3D-Printed Polymers: What Did Penetration Tests Reveal?

Understanding how 3D-printed polymers behave under impact matters both for materials engineering and for recognizing risks when printed parts are used outside ordinary applications. A study at the University of Sarajevo compared five FDM polymers against a wooden target. Its findings show why impact results need careful interpretation—and why a test on wood should not be treated as a direct measure of injury to a person.

Key findings

• The study examined five materials: PLA, Tough PLA, polycarbonate (PC), nylon and PETG.
• The specimens were made using FDM, or fused filament fabrication, a process that deposits heated filament in layers.
• The study recorded specimen mass, launch speed and penetration depth in wooden boards.
• PC failed in two of its three test attempts.
• Tough PLA achieved penetration in all three attempts, while the greatest average penetration depth was reported for the lower-infill PLA specimens.
• Wood was used as a surrogate target; it was not human tissue and cannot establish a clinical injury outcome.

Why this research question matters

Additive manufacturing makes it possible to produce polymer parts from digital designs using a wide range of filaments. Understanding how material choice affects a printed part’s behavior under impact is therefore relevant to engineering and product safety. This particular paper examines potentially hazardous objects, so its findings should be understood as a safety warning and a materials comparison—not as instructions for making or using a projectile.

The paper, by Adi Pandžić, PhD, appeared in the *Journal of Mechanical Science and Technology* in 2023. The work concerns additive manufacturing and the consequences of relying on printed polymers in applications where mechanical behavior and safety are important.

Materials and experimental approach

The study selected five Ultimaker polymers: PLA, Tough PLA, PC, nylon and PETG. The paper describes PLA as widely used and easy to print; Tough PLA as less brittle than standard PLA; PC as strong and tough; nylon as durable and ductile; and PETG as tough and wear-resistant. These descriptions provide background for the comparison, but they cannot by themselves predict how a particular printed part will perform in an impact test.

The specimens were produced with FDM. In this process, a printer deposits heated filament in successive layers. The finished part’s behavior can depend on the material and the bonds between layers. The paper reports that the specimens were printed in an edgewise orientation. The study reports that the specimens were weighed, their speed at launch was measured and their penetration into the wooden boards was recorded. Three specimens were tested for each material, with three additional PLA specimens made at a lower infill. Infill is the material inside a printed part’s outer walls; its density affects how much material occupies the interior.

The study used separate wooden boards for the material groups and aimed at different positions on the boards to reduce the influence of local variations in the wood. Wood was selected as a skin surrogate based on prior research, but that choice does not make wood equivalent to human tissue. A result against a wooden board cannot, on its own, establish what would happen in a real injury.

What the results showed

The findings did not support a simple assumption that a stronger material will always penetrate farther. The paper reports that stronger materials left larger damage at the impact point, while some less-strong materials achieved greater penetration depth. These are different measures of impact behavior: the size of the damaged area and the depth of penetration do not describe the same outcome.

Among the reported comparisons, the lower-infill PLA specimens had the greatest average penetration depth. Tough PLA stood out because all three tested specimens achieved penetration. PC presented a repeatability issue, with two of its three attempts failing. These observations apply to the specimens and test conditions in this paper. They do not show that every part printed from a given filament will behave the same way; FDM results can vary with part geometry, layer orientation and production conditions.

The paper also calculated measures related to energy and contact area and compared them with values reported in earlier research on skin penetration. However, the target in this experiment was wood, not human tissue, and comparing results with earlier publications is not the same as directly testing an injury. For safety reasons, this article does not reproduce energy values or operational parameters of the testing apparatus.

Practical meaning for engineers and students

For engineers and product designers, the central lesson is that a polymer’s name alone is not enough to predict a finished part’s impact behavior. Infill and layer orientation can matter, and different measures of damage may point to different conclusions. A safety-focused product assessment needs to define the intended use, relevant test conditions and suitable acceptance criteria. This paper is not a standardized safety certification for a product.

For students and researchers, the study offers a case of experimental material comparison and a useful example of how to discuss limitations. Three specimens per material is a small sample for broad generalization. The failed PC attempts also underline the need to distinguish a material’s behavior from the reliability of a test. Results against one target type cannot automatically be transferred to metal, animal skin or human tissue.

Limitations and future work

The paper presents the work as a basis for further research. Limitations include the small number of specimens, the use of a wooden target and the selection of specific polymers from one manufacturer. The study was not a direct injury assessment and did not cover every FDM material. Its conclusions should therefore remain tied to the specimens and experimental conditions described in the paper.

The paper mentions future work involving other target materials and further optimization of design and printing. Any such research calls for careful risk management and appropriate laboratory and safety procedures. The results should not be used as a guide to producing or improving hazardous objects.

Conclusion

This study found different impact behavior among five FDM polymers tested against a wooden target, and showed that material strength alone does not explain penetration depth. PLA, Tough PLA, PC, nylon and PETG produced different outcomes, with some attempts also showing limitations in repeatability. The paper’s main contribution is a comparison of printed materials alongside a clear safety concern: 3D-printed polymers can present serious risks in certain circumstances. Its findings are best read as materials research with important limitations, not as a practical guide to making or using projectiles.

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Author: Adi Pandžić, PhD in Mechanical Engineering

This article summarises a published research paper; please refer to and cite the original paper. About the author

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