skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Effects of sample shape and adhesive type on rheology of unidirectional carbon fiber prepregs
The viscoelastic properties of carbon fiber reinforced thermoset composites are of utmost importance during processing such materials using composite forming. The quality of the manufactured parts is largely dependent on intelligent process parameter selection based on the viscoelastic and flow properties of the polymer resin. Viscoelastic properties such as the complex viscosity (η*), storage modulus (G'), loss modulus (G''), and loss tangent (tanδ) are used to determine the critical transition events (such as gelation) during curing. An understanding of the changes in viscoelastic properties as a function of processing temperature and degree of cure provides insight to establish a suitable processing range for compression forming of prepreg systems. However, tracking viscoelastic properties as a function of cure during the forming process is a challenging task. In this current work, we have investigated the effect of sample size and adhesive type on the rheological properties of a commercially available carbon fiber prepreg material. Specifically, determining the linear viscoelastic region (LVE) as a function of sample configuration and different adhesive chemistries were explored. The results suggest that the square-shaped sample geometries coupled with cyanoacrylate based adhesive are optimum for conducting rheological characterization on the carbon fiber prepreg system.  more » « less
Award ID(s):
1854185
PAR ID:
10573787
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Annual Technical Conference - ANTEC, Conference Proceedings
Date Published:
Format(s):
Medium: X
Location:
Charlotte, NC
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; (, Journal of Thermoplastic Composite Materials)
    null (Ed.)
    Carbon fiber (CF)-reinforced thermoplastic composites have been widely used in different structural applications due to their superior thermal and mechanical properties. The big area additive manufacturing (BAAM) system, developed at Oak Ridge National Laboratory’s Manufacturing Demonstration Facility, has been used to manufacture several composite components, demonstration vehicles, molds, and dies. These components have been designed and fabricated using various CF-reinforced thermoplastics. In this study, the dynamic rheological and mechanical properties of a material commonly used in additive manufacturing, 20 wt% CF-acrylonitrile butadiene styrene (ABS), as well as three CF-reinforced high-temperature polymers, 25 wt% CF-polyphenylsulfone (PPSU), 35 wt% CF-polyethersulfone (PES), and 40 wt% CF-polyphenylene sulfide (PPS), used to print molds were investigated. The viscoelastic properties, namely storage modulus, loss modulus, tan delta, and complex viscosity, of these composites were studied, and the rheological behavior was related to the BAAM extrusion and bead formation process. The results showed 20 wt% CF-ABS and 40 wt% CF-PPS to display a more dominant elastic component at all frequencies tested while 25 wt% CF-PPSU and 35 wt% CF-PES have a more dominant viscous component. This viscoelastic behavior is then used to inform the deposition and bead formation process during extrusion on the BAAM system. 
    more » « less
  2. (, Society of Plastics Engineers (SPE®) International www.4spe.org)
    Carbon fiber reinforced polymer (CFRP) is one of promising lightweight materials for advanced air mobility (and electrical vehicles) due to the high strength, low density, and corrosion resistance. On the other hand, CFRP is more expensive than many lightweight alloys, difficult to join, less fire-resistant, lower conductivities in thermal and electrical energy, more sensitive in processing defects, and more difficult to inspect its structural damages. To improve the multifunctionality desired by advanced air mobility, CFRP could be modified with nanoparticles. Nanofiber z-threaded CFRP (ZT-CFRP) technology utilizes millions of long carbon nanofibers to z-directionally thread through all carbon fibers in per square-centimeters of ZT-CFRP prepreg. The ZT-CFRP enhanced the mechanical properties, thermal conductivity, and electrical conductivity. The unique 3D-multicscaled fiber-reinforced microstructure also provide additional performance such as enhanced resistance against the property degradation caused by void, enhanced flame-retardance, improved adhesive-joint (i.e., bond line) strength, and enhanced thermal infrared damage/defect evaluation resolutions. This paper will overview the ZT-CFRP performances along with the state of ZT-CFRP prepreg process development including the scaled up roll-to-roll hot-melt manufacturing process of the ZT-CFRP prepreg. Its potentially useful multifunctional attributes for advanced air mobility will also be discussed in this paper. 
