Microwave pyrolysis biochar characterization and modeling of char reinforced GFRP biocomposites

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University of New Brunswick
This research thesis focuses on the manufacturing and characterization of biochar synthesized from microwave pyrolysis, as well as the manufacturing, testing, and modelling of a novel three-part biocomposites through the addition of biochar as a reinforcing filler to the common glass-fiber reinforced polymer (GFRP) composite. Biochar was produced from both softwood and hemp feedstocks utilizing a large batch of one kilogram of biomass mixed with 10 wt.% of microwave absorber, pyrolyzed at a constant residence time of 1 hour. The microwave power levels of 2100, 2400, and 2700 Watts were selected after several preliminary trials. Pyrolysis heating rates for large batch of biomass loading was found ranging from 25-50 oC/min. A number of characterization techniques were employed for the biochars including physiosorption analysis, proximate/ultimate analysis, FT-IR spectroscopy, and nanoindentation. Overall characteristics were improved through increasing microwave powers during pyrolysis. Biocomposites were produced in-house through a pultrusion process, and varying the biochar matrix volume percentage by 5, 10, and 20%. Through mechanical testing, the addition of biochar was found to increase the flexural yield strength and modulus of the biocomposites to a maximum of 34 and 6.5% respectively at 20% hemp biochar loading. Tensile testing revealed that the addition of biochar had some influence on tensile properties of the biocomposites, with maximum tensile strength and modulus increases being 12.5 and 2.6% respectively. Rule of mixtures and homogenization micromechanical models were evaluated against the experimental results to determine their validity for these novel three-part biocomposites, with the largest percent difference being 13%. A finite element model was created and analyzed through Abaqus FEA software for homogenization modeling.