathodic current densities (i g ), for ½i g ½> 15 mAcm -2 . Vickers microhardness (MH) of the composite coatings was significantly increased when comparing with pure CuZn coatings for i g . The increased microhardness is due to occluded Al 2 O 3 , since it was not observed grain refinement due to Al 2 O 3 . Based on these results, CuZn-Al 2 O 3 composite coatings have prospects for erosion-corrosion protection.
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