High performance bio-based composites : mechanical and environmental durability

• Main Author: Doroudgarian, Newsha
• Other Authors: Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Luleå tekniska universitet, Anglada Gomila, Marcos Juan, Joffe, Roberts
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universitat Politècnica de Catalunya 2016
• Subjects: Àrees temàtiques de la UPC::Enginyeria dels materials; Luleå
• Online Access: http://hdl.handle.net/2117/96308; http://hdl.handle.net/10803/392719; https://doi.org/10.5821/dissertation-2117-96308

Cotutela Universitat Politècnica de Catalunya i Luleå tekniska universitet http://pure.ltu.se/portal/en/publications/high-performance-biobased-composites(9f34c277-ced2-4332-aaf0-22e09c997264).html The presented work is a part of the ongoing effort on the development of high performance bio-based composites with enhanced durability, under static and dynamic mechanical loading including the exposure to elevated humidity. The impact of relative humidity on the performance of cellulosic fibers (natural and regenerated), bio-based resins and their composites was studied. The material performance was rated against the data for glass fiber epoxy, as the reference. The comparison of water absorption results for unreinforced resins and for composites showed that the cellulosic reinforcement is primarily responsible for the transport and uptake of moisture in the composites. The effect of chemical treatment on the cellulosic fibers, as a protection against moisture, was evaluated. However, the treatment did not improve the moisture resistance in composites significantly. Quasi-static tensile tests revealed that some of the bio-based resins and their composites performed very well and comparable to the composites of synthetic epoxy, even at high humidity. However, any structural material is supposed to hold mechanical loads over a long service time and most often in harsh environmental conditions. Hence, tension-tension fatigue tests were performed on the fiber bundles as well as on the composites. The fibers of choice as the reinforcement for further mechanical testing were regenerated cellulose fibers (RCF), mainly owing to the stable geometry and properties. Due to the high nonlinearity of RCF, the fatigue tests were limited in number and the focus was on analyzing the mechanisms underlying the fatigue behavior rather than on constructing S-N curves. Strain evolution of the bio-based composites during the dynamic fatigue was very similar to that observed in the static fatigue (creep). It confirmed the strong ...