    more » « less
  3. ; ; ; ; (, Composites Part B: Engineering)
    In automated layup manufacturing processes of fiber-reinforced polymer composites, the quality of the manufactured part is strongly dependent on frictional behavior. Improper control of frictional forces can lead to defect formation. Frictional sliding rheometry tests provide an innovative methodology to accurately characterize the tool-ply friction of unidirectional (UD) prepreg employing unique annular plate geometries. The effect of processing parameters (temperature, velocity, and normal force) on the frictional response of a carbon fiber prepreg was studied. Moreover, utilizing custom designed plate geometries coupled with optically transparent fixtures allowed for in-situ quantification of the prepreg-rigid surface contact area along with simultaneous characterization of the process parameter-dependent frictional mechanisms. Our findings highlight the reduction in frictional forces with increasing temperature, attributed to the increased resin flowability, while increases in sliding rates resulted in a pronounced increase in the frictional forces. The effect of applied load on the frictional characteristics was more complicated due to contributions from both the adhesive and normal forces. Finally, the results were interpreted in light of the contact area measurements performed at different temperatures, normal force, and sliding rate. 
    more » « less
  4. ; ; ; (, SAMPE 2022 Conference Proceedings, Charlotte, NA, May 23-26, 2022)
    Moisture is a known issue for carbon fiber reinforced polymer (CFRP) manufacturing. During the process, in which a CFRP prepreg is carefully thawed, cut, stacked, and cured into a laminate, any bad moisture control can cause voids, affect the curing, and degrade the laminate. Recent studies of carbon nanofiber z-threaded CFRP (i.e., ZT-CFRP) prepreg and its laminates showed significant multifunctional improvements in the mechanical strengths, toughness, thermal conductivity, and electrical conductivity. The carbon nanofibers zig-zag thread among the carbon fibers in the through-thickness direction (i.e., z-direction) and mechanically interlock the fiber system together to form an effective 3D-fiber-network reinforced laminate. This paper presents a preliminary experimental study on the ZT-CFRP prepreg when facing the moisture exposure during the prepreg handling and lamination process. Both the ZT-CFRP and traditional CFRP prepregs, subjected to different humidity conditions, will be cut, and cured into laminate samples. The samples will be tested for their interlaminar shear strengths (ILSS) and hardness. Microscope pictures of the samples' fracture patterns will be compared for explaining the combined impact of the moistures and the carbon nanofiber z-threading strategy on the laminates' interlaminar shear strength and curing state. 
    more » « less
  5. ; ; (, Proceedings of the Composites and Advanced Materials Expo (CAMX))
    Previous studies have shown how discontinuous resin formats can increase the robustness of Vacuum Bag Only (VBO) prepregs. Current formats of this discontinuous resin format, dubbed USCPreg, all rely on a discontinuous film being applied on a fiber bed using only pressure. However, efforts are currently being undertaken to apply the discontinuous resin to the fiber bed directly, without a separate filming step. These methods should allow broader and more diverse characteristics of the prepreg, and allow a reduction in bulk factor, customization of the resin distribution, and potentially enable the production of prepreg “on demand.” To understand how applying discontinuous resin to a dry fiber bed at temperatures suitable for resin deposition may affect the final distribution, small-scale experiments were conducted. A fluid with controlled viscosity, matching the viscosity of epoxy resin during hotmelt processing, was used to minimize variability. The experiments consisted of a sessile droplet of facsimile fluid being deposited on the surface of a single ply of reinforcement. The spread of the fluid was then recorded, using a goniometer as well as a standard camera. Post-processing of these recordings was performed to obtain the spreading of the fluid in three directions: in the plane directions and the out-of-plane direction. The fluid was constant, a 30Pa.s rheological standard, but the reinforcement was varied to determine how the fluid interacted with different reinforcements. Macro-scale changes, such as fabric weave and fabric areal weight, and micro-scale parameters, such as tow width and fiber size, were varied to observe their effects on fluid distribution. The experiments yielded maximum in-plane spread distance, time for the resin to fully impregnate into the fibers, and aspect ratio of spreading, particularly for non-symmetric weaves. The results can be used to guide how the resin is deposited on different reinforcements, in order to achieve a resin distribution that will consistently yield high-quality parts. In addition, it is possible these observations can be applied to resin flow in standard continuous film prepreg, such as predicting the final degree of impregnation. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email