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Previously reported vertical UL-94 testing results showed that carbon nanofiber z-threaded carbon fiber-reinforced polymer (ZT-CFRP) laminates have significantly improved flame resistance capabilities compared to traditional carbon fiber-reinforced (CFRP) laminates. Shorter flame self-extinguishing times and no flame propagation were reported. These characteristics provided evidence that ZT-CFRP’s unique microstructure, combined with its inherent strengthened mechanical, thermal, and electrical properties, has the potential to have more favorable high-temperature applications than traditional CFRP. This study examined the interlaminar shear strength (ILSS) enhancement of ZT-CFRP laminates, in comparison to traditional CFRP, when exposed to gradually increased temperatures. This was accomplished through the use of a furnace and an in-house constructed three-point bending apparatus capable of supplying static loading to determine the temperature at which failure occurred. The apparatus was loaded with a specimen and then placed inside the furnace where the temperature was allowed to increase based upon a consistent heating schedule. It was observed that ZT-CFRP samples had an approximately 30 ˚C improvement in temperature handling capabilities while exposed to an interlaminar shear load when compared to CFRP samples. Microscopic image analysis was also performed to observe how CNF z-threads contributed to the improved performance observed for ZT-CFRP at extreme elevated temperatures.
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Flammability characterization of carbon nanofibers and nanotubes z-threaded CFRP laminates
Carbon fiber reinforced polymer (CFRP) composites have been increasingly used in many vehicles such as airplanes, automobiles, and ships due to the advantages of high-strength, high-modulus, lightweight, and corrosion resistance. CFRP structures enhance the vehicle's performance, energy-efficiency, comfort, and safety. However, a common safety concern is how the CFRP materials perform when the vehicle is in fire and if there are enough time to safely evacuate the passengers. The elevated temperature can soften and decompose the polymer matrix, delaminate the CFRP laminate, and burn the CFRP through the contact with oxygen. As a result, the thermal and flammability response of CFRP is important for considering CFRP for vehicle applications; and some specialty high-temperature or flame/smoke/toxicity-proven resins have been investigated for CFRP parts manufacturing due to the needs. In this paper, a novel flame resistant hypothesis of utilizing the unique nano/micro- interlocked fiber reinforcing structure of the long-range carbon nanofiber z-threaded CFRP (ZT-CFRP) composite laminates for improving the flammability performance will be investigated. The carbon nanofibers (CNT) and carbon nanotubes (CNT), which have excellent thermal and mechanical properties, will be dispersed in an epoxy resin and will zig-zag thread through a carbon fiber fabric using an electrical/flow assisted impregnation process to create the unidirectional ZT-CFRP prepregs, respectively, which will be further processed into ZT-CFRP composite laminates. The UL-94 flammability test will be employed to characterize the ZT-CFRP laminates' flammability performance against the control baseline data of the regular CFRP, all without using any flame retardant chemicals. An impressive self-extinguishing flammability characteristic of the CNF based ZT-CFRP samples has been distinctly identified from all the samples. The UL-94 testing results and the effectiveness of using the long-range nanofiber z-threading strategy for enabling the novel nano/microstructure-induced flame resistant and self-extinguishing characteristics will be discussed.
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- Award ID(s):
- 2044513
- PAR ID:
- 10386717
- Date Published:
- Journal Name:
- CAMX Conference Proceedings. Anaheim, CA, October 17-20, 2022.
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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