Author(s): R. Panford , O. Akuffo , E. Klutse, T. Charles-Debrah Charles-Debrah
Keywords: material selection; strain sensor; furniture; ultimate tensile strength; stool
In this project, experiments were performed to explore cost-effective materials in the designing of the seating surface of a stool. Conventional materials were considered, such as paper, naturally occurring substances, and plastics for fabrication to minimize cost. According to Garside, the global production of paper stood at 411 million metric tons, as of 2016, rating paper as one of the most used materials in the world . Paper is defined as a material manufactured in thin sheets from the pulp of wood or other fibrous substances, which can be used for writing, drawing, or printing on and as well as wrapping material . Paper was selected because it is easy to come by due to its mass production. The thickness of a paper can be measured with a pair of vernier calipers. The strength and durability of paper are based on the type of material used to make it and the length of it, respectively. For this experiment, A4 sheets were selected for use, since they are ubiquitous. Next, leaves from the Brahma Edulis tree were chosen for this project because they are ubiquitous .The Brahma tree is like a palm tree with its leaves in the shape of a fan. The tree grows to a height between 4.5 -13 meters tall. This plant was the best choice at our disposal because of its proven strength and durability, which were some of the features in our design. Finally, plastics were chosen to curb the problem of plastic waste pollution. Plastic straws cannot be easily recycled, and hence they are littered everywhere and typically end up in the ocean. According to Ocean Conservancy's Tides system, straws made up a considerable portion of the trash in the sea, in early 2018. Five hundred million straws are used daily in the USA. This number is enough to circle round the earth 2.5 times . Based on this problem, this experiment considered it as one of the materials, with the aim of recycling plastic straws to reduce plastic waste pollution.
This project delves into the experimental and statistical analysis of material selection factors such as availability, cost efficiency, and durability, tensile strength, and sagginess of materials that could be potentially used to build the seating area of a foldable wooden stool. In the course of the experimental process, paper, plastic, and leaves were used as the experimental groups for the analysis. A further test was carried out to test if weaving patterns of the materials affected tensile strength. The mechanical properties of the experimental groups were statistically analyzed to decide on the material’s usability. Conclusively, plastic straws had the highest tensile strength and least sag per unit mass, making it the most suitable material amongst the three to withstand the higher load placed on the seating area. In attempts to reduce the sagginess of the plastic straw, two weaving patterns, rustic plait, and, three-strand braid, of equal length underwent a repeated sagginess test. The rustic plait weaving pattern resulted in the least sag per 700g loaded on it. With these results the seating area of the stool was fabricated from rustic-plaited plastic straws.
There was statistical significance obtained in the ultimate tensile stress tests as well as the sagginess tests, indicating the mean ultimate tensile stress’ of the three materials, as well as the mean sagginess of the three materials, are not equal, rejecting their null hypotheses. Thus, enabling the selection of a suitable material for the designing of the seating area of the stool. A material with the highest tensile strength, as well as the least sag per unit mass placed on it, is the preferred material to be used for the seating area of the stool to be able to withstand a higher load placed on the stool than the others. With these preferences, plastic straws concluded in being the most suitable material to be used for the seating area of the stool. Still with an aim to achieve the least sag per unit mass placed on the stool, the rustic plait weaving pattern of the plastic straw was used, as from tests conducted had sagged the least per 700g placed on it as compared to the linear three-strand braid. Based on this material and weaving pattern selection the foldable wooden stool was built as shown in Fig. 4 and Fig. 5 with its seating area being plastic straws woven in rustic plait patterns. The durability of the seating area is the primary factor in the experiment; hence, the plastic deformation that the straw goes through is not convincing enough. Nevertheless, a potential solution for increasing the durability of the seating area is to bind the straw strips with an adhesive. The prototype above is still under iterative research and redesigning process, as things stand, Ahuod3n is suitable for the average child between the ages of 3-10 years old due to the low elastic limit of straw strips.