The objective of this work was to analyze the influence of the alkalization and alkalization + silanization (mixed) treatments on the interfacial adhesion and mechanical properties of intralaminar hybrid composites (jute + sisal, jute + curauá, jute + ramie, and jute + glass fiber). Single‐fiber tensile tests, fragmentation, and short beam tests were performed. Finally, a SEM analysis was used to study the influence of surface chemical treatments on the morphology of the natural fibers used. SEM images showed that the chemical treatments altered the morphology of the natural fibers. The chemical treatments improved the tensile strength of the fibers studied. It was found that the alkaline treatment is the best suited for jute, ramie, and curauá fibers, while the sisal fiber presented the best results after the mixed treatment. The superficial chemical treatments also affect the interfacial/interlaminar adhesion of the hybrid composites studied here. The best superficial treatments for each type of hybrid composite were: alkaline treatment for jute + ramie and jute + sisal, while for jute + curauá the best results were obtained for the untreated specimens.

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This paper presents the adhesive strength of FeCr and FeCoCr coatings produced by electric arc thermal spray process on carbon steel plates. Carbon steels are not resistant to corrosion and several methods are used in surface engineering to protect them from aggressive environments such as the marine one. The main objective of this work is the evaluation of the mechanical and metallurgical properties of coatings produced by thermal spray on carbon steel. Five chemical compositions were tested in order to give a large panel of possibility. Coatings were characterized by several methods to result in a screening of performance. The physical properties of coatings were also evaluated by adhesion quantification, using pull-off test, and microhardness measurement. The assessment of microstructural morphology by X-ray diffraction (XRD) and scanning electron microscopy (SEM) was made. The open circuit potential was monitored to evaluate the corrosion tendency. SEM results showed uniformity in the deposited layer and low amount of oxide and porosity. The adhesive strength of FeCoCr alloy coatings was higher than other coating conditions. In the immersion test, all sealed conditions presented high

ResumoThe results show that it is possible to achieve adequate mechanical properties for all analyzed conditions. Furthermore, it was observed that the productivity provided by the gas metal arc welding process was greater than shield metal arc welding. Key-words:HY-80 steel, mechanical properties, post weld heat treatment. IntroduçãoAs estruturas de navios e submersíveis são submetidas à carregamentos dinâmicos complexos durante o serviço os quais são agravados pelas tensões residuais presentes resultantes dos processos de fabricação. Desta forma, aços de alta performance para estas estruturas tem sido uma busca constante pela Marinha Americana. De forma a possibilitar o atendimento dos requisitos de alta resistência e boa tenacidade a baixa temperatura, são utilizados os aços das famílias "High Yield Strength Steels" (HY) e alta resistência e baixa liga (ARBL) desenvolvidos nos últimos 50 anos pela Marinha Americana [1].Os aços da família HY são aços baixa liga do tipo temperado e revenido, contendo teor de carbono entre 0,12 e 0,20% e um teor total de elementos de liga de aproximadamente 8%. Desta forma, eles propiciam boa temperabilidade para formação de martensita de alta resistência, mesmo em grandes espessuras e boa tenacidade após o revenimento. Para melhoria da tenacidade dos aços HY, o elemento níquel é adicionado como o principal

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