Yeong-Min Baek

Investigation of Interfacial and Mechanical Properties of Various Thermally-Recycled Carbon Fibers/Recycled PET Composites

The mechanical and interfacial properties were evaluated for carbon fiber reinforced composites (CFRC) manufactured using thermally recycled waste carbon fiber and recycled polyethylene terephthalate (PET). The mechanical properties of the recycled fiber were determined and compared to those of neat fibers using the single-fiber tensile test. The surfaces of the recycled and neat carbon fiber were examined and compared using FE-SEM and dynamic contact angle measurements. A goal of the study was to determine the applicability of industrial use of recycled CF and/or recycled PET in CFRC. Mechanical properties were measured using short beam and tensile tests. These properties were observed to be correlated with crystallinity. The interfacial properties between the recycled carbon fibers and recycled PET were evaluated using the microdroplet test. At low temperature residual resin remained on the recycled CFs surface resulting relatively the low interfacial properties. At excessively high temperatures, oxidation occurred, on the CFs surface, which also resulting in relatively poor low mechanical properties. The optimal treatment condition was 500 °C, where the surface was relatively clean and the reduction in mechanical properties was minimized.

Evaluation of Interfacial and Mechanical Properties of Glass Fiber/Poly-Dicyclopentadiene Composites with Different Post Curing at Ambient and Low Temperatures

Recently new poly-dicyclopentadiene (p-DCPD) has increasing been used for composites in military, aerospace, and transportation applications due to its favorable impact properties. In this work, the cross-linking density of p-DCPD with different post curing conditions was indirectly measured by thermal analysis using differential scanning calorimetry (DSC), weight variation accompanying swelling and density. The effects of the post curing conditions on mechanical properties of p-DCPD and glass fiber (GF)/p-DCPD were determined via tensile, Izod impact, and flexural tests at ambient and low temperatures (-20 °C). Interfacial properties were evaluated by fragmentation and cyclic loading tests. The work of adhesion was determined via Static contact angle using four solvents measurements, to provide the information on the differences in the interfacial properties between GF and p-DCPD. The change of cross-linking density by post curing of p-DCPD affected the mechanical and interfacial properties of GF/p-DCPD composites.