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Volume 19
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10.3390/ma19183935
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Article

Mechanical Properties and Microstructure of Bonded Joints and Hybrid Structures with a 3D-Printed Honeycomb Core Modified with an Epoxy Matrix Filled with Recycled Polyurethane Foam

by
Michal Penc
1,
Miroslav Müller
1,*,
Jiří Marčan
1,
Rajesh Kumar Mishra
1,*,
Jaroslava Svobodová
1,2,
Petr Jirků
1,
Anna Rudawska
3 and
Petr Valášek
1
1
Faculty of Engineering, Czech University of Life Sciences, Kamýcká 129, 165 00 Prague, Czech Republic
2
Faculty of Mechanical Engineering, J. E. Purkyne Universty in Usti nad Labem, Pasteurova 3334/7, 400 96 Usti nad Labem, Czech Republic
3
Faculty of Mechanical Engineering, Lublin University of Technology, Nadbystrzycka 36, 20-618 Lublin, Poland
*
Authors to whom correspondence should be addressed.
Materials 2026, 19(18), 3935; https://doi.org/10.3390/ma19183935
Submission received: 17 August 2026 / Revised: 12 September 2026 / Accepted: 14 September 2026 / Published: 16 September 2026
(This article belongs to the Special Issue Advanced Epoxy Resins and Epoxy-Based Composites)
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Abstract

This article examines the reuse of waste polyurethane foam (PUF) as a material in line with circular economy principles. The main objective was to evaluate how crushed polyurethane filler of different bulk densities—35 kg·m−3 (PUF35), 60 kg·m−3 (PUF60), and their blends at 1–5 wt%—affects the mechanical behaviour and structural integrity of hybrid composite systems and bonded laminated joints. An epoxy resin matrix was combined with 3D-printed polylactide (PLA) honeycomb structures, with rectangular and hexagonal core geometries. Static tensile tests showed that the blended filler (PUF35/60) preserves tensile strength and increases the modulus of elasticity for both core geometries, reaching maximum values at 4 wt% (3.8 GPa for rectangular, 3.6 GPa for hexagonal cores). In bonded lap joints, 1 wt% PUF35 resulted in the highest tensile adhesive bond strength (13.3 MPa). SEM confirmed a high-quality phase interface and continuous adhesive contact between the epoxy matrix and the 3D-printed PLA surface, with dominant cohesive failure and effective mechanical anchoring of foam particles, even near local printing defects. The results confirm mechanically recycled PUF as a promising filler for advanced sandwich structures and adhesive systems.
Keywords: mechanical recycling; polyurethane foam; 3D printing; honeycomb core; epoxy composite; adhesive bond strength; scanning electron microscopy (SEM); bonded joints mechanical recycling; polyurethane foam; 3D printing; honeycomb core; epoxy composite; adhesive bond strength; scanning electron microscopy (SEM); bonded joints
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MDPI and ACS Style

Penc, M.; Müller, M.; Marčan, J.; Mishra, R.K.; Svobodová, J.; Jirků, P.; Rudawska, A.; Valášek, P. Mechanical Properties and Microstructure of Bonded Joints and Hybrid Structures with a 3D-Printed Honeycomb Core Modified with an Epoxy Matrix Filled with Recycled Polyurethane Foam. Materials 2026, 19, 3935. https://doi.org/10.3390/ma19183935

AMA Style

Penc M, Müller M, Marčan J, Mishra RK, Svobodová J, Jirků P, Rudawska A, Valášek P. Mechanical Properties and Microstructure of Bonded Joints and Hybrid Structures with a 3D-Printed Honeycomb Core Modified with an Epoxy Matrix Filled with Recycled Polyurethane Foam. Materials. 2026; 19(18):3935. https://doi.org/10.3390/ma19183935

Chicago/Turabian Style

Penc, Michal, Miroslav Müller, Jiří Marčan, Rajesh Kumar Mishra, Jaroslava Svobodová, Petr Jirků, Anna Rudawska, and Petr Valášek. 2026. "Mechanical Properties and Microstructure of Bonded Joints and Hybrid Structures with a 3D-Printed Honeycomb Core Modified with an Epoxy Matrix Filled with Recycled Polyurethane Foam" Materials 19, no. 18: 3935. https://doi.org/10.3390/ma19183935

APA Style

Penc, M., Müller, M., Marčan, J., Mishra, R. K., Svobodová, J., Jirků, P., Rudawska, A., & Valášek, P. (2026). Mechanical Properties and Microstructure of Bonded Joints and Hybrid Structures with a 3D-Printed Honeycomb Core Modified with an Epoxy Matrix Filled with Recycled Polyurethane Foam. Materials, 19(18), 3935. https://doi.org/10.3390/ma19183935

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