Processability and physical environmental protection methods of natural fiber thermoset composites

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School of Engineering | Master's thesis
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The purpose of this thesis is twofold. The first study is to evaluate the process ability of four different natural fibers on the basis of void volume content and fiber volume content. The purpose of the second study is to evaluate the effects of moisture in natural fiber reinforced composites and the potential of different coatings to protect the laminates. Because natural fibers absorb so much moisture it is important for the growth of the industry to understand both their reaction to this absorption and how to prevent it. The fiber with the best process ability will be selected for additional experiments which will include moisture absorption, tensile, and compression tests. For the moisture absorption tests four coatings will be compared to specimens without coating and for the tensile and compression specimens two coatings will be compared to specimens without coating. All laminates were created via infusion technique under as similar conditions as possible. Of the four natural fibers looked at in the first study, the Lyocell fiber obtained significantly better fiber volume (57.4 %) and void volume (2.4 %) than any of the three flax fibers. Lyocell was chosen to be used in the second study. In the second study, no one coating stood out above the others. However, there was a correlation between the thickness of the coatings and the time it took for the laminate to fully saturate. There was also a correlation between the percent moisture absorbed and the decrease in tensile and compression modulus and ultimate stress and strain. From the tensile tests, the drop in modulus was significant enough to show that it was the fibers being affected by the moisture. More research needs to be conducted on both the effects of moisture and on different coatings to better understand these issues.
Saarela, Olli
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Santamala, Harri
natural fibers, composites, moisture absorption, coatings
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