As described in Chapter 1, hydrokinetic technology has attracted a lot of interest as a sustainable energy generation alternative, especially in places where conventional hydropower technology isn't practicable. The blade is the most i mportant part of a hydrokinetic turbine. It is engineered using hydrodynamic science to extract the maximum amount of energy and is expected to bear high loading for extended periods. The material selection for the hydrokinetic turbine blades is important in such a severe environment. Chapter two reviews composites for the manufacture of hydro kinetic turbine blades. The forces on the hydrokinetic turbine blade and the composite materials that can withstand these loads are discussed in this chapter. Finally, the constraints and opportunities of composites for hydrokinetic turbine blades with good performance and endurance are recommended. As a sustainable alternative to human- made fibers for composites, Chapter 3 investigates for the first time the mechanical properties of single fibers of Yushania alpine (highland bamboo) which is an Ethiopian indigenous species. This lack of information is a serious l imitation on their application. This work fills information gaps to prepare for the growing usage of Ethiopian bamboo in a variety of applications. In chapter four subsection one, untreated Ethiopian highland bamboo fibers are characterized and the optimal properties are determined. In the investigation , scanning electron microscopy (SEM) was applied to examine the surface texture of the fibers. The chemical bonds of the molecules (functional groups) were identified by Fourier transform infrared spectra. The thermal properties of the fiber were explored with a thermo gravimetric analyzer, and the results were confirmed by differential thermo- gravimetric analysis (DTG). Mechanical properties were improved using the experimental design principle. The design is based on the response surface meth odology (RSM) three- factor three- level mathematical models. At various plant ages, the properties were found for varying culm wall thickness in the radial direction and soaking duration of the single fiber extracted using a roller crusher machine. The operating parameters and optimal mechanical properties were validated using confirmation tests. Breaking force 796.5cN, tenacity 46.8cNtex -1 , work done 456cNmm, and modulus 1814cNtex -1 were the optimal mechanical characteristics achieved at 2.0 years of age, a cu lm thickness layer coded values of 0.6 along the radial direction, and 3.8 days soaking time when compared to the mechanical properties over 1 to 3 years plant age, cu lm thickness layers of from primary (- 1) to Outer layers (1) along with the radial direction, and 3 to 9 days soaking time. ix Section two of Chapter Four examines the characterization and optimization of Y. alpina bamboo fiber characteristics extracted both chemically and mechanically. RSM was used to optimize mechanical properties and find linear, quadratic, and interaction of independent factors. Samples of length 25 – 30 cm were harvested at various ages from the middle of the stem which was then soaked in different NaOH concentrations for different times. Using a rolling machine that h as three rollers, the fiber was mechanically extracted. The optimal mechanical properties were observed at 1.8 years age, alkali concentration of 10%, and a soaking duration of 2.0 days. The optimal values at these variables of breaking force, elongation, tenacity, work done, and modulus is 777.8cN, 2.0%, 45.7cNtex −1 , 516.3cNmm, and 1969cNtex −1 , respectively, according to the BBD results. The model is significant (p ≤ 0.005) with a 95% confidence level for predicted values that were close to the measured values, indicating that the model's fit to the measured properties was strong at the optimized values. The optimized age and soaking duration ware subjected to chemical, thermal and morphological analysis for each corresponding NaOH Concentration (6%, 12%, and 18%) levels. SEM was employed to examine the microstructure of the fibers. It was discovered that the 18% NaOH treated fiber resulted in more wrinkles in the surface of bamboo fibers when compared with the 6% and 12% NaOH Bamboo fiber. thermogravimetric analysis and DTG found that weight loss increased as concentration increased but the scenario functioned for proper concentration. In Chapter four subsection Three, the morphological features, mechanical, and physical properties of sing le- layer unidirectional reinforcements were investigated for the manufacture of hydrokinetic turbine blades. The reinforcements included glass fiber, treated and untreated highland bamboo fiber, reinforced polyester- based composites and their hybrid composites, as well as row bamboo (bamboo culm). To make hybrid composite materials, different fiber types were combined with polyester resin in the ratios of fiber/matrix (30%/70%) and bamboo fiber/glass fiber (50%/50%). In comparison to materials reinforced with alkali - treated and untreated highland bamboo fiber reinforced composites, the flexural strength of the composite with glass fiber is increased by 12% and 21%, respectively. The alkali treatment of highland bamboo fiber improved its physical - mechanical properties, making it suitable for use in many application s. Alkaline treatment boosts the tensile and compressive strength by 37% and 3.4% for composite reinforced with untreated bamboo fiber, and 10.2% and 23.8% for composite reinforced with glass fiber, respectively. The fiber density of highland bamboo was increased by removing less dense non- cellulosic components (hemicellulose and lignin). However, the fiber's moisture absorption is the main issue in using it in a composite submerged in water. x This study investigated whether incorporating glass fiber with highland bamboo- glass fiber polyester hybrid composite reduces the composite material's water uptake. A reduction was found, however, the density was increased. It is challenging to employ row bamboo for the construction of hydrokinetic turbine blades as water ingress of the composite must be avoided even in the presence of erosion caused by cavitation and impact with foreign bodies in the water. Alkali - treated highland bamboo/glass fiber polyester hy brid composite is the most appropriate of the materials studied for the manufacture of a hydrokinetic turbine blade that is exposed to different structural loading while submerged in water.