Synthetic fiber reinforced composites offer excellent mechanical properties and performance. However, due to the environment awareness and the growing requirement for fuel economy there is a growing urgency for combining a polymer with natural materials to create an eco-friendly composite that is also light-weight and low cost. This research investigates multiple ways of using cellulose fibers in applications ranging from composites for automotive applications to their use on electronic devices, so the broad potential of cellulose can be exploited.The first investigation involves adding cellulose nanocrystals (CNCs) to a conventional carbon fiber-epoxy composite to simultaneously strengthen and toughen the composite. CNCs were functionalized with 3-aminopropyltriethoxysilane (APTES) and distributed at the interphase between a carbon fiber (CF) and an epoxy matrix. Stronger fiber/matrix adhesion was achieved by sizing CFs with a layer of epoxy, and further increase in interfacial shear strength (IFSS) was achieved by adding the functionalized CNCs (APTES-CNCs) at the interphase. Sizing CFs with APTES-CNCs at a concentration of 1.0 wt% resulted in 81% increase in IFSS compared to unsized CFs due to the establishment of covalent bonding and the stiffness of the interphase modulus.Cellulose fibers were investigated at the macro scale when combined with inorganic reinforcements (glass fiber or talc) in a hybrid composite. Hybrid composites were injected molded with total fiber content kept constant at 30 wt% and the properties of the composites were characterized over 0-30 wt% of cellulose in a polypropylene (PP) matrix. Tensile, flexural and notched Izod impact tests revealed that in general the mechanical properties decreased with increasing cellulose content. The crystallization temperature (Tc) of the composites increased compared to neat PP, revealing the fibers ability to act as nucleating agents and speed rate of part production which will result in lowering the manufacturing cost. Overall, combining an optimum concentration of cellulose fiber with glass or talc is a promising alternative to reduce or replace the use of inorganic reinforcements on automotive under-the-hood and body interior components.The use of cellulose fiber in electronic devices was investigated. Sensors to detect ultraviolet (UV) radiation were fabricated on a rigid glass substrate as well as on flexible substrates composed of cellulose fiber in the form of a paper or a polyimide film (PI). Carbon Nanotubes (CNTs) were drop-cast between the electrodes of the sensor on each substrate. All sensors respond immediately to UV On/Off cycles with a change in resistance due to the ability of CNTs to adsorb and desorb oxygen on their surface. Although the PI substrate yielded a sensor with the greater response, the cellulose paper proved to be effective to detect UV radiation, keeping its functionality even after being mechanically bent 1000 times, which is an advantage for practical applications.The final project investigated the use of bamboo fibers (BFs) as the main reinforcement in a high-fiber volume fraction composite. Unidirectional long BF reinforced epoxy composites were made by compression molding and a process to surface treat the BF with sodium hydroxide (NaOH) was performed. Composites with 40v% NaOH modified BFs show a considerable increase of 29% for flexural modulus and 26% for flexural strength, compared to 40v% untreated BF reinforced composites. Coating the NaOH modified BF with Graphene Oxide (GO) resulted in composites with greater flexural properties, increasing modulus at 43% and strength at 29%.This research has explored using cellulose fibers at both the nano and macro scales as an addition to synthetic fibers and also as a potential ecofriendly alternative to replace synthetic fiber in reinforced composites.
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