Interlayer bonding strength of 3D printed PEEK specimens

Area of Science:

• Materials Science
• Polymer Engineering
• Additive Manufacturing

Background:

• High-performance polymers like Poly(ether ether ketone) (PEEK) are crucial for demanding applications in aerospace, automotive, and biomedical fields.
• Extrusion-based filament 3D printing offers advanced processing capabilities for these materials.
• The interlayer bonding strength of 3D printed PEEK is critical for structural integrity but challenging to achieve due to processing complexities.

Purpose of the Study:

• To investigate the impact of key printing process parameters on the interlayer bonding strength of 3D printed PEEK.
• To establish correlations between printing parameters and mechanical properties (flexural stress, strain, modulus) and crystallinity.
• To optimize the 3D printing process for enhanced PEEK performance.

Main Methods:

• Utilized a three-point flexural test to evaluate interlayer bonding strength in 3D printed PEEK specimens.
• Employed a Design of Experiments (DOE) approach to systematically study the effects of nozzle temperature, print speed, layer height, and wait-time.
• Analyzed flexural properties (stress, strain, modulus) and crystallinity (χ) as outcome measures.

Main Results:

• Nozzle temperature, layer height, and wait-time were found to significantly influence interlayer bonding strength.
• Nozzle temperature emerged as the most critical parameter for enhancing interlayer bonding strength, leading to increased flexural stress (σf), strain at break (εf), and crystallinity (χ).
• Post-printing thermal annealing improved crystallinity (χ) and flexural modulus (Ef) but had a negligible effect on interlayer bonding strength, highlighting the importance of in-process control.

Conclusions:

• Interlayer bonding strength in 3D printed PEEK is predominantly determined during the printing process, not by post-processing treatments like annealing.
• Optimizing printing parameters, particularly nozzle temperature, is essential for achieving superior mechanical properties and reliable performance in load-bearing PEEK applications.
• The integrated approach of three-point flexural testing and DOE effectively characterizes and enhances the interlayer bonding of 3D printed PEEK, reducing development time and improving material performance.