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.


  • NSF Public Access
  • Search Results
  • Experimental evaluation on the longitudinal compressive strength of carbon nanofibers z-threaded CFRP laminate manufactured by the magnetic compaction force assisted additive manufacturing method
Title: Experimental evaluation on the longitudinal compressive strength of carbon nanofibers z-threaded CFRP laminate manufactured by the magnetic compaction force assisted additive manufacturing method
The matrix sensitive weaknesses of Carbon Fiber Reinforced Polymer (CFRP) laminates are usually magnified by mainstream additive manufacturing (AM) methods due to the AM-process-induced voids and defects. In this paper, a novel Magnetic Compaction Force Assisted-Additive Manufacturing (MCFA-AM) method is used to print Carbon Nanofibers (CNF) Z-threaded CFRP (i.e., ZT-CFRP) composite laminates. The MCFA-AM method utilizes a magnetic force to simultaneously support, deposit, and compact Continuous Carbon Fiber Reinforced Polymer (C-CFRP) composites in free space and quickly solidifies the CFRP part without any mold; it effectively reduces the voids. Past research proved that the zig-zag threading pattern of the CNF z-threads reinforces the interlaminar and intralaminar regions in the ZT-CFRP laminates manufactured by the traditional Out of Autoclave-Vacuum Bag Only (OOA-VBO) method, and enhances the matrix sensitive mechanical, thermal, and electrical properties. In this study, the longitudinal compressive test (ASTM D695, i.e., SACMA SRM 1R-94) was performed on the MCFA-AM printed ZT-CFRP laminate. The results were compared with unaligned CNF-modified CFRP (UA-CFRP), control CFRP, and no-pressure CFRP samples’ data to investigate the impact of the CNF z-threads and MCFA-AM process on the CFRP’s performance. The 0.5-bar MCFA-AM printed ZT-CFRP showed comparable longitudinal compressive strength with the 1-bar OOA-VBO cured CFRP.  more » « less
Award ID(s):
2044513
PAR ID:
10482578
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
SAMPE
Date Published:
Journal Name:
CAMX 2023 Technical Proceedings
Subject(s) / Keyword(s):
Magnetic Compaction Force Assisted-Additive Manufacturing Carbon Nanofiber Z-threaded CFRP longitudinal compressive strength
Format(s):
Medium: X
Location:
Atlanta, GA
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; (, Materials)
    Carbas, Ricardo JC (Ed.)
    Low fiber-direction compressive strength is a well-recognized weakness of carbon fiber-reinforced polymer (CFRP) composites. When a CFRP is produced using 3D printing, the compressive strength is further degraded. To solve this issue, in this paper, a novel magnetic compaction force-assisted additive manufacturing (MCFA-AM) method is used to print CFRP laminates reinforced with carbon nanofiber (CNF) z-threads (i.e., ZT-CFRP). MCFA-AM utilizes a magnetic force to simultaneously levitate, deposit, and compact fast-curing CFRP prepregs in free space and quickly solidifies the CFRP laminate part without any mold nor supporting substrate plate; it effectively reduces the voids. The longitudinal compressive test was performed on five different sample types. ZT-CFRP/MCFA-AM samples were printed under two different magnetic compaction rolling pressures, i.e., 0.5 bar and 0.78 bar. Compared with the longitudinal compressive strength of a typical CFRP manufactured by the traditional out-of-autoclave–vacuum-bag-only (OOA-VBO) molding process at the steady-state pressure of 0.82 bar, the ZT-CFRP/MCFA-AM samples showed either comparable results (by −1.00% difference) or enhanced results (+7.42% improvement) by using 0.5 bar or 0.78 bar magnetic rolling pressures, respectively. 
    more » « less
  2. ; ; ; (, Applied Sciences)
    Manoj Gupta (Ed.)
    Three-dimensional (3D) printing with continuous carbon-fiber-reinforced polymer (C-CFRP) composites is under increasing development, as it offers more versatility than traditional molding processes, such as the out-of-autoclave-vacuum bag only (OOA-VBO) process. However, due to the layer-by-layer deposition of materials, voids can form between the layers and weaken some of the parts’ properties, such as the interlaminar shear strength (ILSS). In this paper, a novel mold-less magnetic compaction force-assisted additive manufacturing (MCFA-AM) method was used to print carbon nanofiber (CNF) z-threaded CFRP (ZT-CFRP) laminates with significantly improved ILSS and reduced void content compared to traditional C-CFRP laminates, which are printed using a no-pressure 3D-printing process (similar to the fused-deposition-modeling process). The radial flow alignment (RFA) and resin-blending techniques were utilized to manufacture a printing-compatible fast-curing ZT-CFRP prepreg tape to act as the feedstock for a MCFA-AM printhead, which was mounted on a robotic arm. In terms of the ILSS, the MCFA-AM method coupled with ZT-CFRP nanomaterial technology significantly outperformed the C-CFRP made with both the traditional no-pressure 3D-printing process and the OOA-VBO molding process. Furthermore, the mold-less MCFA-AM process more than doubled the production speed of the OOA-VBO molding process. This demonstrates that through the integration of new nanomaterials and 3D-printing techniques, a paradigm shift in C-CFRP manufacturing with significantly better performance, versatility, agility, efficiency, and lower cost is achievable. 
    more » « less
  3. ; ; ; (, SAMPE 2019 Proceedings, May 20-23, Charlotte, NC.)
