Truc T. Ngo

Improving the Compostability of Natural Fiber-Reinforced Thermoset Composites with a Tertiary Oil Phase

Although fiberglass-reinforced composites play important roles in many industrial applications, the non-biodegradability of the fibers poses some environmental concerns. In this study, bamboo, cotton and hemp are used as natural reinforcing fibers for polyester and epoxy composites. A tertiary oil phase is also added to the matrix and its effect on material biodegradability is characterized. Results show that material biodegradability is increased up to 100% under controlled composting conditions with oil addition. Polyester biodegrades more effectively than epoxy under both macroscopic and microscopic mechanisms. Mechanical strengths of the polyester composites are also found to correlate strongly with material biodegradability.

Improving Mechanical Properties of Thermoset Biocomposites by Fiber Coating or Organic Oil Addition

Two different thermoset biocomposite systems are experimented in this study with the hope to improve their mechanical properties. Fiberglass and hemp, in form of fabrics, are used to reinforce the thermoset polymer matrix, which includes a traditional epoxy resin and a linseed oil-based bioresin (UVL). The fiber/polymer matrix interface is modified using two different approaches: adding a plant-based oil (pine or linseed) to the polymer matrix or coating the fibers with 3-(aminopropyl)triethoxysilane (APTES) prior to integrating them into the polymer matrix. Epoxy resin is cured using an amine-based initiator, whereas UVL resin is cured under ultraviolet light. Results show that hemp fibers with APTES prime coat used in either epoxy or UVL matrix exhibit some potential improvements in the composite’s mechanical properties including tensile strength, modulus of elasticity, and ductility. It is also found that adding oil to the epoxy matrix reinforced with fiberglass mostly improves the material’s modulus of elasticity while maintaining its tensile strength and ductility. However, adding oil to the epoxy matrix reinforced with hemp doubles the material’s ductility while slightly reducing its tensile strength and modulus of elasticity.

Characterization of Compostability and Mechanical Properties for Linseed Oil Resin Composites Reinforced with Natural Fibers

This work characterizes biodegradation behavior and mechanical properties of fiber-reinforced composites made from renewable sources. A linseed oil-based thermoset is used as the polymer matrix. Bamboo, cotton, hemp and fiberglass are used as the reinforcing fibers. Although tensile properties of comparable material systems have been reported in literature, characterization of their compostability has not been studied. Our experimental results show that the natural fibers degrade well under controlled composting conditions, whereas the thermoset polymer matrix did not. Tensile properties of the material are improved significantly with fiberglass reinforcement, whereas the natural fiber reinforcement is able to enhance the materials ductility.

Determining the viscoelastic properties obtained by depth sensing microindentation of epoxy and polyester thermosets using a new phenomenological method

Epoxy and polyester thermosets are currently used as the polymer matrix material for many fiber-reinforced composite systems. The viscoelastic properties of these materials were investigated in this study by use of depth sensing microindentation. The microindentation tests performed had the load being applied at a rapid loading rate to a maximum load. This maximum load was held constant while the stylus continued to sink. It was then unloaded at a nominal rate. A new phenomenological model developed by Schwarzer in 2014 was used in this work to determine the viscoelastic properties. Two approaches or methods were used. The first method involved determining the three parameters by using hold time data combined with unloading data (this method is referred to in this work as ‘hold time method’). The second method used only the unloading data (this method is referred to in this work as ‘unloading method’). It was shown that the properties determined by the two methods are not the same but are dependent upon the strain rate behavior during the indentation test. Low load scratch tests were also performed. It was seen that as the sliding speed increased the depth of penetration decreased resulting in the coefficient of friction also decreasing. An understanding of the viscoelastic properties at the surface and how they affect friction are important in studying wear of these materials.

Green Surfboards: Investigation of Product Biodegradability at End of Life

As the world becomes more environmentally conscious, companies find ways to make products and manufacturing processes greener. This work examines an innovative surfboard product that uses bio-based fiber-reinforced polymers to address product disposal issues and to lower the toxicity associated with some of its components and manufacturing processes. The goal of this work is to characterize the biodegradability of the “green” surfboards at end of life, focusing on the fiber-reinforced composite laminate covering the surfboard and the core of the board. Different laminate types, with various combinations of resins (polyester, epoxy and a bio-resin) and reinforcing fibers (fiberglass, organic hemp and organic cotton), were tested. Polyurethane core was compared with the green alternative balsa wood core. Degree and rate of biodegradability of materials were evaluated by measuring weight change and material hardness over 56 days under controlled composting conditions. The results suggest that the resin component in the composite laminate is the key factor that controls the rate of biodegradation of the material. In addition, different resins exhibit different degradation mechanisms, depending on the chemical and biological nature of the materials.

Humanitarian engineering opportunities and challenges in rural dominican republic: A case study of El Cercado

In developing countries, there are many humanitarian engineering opportunities ranging from healthcare to agriculture, water, sanitation, and energy. The governments in some developing countries, including the Dominican Republic, often focus on industrial and economic development in larger cities. Consequently, remote villages become more isolated, relying on limited local resources and traditional practices to sustain daily living. The situation, however, creates opportunities for non-profit groups to support the ongoing work of organized community initiatives and begin new regional developments. This paper reports a partnership model and project implementation strategy employed in a case study for El Cercado, a rural town located in southwestern Dominican Republic. Over two years, the engineers from the University of San Diego had partnered with El Cercado community to establish more fuel-efficient and safe cooking methods, improve drinking water sources, provide an affordable solution to water heating for sanitary purposes, and invent ways to minimize fuel costs. The next challenge is to transfer these technologies to local Dominicans, and assist them in developing business models for long-term sustainability. Advantages and challenges to local development initiatives such as cultural barriers, social acceptance, community leadership, and economic certainty are also presented.

Comparing the attitudes towards engineering of honors students and engineering students at a liberal arts university

In Fall 2012, 53 honors students and 53 engineering students (including seven students in both honors and engineering) completed a survey designed to examine their attitudes towards engineering and their ability to succeed in engineering. Preliminary analysis of five factors shows that the attitudes of engineers and honors students were similar in many respects. The main areas of difference were that honors liberal arts students had lower confidence in their ability to succeed in science and math and all non-engineers showed lower aptitude for engineering. Non-engineering women showed slightly less affinity for solving open-ended problems. All students expressed similar attitudes about the creativity of engineers and their contributions to solving societys problems.