Early Experiments

We made our own testing apparatus to investigate the tensile and flexural strengths of flax, hemp, onion skin, and pomelo skin reinforced composites and compared their properties with that of CA without reinforcement. By comparing Young's and tensile moduli and sample distortion, we found that pomelo skin composite has the least tensile strength, followed by the control, flax, and hemp (the onion sample was too heterogeneous to test). By measuring thickness deformation and angle of crack, the flexural tests showed that pomelo has the least flexural strength, followed by CA, hemp, and flax.

However, we were sceptical of our results as bubbles formed by the rapidly-evaporating acetone that was present throughout the samples may have distorted the results. Also, the thickness to length ratio we used to account for the thickness differences may have been fallacious if the thickness to strength relationship is non-linear. We decided to redo our experiment with more homogeneous and controlled samples. We removed onion and pomelo reinforcements due to their poor performance and added human hair due to its strength and availability. We decided to do the conductivity test to determine whether our plastic is suitable for use in electronic devices.

Tensile Strength

We set up our apparatus as shown below:
Two clamps are used to hold the sample in place. A bucket hangs from the lower clamp. Weights are placed in the bottom bucket, in increments of 500g. After each addition of weight, the thickness of the sample is measured in three locations using a micrometer. Weights are added until the sample fracture and breaks.

Flexural Strength

For the flexural strength test, we cut a sharp point on the sample so that we were able to trace the track the sample made as it broke. This allowed us to find the angle of initial fracture as well the angle of ultimate break.