# Static and Cyclic Mechanical Behavior of 3D-Printed PEEK Under Tensile and Compressive Loads

## TL;DR

This study examines how 3D-printed PEEK behaves under static and cyclic loads, showing its potential for medical implants.

## Contribution

The paper presents the first S-N curve for 3D-printed PEEK under compressive loading and evaluates its fatigue behavior.

## Key findings

- Annealing increased PEEK's crystallinity but reduced tensile strength while improving compression strength and modulus.
- Annealed PEEK specimens showed superior fatigue life, achieving infinite life at 83.3 MPa.
- Thermal imaging revealed that annealed specimens endured higher thermal loads during fatigue testing.

## Abstract

Polyether ether ketone (PEEK) is a high-performance polymer with exceptional mechanical properties, durability and lightweight. 3D printing of PEEK can be very beneficial in the medical industry to manufacture patient-specific implants; however, there is a lack of studies regarding the fatigue behavior of 3D-printed PEEK, especially under compression, which is closely related to its potential applications. This paper investigates the static and dynamic mechanical performance of 3D-printed PEEK. Tensile and compression tests were conducted on specimens with ±45° raster orientation. Annealing at 270 °C for 5 h increased crystallinity from 34.4% to 41.4% yet unexpectedly reduced tensile strength from 60.8 MPa to 47.3 MPa, while increasing Young’s modulus from 2.51 GPa to 3.51 GPa. Micro-CT analysis revealed increased pore size after annealing. Static compression strength showed improvement post-annealing, increasing from 80.1 MPa to 126.7 MPa, with modulus rising from 1.64 GPa to 2.28 GPa. Compression–compression fatigue tests, performed at 5 Hz and 2.5 Hz with stress amplitudes of 70–95% of maximum strength (R = 0.1), enabled the construction of the first S-N curve for 3D-printed PEEK under compressive loading. Annealed specimens exhibited superior fatigue life, with infinite life achieved at 83.3 MPa (70% of static strength). Thermal imaging highlighted the role of temperature in fatigue failure, showing that annealed specimens endured higher thermal loads. These findings support the suitability of 3D-printed PEEK for load-bearing biomedical applications under cyclic compressive loads.