Title: Processing and mechanical characterization of short carbon fiber-reinforced epoxy composites for material extrusion additive manufacturing

Abstract

Fiber-reinforced polymer composites have been extensively utilized in recent years as feedstock materials for material extrusion additive manufacturing (AM) processes to improve strength, stiffness, and functionality of printed parts over unfilled printed polymers. However, the widespread adoption of AM of fiber-reinforced polymer composites requires a deeper understanding of the process-structure-property relationships in printed components, and such relationships are not well understood yet. Fiber length is critically important to the mechanical performance of short fiber composites, but very few studies to-date have focused on how the fiber length distribution (FLD) evolves during processing of composite feedstocks and how this evolution affects printing behavior and mechanical properties in 3D-printed composites. Here, FLD is measured for carbon fiber reinforced epoxy composites over a wide range of ink compositions and shear mixing times, and the distributions are fit with a Weibull-type distribution function. The effects of FLD on the tradeoff between ink processability, ink rheology, printing behavior and mechanical properties are investigated. Furthermore, the effects of printing parameters (nozzle size and print speed) on mechanical anisotropy and fiber orientation distribution (FOD) in printed composites are explored. Mechanical properties of printed composites are characterized via 3 pt-flexural testing, and microstructure is investigated using optical andmore » scanning electron microscopy (SEM), and x-ray computed tomography. Finally, the fitted Weibull parameters are fed into a composite model that incorporates FLD and FOD, and model predictions are found to be in excellent agreement with experimental observations.« less

Authors:

Hmeidat, Nadim S.  ^[1];

• Search DOE PAGES for author "Hmeidat, Nadim S."
• Search DOE PAGES for ORCID "0000-0002-9669-0426"

Elkins, Daniel S. ^[2]; Peter, Hutchison R.  ^[2];

• Search DOE PAGES for author "Peter, Hutchison R."
• Search DOE PAGES for ORCID "0000-0003-1026-5830"

Kumar, Vipin  ^[3];

• Search DOE PAGES for author "Kumar, Vipin"
• Search DOE PAGES for ORCID "0000-0002-9580-7098"

Compton, Brett G.  ^[1]

• Search DOE PAGES for author "Compton, Brett G."
• Search DOE PAGES for ORCID "0000-0001-5480-474X"

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+ Show Author Affiliations

1. Univ. of Tennessee, Knoxville, TN (United States)
2. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Thu Jul 08 00:00:00 EDT 2021

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Manufacturing Office; National Science Foundation (NSF)

OSTI Identifier:

1808156

Alternate Identifier(s):

OSTI ID: 1807601

Grant/Contract Number:  

AC05-00OR22725; NA0002839; CMMI-1825815; AC05- 00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Composites Part B: Engineering

Additional Journal Information:

Journal Volume: 223; Journal ID: ISSN 1359-8368

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; additive manufacturing; 3D printing; extrusion; direct ink writing; short-fiber composites; fiber length; thermosets