Research Question

In an anisotropic short fibre reinforced cellulose acetate composite material, how do different natural fibres -- hemp, flax, pomelo skin, onion skins, and human hair -- affect the tensile strength, flexural strength, and conductivity of the composite material? As well, what is the optimal amount of fibre reinforcement content by mass?

Variables

Dependent variables:

• Tensile strength: amount of force applied over time; length sample is distorted after breaking
• Flexural strength: # of times a sample bends before initial crack and before complete break; difference between bends before initial and complete break; maximum bending stress
• Conductivity: amount of current that passes through a circuit with the samples as resistors

Independent variables:

• Type of fibre: Flax, hemp, human hair
• Amount of fibre within sample (by mass): 5%, 25%, 45%

Controlled variables:

• Dimensions, mass, and amount of fibres in sample
• Uniform fibre length (0.4 and 0.6 cm); acetone volume per matrix mass
• Uniformity of testing environment (esp. temperature/moisture due to hygrothermal effect)

Method for controlling variables: To ensure greater precision, we conducted 6 trials for each amount of each type of fibre for the tensile strength test and 4 for the flexural strength test. Of these, two samples are cut from 2 random locations on each piece. The composite was poured as a liquid into Petri dishes of the same size to ensure samples for each trial will have the same dimensions and mass. We conducted the tests at the same time and location.