Flexural Strength

The composites have very similar initial fracture properties: all of the 25% and 45% reinforcement composites break at the first bend; the control can generally withstand up to four bends before fracturing. This is expected since the higher amount of fibre reinforcements, the lower amount of matrix, causing the stress to be more localized. CA breaks almost right away after its first crack, but the more reinforcement, the more bends a sample can withstand, due to a greater number of fibres bridging the stress away at the fracture point. For the 5% and 25% composites, the hair composites can withstand the most bends, followed by hemp, and flax. However, the 45% composites are very similar in performance.

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Graph F.1 shows that the more reinforcement, the more bends a sample can withstand, likely due to a higher probability of fibres present to bridge the stress away from the fracture point. However, this dependence on probability also makes composite strength vary from a certain spot to another. CA breaks almost right away after initial crack. For 5% and 25% composites, the hair composites can withstand the most bends, followed by hemp, and flax. The 45% composites are very similar in performance.

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The CA maximum bending stress was about 7 times greater than that of the composites. Within the composites, hair can withstand the highest stress; bending stress decreases as % reinforcement increases for all composites.