Thesis Defence: Replacing Rigid GFRP with Flexible, Durable, and Recyclable Alternatives for Aquatic Applications: A Multicriteria Design Approach

Haoyang Liu, supervised by Dr. Abbas S. Milani, will defend their thesis titled “Replacing Rigid GFRP with Flexible, Durable, and Recyclable Alternatives for Aquatic Applications: A Multicriteria Design Approach” in partial fulfillment of the requirements for the degree of Master of Applied Science in Mechanical Engineering.

An abstract for Haoyang Liu’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Please email abbas.milani@ubc.ca to receive the Zoom link for this defence.

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ABSTRACT

For structural components used in leisure industries, such as those in aquaparks, high load-bearing capacity along with lightweight materials are of primary interest. For this purpose, rigid (cured) fibre reinforced polymer (FRP) composites are currently used widely. However, they often result in large and stiff moulded parts, which lead to logistic challenges as well as added cost associated with transportation of the parts from the factory to the installation site and handling. Conventional FRP materials are also known to be difficult to recycle, raising concerns over environmental sustainability. One proposed solution may be to replace such legacy materials with flexible, durable, and recyclable polymer alternatives, while redesigning the support structures so that the overall integrity and load-bearing capacity of the components remain unchanged. The high flexibility of the alternative materials can enable them to be easily rolled or folded (i.e., reduce occupied space) during transportation. Towards the above application motivation, this thesis is a preliminary investigation towards replacing glass fibre reinforced polymer (GFRP) composites used in aquatic play structures, such as water slides, with flexible, durable, and recyclable alternatives. Three thermoplastic elastomer (TPE) materials, including two thermoplastic polyurethanes (TPU) and one thermoplastic vulcanizate (TPV), were chosen as candidate materials to be studied. The physical (density, hardness, surface roughness) and mechanical properties (tensile, flexure, hysteretic, abrasion, friction, puncture, impact) of the legacy (base) and new candidate materials were characterized through a series of coupon-level experiments and imaging. Material samples were also subjected to weathering exposures, including water and chlorinated water immersion, accelerated hygrothermal aging, and accelerated weathering in xenon lamp chamber. GFRP exhibited superior tensile strength and modulus, while the TPE candidates showed much higher flexibility and strain at break. TPU showed better abrasion and puncture resistance than the TPV candidate, as well as a lower coefficient of friction, but higher water absorption. Yellowing could be observed for TPU after weathering in xenon lamp chamber. No statistically significant changes in the tensile properties could be concluded for all tested materials upon weathering. Next, building on the above characterization test data, a multicriteria decision making method, namely PROMETHEE II, was implemented to evaluate and rank the legacy and candidate materials based on typical design criteria including cost, mechanical properties, weathering performance, and recyclability. Texin 285A (TPU) was ranked as the top choice. Design ideas to incorporate the flexible material into water slide flumes, including a honeycomb sandwich structure design and a diaphragm design, were also explored.