Interlayer bonding strength of 3D printed PEEK specimens

• Published in: Soft matter 2021-05, Vol.17 (18), p.4775-4789
• Main Authors: Liaw, Chya-Yan, Tolbert, John W, Chow, Lesley W, Guvendiren, Murat
• Format: Article
• Language: English
• Subjects: Biomedical materials; Bonding strength; Crystal structure; Crystallinity; Design of experiments; Design parameters; Experimental design; Extrusion; Interlayers; Mechanical properties; Modulus of rupture in bending; Nozzles; Polyether ether ketones; Polymers; Printing; Process parameters; Product development; Regression models; Shear viscosity; Strain; Stress; Temperature; Three dimensional printing
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/d1sm00417d

Recent advances in extrusion-based filament 3D printing technology enable the processability of high-performance polymers. Poly(ether ether ketone) (PEEK) is an important group of high-performance polymer that has been widely used in aerospace, automotive, and biomedical applications. The interlayer bonding strength of 3D printed PEEK is crucial for load-bearing applications, yet studies on 3D printed PEEK are sparse due to processing challenges. In this study, the three-point flexural test is used to study the interlayer bonding strength of 3D-printed PEEK specimens with respect to the printing process parameters, including nozzle temperature, print speed, layer height, and wait-time. A design of experiment (DOE) approach is developed to study correlations between printing parameters and the end-use properties, including flexural stress ( σ f ) and strain at break ( f ), flexural modulus ( E f ), and crystallinity ( χ ). Our results show that the nozzle temperature, layer height, and wait-time significantly affect the interlayer bonding strength, with nozzle temperature being the most influential parameter to enhance interlayer bonding strength indicated by a significant increase in σ f , f , and χ . Thermal annealing post-printing is shown to increase the degree of χ and E f , yet its effect on interlayer bonding strength is minimal, indicating that the interlayer bonding strength is primarily determined during the printing process. This study demonstrates the use of a three-point flexural test integrated with a versatile and robust DOE approach to study the interlayer bonding strength of PEEK to reduce product development time while improving mechanical properties. The interlayer bonding strength of 3D-printed PEEK specimens is studied using a three-point flexural test combined with a design of experiment (DOE) approach to reveal correlations between printing parameters and the end-use properties.