ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2024 25 specific strength and specific modulus (Fig. 2). The highest performance laminate exhibited a specific modulus of 256 GPa/(g·cm-3) and a specific strength of 1.71 GPa/(g·cm-3). However, these laminates still fell short of their theoretical maximum mechanical properties due to suboptimal load transfer within yarns as evidenced by their low resin content and brittle tensile failure behavior. RADICAL RESULTS Due to lack of accessibility to the densely packed CNT yarns by chemical treatment, US-COMP next investigated the use of high energy radiation to fully enhance the interfacial bonding properties between CNT yarn and resin[6]. To better understand the effects of irradiation of these CNT yarns on overall composite performance, the yarns were exposed to a range of radiation doses, from 50 to 1200 kGy, before laminate fabrication with one of the previously identified compatible resins. Results of testing on the CNT yarns revealed only slight increases in specific strength and specific modulus, with maxima of both occurring at 200 kGy, matching the expected trend for modulus vs. radiation dose shown by computational tools (Fig. 3). However, it was the laminate containing CNT yarns exposed to 700 kGy that showed the greatest increases in both specific strength a dramatic increase in specific modulus between the CNT yarns and the CNT yarn laminates with a maximum 2.76× increase, a phenomenon not observed in traditional CF composites. Combined with high specific strengths, these CNT laminates unlock a new performance region in the Ashby chart for Fig. 1 — Microstructure of CNT yarn laminate: (a) photograph of CNT yarn laminate; (b) SEM cross-section of laminate showing densely-packed CNT yarns; and (c) higher-resolution SEM image of laminate cross-section with interfaces between individual CNT yarns clearly visible[5]. Fig. 2 — Comparison of high specific tensile modulus and strength unidirectional CNT yarn laminates to state-ofthe-art high-modulus and high-strength CFRPs[5]. (a) (c) (b)
RkJQdWJsaXNoZXIy MTYyMzk3NQ==