    In this study, unidirectional carbon fiber prepregs that contain long carbon nanofiber (CNF) z threads as a through-thickness (z-directional) reinforcement were manufactured. The CNF z threads are long enough to thread through multiple carbon fiber (CF) arrays, which creates a multi-scale CNF/CF/resin-composite. The CNF z-threaded prepregs were manufactured using an electric-field aligned flow-transferring process. It was hypothesized that the CNF z-threads with the zig-zag threading pattern reinforces the interlaminar and intralaminar regions of the CFRP laminate thus improve the compressive strength by reducing the chance of carbon fiber buckling. Compressive testing was performed per modified version of ASTM D695 (i.e., SACMA SRM 1R 94) to evaluate the compressive strength of the CNF z-threaded CFRP (ZT-CFRP) laminates. The samples were manufactured using AS4 carbon fibers, EPON 862/Epikure-W resin and a 1wt% CNF content. ZT-CFRP testing results were compared with unaligned CNF-modified CFRP (UA-CFRP) and unmodified CFRP samples to investigate the impact of the CNF z-threads on the compressive strength. Results showed an increase of ~15% for the compressive strength of ZT CFRPs, whereas the UA-CFRPs experienced a decrease of ~8% when compared to unmodified CFRPs. It was concluded that CNF/carbon fiber interlocking stops and delays crack growth, and helps to stabilize carbon fibers from further buckling. 
    more » « less
  4. ; ; (, International Conference on Composite Materials (ICCM))
    Previous studies have shown that carbon nanofiber (CNF) z-threaded carbon fiber-reinforced polymer (ZT-CFRP) laminates exhibit improved mechanical performance in comparison to traditional carbon fiber-reinforced polymer (CFRP) laminates when exposed to extreme elevated temperatures. Z-threaded reinforcement is a technique for strengthening the through-thickness of a laminate by introducing perpendicularly aligned carbon nanomaterial to be threading into the continuous fiber array. Improved performance has already been observed in properties such as interlaminar shear strength (ILSS) without extreme heat exposure, but there has also been evidence that z-thread inclusion may mitigate strength loss due to thermal degradation of the matrix. This study examined how ILSS was diminished in both CFRP and ZT-CFRP samples with matrix degradation caused by extreme temperature exposure. Test samples were heated to 350 ˚C for 10 minutes and then allowed to return to room temperature. SBS testing in accordance with ASTM D2344 was conducted on both untreated and heat-treated samples for comparison. All samples were at room temperature during testing. It was found that ZT-CFRP samples (with 0.5wt% CNF concentration the matrix) exhibited higher ILSS with and without heat treatment over the traditional CFRP samples with and without heat treatment by +33.96% and +25.12%, respectively. ZT-CFRP ILSS was found to decrease by 10.584 MPa (-14.56%) after the extreme heat treatment, while CFRP ILSS decreased by only 4.627 MPa (-8.53%). Microscopic image analysis was also performed to provide insight into how the CNF z-threads may have provided a mechanism for retaining ILSS performance even with matrix thermal degradation. 
    more » « less
  5. ; ; ; (, CAMX 2023 Technical Proceedings)
    Previous studies have provided evidence that reinforcement of epoxy adhesives with nanostructures such as carbon nanofibers (CNFs) produces higher strength bonded joints between carbon fiber reinforced polymer (CFRP) laminates and shifts bond-line failure modes from the adhesive into the laminate. Despite this, there has been no research dedicated to applying reinforced adhesives to the bonding of nano-reinforced CFRP such as CNF z-threaded carbon fiber reinforced polymer (ZT-CFRP) laminates, which have been proven to exhibit increased interlaminar shear strength, mode-I delamination toughness, and compressive strength over traditional CFRP. This study examined the effectiveness of using CNF reinforced epoxy adhesives for unidirectional ZT-CFRP laminate bonding through single-lap shear tests using the ASTM D5868-01 standard. Unidirectional CFRP laminate samples bonded with both epoxy adhesive and CNF reinforced epoxy adhesive were also tested for comparison. It was found that the average shear strength observed for ZT-CFRP samples bonded with CNF reinforced epoxy adhesive was approximately 44% and 26 % higher than that of CFRP samples bonded with epoxy adhesive and CNF reinforced epoxy adhesive, respectively. Microscopic image analysis was performed to examine the mode of bond failure. The roles of nanomaterials in the fracture mechanism of the adhesives and the composite laminates are also discussed. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email