Carbon fiber reinforced polymer (CFRP) composites have been increasingly used to replace metal parts in many industries such as aerospace, marine, automotive, and sporting goods. The CFRP parts compared with their metallic counter parts have the advantages of lightweight, significantly higher tensile strength, stiffer, and corrosion resistant. On the other hand, compared with many metal parts, the CFRP parts have many well-known disadvantages including the lower toughness, lower through-thickness tensile and shear strengths, lower thermal conductivity, lower electrical conductivity, and lower operating temperature. These disadvantages have made the conversion from metal parts into CFRP parts challenging and costly to design, manufacture, and maintain.
The use of nanoparticles in polymer has been studied in the recent two decades. Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been dispersed in various thermoset and thermoplastic polymers and improved the mechanical, electrical, and thermal properties; however, the properties were not comparable to CFRP. Later, researchers tried to infuse CNTs or CNFs into either carbon fiber preforms [1] or glass fiber preforms [2] for improving the mechanical properties. But the results were marginal and with great uncertainty due to the challenges of nanoparticle dispersion, filtering, and alignment while being infused through the fiber preform. The glass fiber preform experiments ended with relatively more consistent improvement than the carbon fiber preform experiments since that the glass fiber preform has significantly larger pores than the carbon fiber preform' s. The small pore size presented a great challenge for infusing millions of unaligned long CNTs or CNFs through the carbon fiber preform without being filtered.
To infuse long CNFs or CNTs through the carbon fiber preform and achieve reliable improvements, especially for 55% or higher carbon fiber volume fraction with increasingly tighter pores, an innovative plan for the processing and nano-reinforcing strategy is necessary. The z-threading strategy [3, 4, 5] has been reported to have consistent experimental successes in achieving the statistically meaningful improvement in multifunctional properties. The manufacturing steps of the CNF z-threaded CFRP (ZT-CFRP) are: (1) disperse the CNFs in a resin, (2) use a strong electrical field to align the CNFs in either the B-stage epoxy film or a CNF/resin impregnated sponge layer, whereas the CNFs are aligned in the through-thickness direction of the film or sponge layer. (3) place the resin film or sponge layer on a preheated dry carbon fiber fabric and press the resin film into the hot carbon fabric and allow the resin flow to carry the well-aligned CNFs to thread through the pores in the carbon fabric. (4) cool down the resin saturated and CNF z-threaded carbon fiber fabric to obtain the ZT-CFRP prepreg. (5) use the ZT-CFRP prepreg to make the ZT-CFRP laminate. Compared with the traditional CFRP, the ZT-CFRP laminates were reported of having improvement in the Mode-I delamination toughness, interlaminar shear strength, longitudinal compressive strength, through-thickness electrical conductivity, through-thickness thermal conductivity, and can reach the carbon fiber volume fraction of 55-80%. It is an effective approach to achieve a multifunctional CFRP for potentially expanding CFRP's applications.
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IMPROVE THE THROUGH-THICKNESS ELECTRICAL CONDUCTIVITY OF CFRP LAMINATE USING FLOW-ALIGNED CARBON NANOFIBER Z-THREADS
Traditional Carbon Fiber Reinforced Plastics (CFRPs), carry high in-plane strength and electrical conductivity but exhibit intrinsic weaknesses in strength, toughness and conductivity in the through-thickness direction (i.e. z-direction). This paper presents a novel approach to align and thread Carbon Nanofibers (CNFs) through the porous medium (Carbon fiber fabric) using an interesting radial-flow alignment method and manufacture a novel CNFs z-threaded CFRP prepreg. This new radial-flow alignment approach is unique and has been found highly effective to z-thread the array of carbon fibers (diameter ~ 7 microns) with numerous long CNFs (length ~ 50-200 microns) under a Scanning Electronic Microscope (SEM) analysis. Experimental tests performed on a cured laminate sample prepared by this novel technique with 1 wt% aligned CNF concentration showed a significant improvement on the z-directional electrical conductivity for direct current (DC). The 1 wt% CNFs z-threaded CFRP was found about 100 times as conductive as the control CFRP; whereas the unaligned 1 wt% CNFs modified CFRP was only about 16 times as conductive as the control sample.
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- Award ID(s):
- 1748369
- NSF-PAR ID:
- 10075362
- Date Published:
- Journal Name:
- International SAMPE Symposium and Exhibition
- ISSN:
- 0891-0138
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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