Available at: http://digitalcommons.calpoly.edu/theses/1362
Date of Award
MS in Aerospace Engineering
Over the last three decades, the aerospace industry has gradually shifted from metals to composites in many different applications due to the lightweight properties of composite materials. Some benefits of composites include higher strength-to-weight ratio and corrosion resistance. At this point in time, the composite industry researchers are focusing on renewable and sustainable materials (bio-composites). By understanding the structural capabilities of bio-composites that have been used for centuries, new developments of sustainable materials will spark more interest throughout the industry. Bio-composites include fibers such as hemp, bamboo, flax, etc. The high demand for bio-composites in composite structures can also reduce raw material costs.
This study investigated, through experimental and numerical analysis, the mechanical behavior of sandwich panels under edgewise compressive loading. The first task of the study was to use four different facesheet materials and the same Nomex honeycomb core. The number of facesheet layers consecutively increased from one layer to four layers on each side of the core for each material. The facesheet materials used were Hexply AGP280-5H Carbon Fiber Pre-Preg, B601 Plain Weave Hemp, D118DKBR Split Herringbone Weave Hemp, and NB308T 7725 Texalium Fiberglass Pre-Preg. The sandwich panels were cured using a composite heat press and followed the recommended cure cycle for the material’s resin matrix. The variation of the facesheet materials while keeping the core consistent showed how the edgewise strength and displacement of the composite sandwiches were affected under compressive loading. The second task of the study was to try and create a multifunctional hybrid composite sandwich with two different facesheet materials; using one hemp material and one pre-preg material. The goal of this task was to try and minimize the damage occured upon failure. Being that the pre-preg materials are more brittle than the hemp material, the hybrid composite sandwiches can potentially create a superior composite structure. The sequence of stacking of the facesheet materials was manipulated to study how changing the outer and inner layers affected the results. All the specimen were loaded at a rate of 0.05 in/min in a steel jig specifically made per ASTM C364 standard using an Instron 8801 to determine the mechanical behavior. These experimental results combined with results from theoretical and finite element analysis using Matlab and Abaqus, respectively, were used to compare composite sandwich designs under compressive loadings. Failure mode comparison between the individual material composites and the hybrid composites were also discussed.