A novel fibre treatment recently proposed in the literature was optimised in the case of woven jute fabric/vinylester laminates to obtain the best tensile properties. It consists on an alkali treatment superimposed to biaxial tensile stress. Optimisation was performed by changing the treatment time. The novel fibre treatment was compared with traditional chemical methods. Tensile properties exhibited a maximum with the treatment time at 4 h due to the less efficient period of time and to the excessive fibre damage for times shorter and longer than 4 h, respectively. All composites with fibres treated with alkali under stress exhibited improved tensile strength in comparison with the composites with untreated fibres or with fibres treated with traditional methods due to the better interfacial properties and the structural changes of the fibres promoted by the novel treatment. Stiffness values were only higher for the composite with fibres treated with alkali under stress for 4 h, probably in correspondence with a maximum in the stiffness of the individual fibres.Fil: Vázquez, Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Stocchi, Ariel Leonardo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Grupo de Materiales Avanzados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bernal, Celina Raquel. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Grupo de Materiales Avanzados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina