HUN-REN-BME Research Group

Development and structural investigation of 3D printed polymer composites with in-situ foamed core material

Project ID:

K 146236

Supported by:

Hungarian National Research, Development and Innovation Office (NKFIH)

Term:

1 January 2024 - 31 December 2027

Supervisor (BME):

Prof. Dr. Tibor Czigány
Dr. Márton Tomin

Participant researchers (BME):

Prof. Dr. Tibor Czigány
Dr. Márton Tomin
Dr. Norbert Krisztián Kovács
Norbert László Lukács
Dr. Péter Tamás-Bényei
Bence Szederkényi
Péter Sántha
Dr. Csenge Tóth

Project summary

The aim of the project is to develop and test composite sandwich structures using additive manufacturing techniques, in which a fiber-reinforced shell layer and a porous foam core layer are produced in a single process step by fused filament fabrication 3D printing. The primary objectives of the project are to investigate the effects of fiber length distribution, reinforcing fiber content and the use of recycled fibers in different types of matrix materials, and to explore the effects of short and long fiber reinforcements. In addition, we aim to develop in-situ foamable filaments by investigating the applicability of different chemical and physical blowing agents, with a particular focus on thermally expandable microsphere-filled biopolymer filaments. The research will analyse the influence of printing parameters such as temperature, printing speed and layer height on the foaming dynamics and the cell structural properties (cell size distribution, cell density) obtained. By optimising the printing parameters, it will be possible to produce cell structures that contribute to improving the mechanical properties of the foam and enhancing the energy absorption capacity. Based on this understanding, it will be possible to produce functional structures with controlled varying porosity along the cross-section, which not only provide high energy absorption capacity, but also modify the other mechanical properties of the structure (e.g. stiffness, strength) in a favourable direction. This allows the development of unique, tailor-made solutions to meet different industrial needs, for example in the automotive industry, where lightweight but strong structures are important, in medical technology, where porous structures are often used as bone substitutes, or in sports equipment, where the main goal is to increase the shock absorbing efficiency of protective equipment. The use of recycled fibers and the reduction in weight through targeted porosity and the associated improvement in functionality also contribute to reducing the environmental footprint.

Project results

Section 1

1 January 2024 - 31 December 2024

In the first year of the research, we investigated the relationship between microstructure and mechanical properties for material extrusion–based 3D-printed composites. Short glass, basalt, and carbon fiber–reinforced polylactic acid filaments were produced, then, micromechanical models were used to predict the in-plane tensile properties. We found that interlayer tensile properties are strongly influenced by fiber–matrix adhesion. A second-order relationship describes interlayer tensile strength in relation to fiber content between 5 and 25 w%, with a maximum at 15 w%, for carbon and basalt fiber–reinforced composites. If adhesion is weak, the crack propagates along the fiber–matrix interface, causing brittle fracture and low strength. Our results showed the role of fiber–matrix adhesion quality on tensile properties, which has a major impact on both the accuracy of predictions and the damage processes. In addition, we have started to develop in-situ foamable filaments using a two-step manufacturing technology. Using low-temperature compounding followed by filament winding, we investigated the applicability of different physical and chemical blowing agents and their sensitivity to pre-foaming. In addition, preliminary experiments were carried out to investigate the influence of printing parameters, in particular printing speed and temperature, on the resulting cellular structure. We have found that printing temperature above a certain threshold leads to collapse of the cells due to the reduced melt strength and higher diffusivity of the gas, while below this optimum, the expansion is limited.

Section 2

1 January 2025 - 31 December 2025

Section 3

1 January 2026 - 31 December 2026

Section 4

1 January 2027 - 31 December 2027

Project-related publications

Tóth Cs., Molnár K., Virág Á. D.: Short fiber reinforcement in material extrusion 3D printing: A meta-analysis review with insights into sustainable alternatives. Polymer Composites, , 1-39 (2025) https://doi.org/10.1002/pc.29850 IF=4.8 Q1
Tóth Cs., Ilinyi B., Kovács L.: Layer-level constitutive material model for representing non-linear stress-strain relationships in continuous carbon fiber-reinforced 3D-printed composites. Polymer Testing, 146, 108794/1-108794/1-12 (2025) https://doi.org/10.1016/j.polymertesting.2025.108794 IF=5 D1
Tóth Cs., Lukács N. L., Kovács N. K.: The role of the fiber–matrix interface in the tensile properties of short fiber–reinforced 3D-printed polylactic acid composites. Polymer Composites, , 14 (2024) https://doi.org/10.1002/pc.28720 IF=4.8 Q1
Tomin M., Lukács N., Berezvai Sz.: Development of density-graded sandwich structures with in-situ foaming filaments in additive manufacturing. in 'FOAMS 2024 King of Prusia. 2024.09.17-2024.09.20.,7 (2024)