Basalt Fiber-Reinforced Recycled Polypropylene Composites: Adhesive Joints and Aging Performance

Abstract

This study investigates the aging-induced interfacial degradation mechanisms in adhesively bonded single-lap joints (SLJs) fabricated from basalt fiber-reinforced recycled polypropylene (BF/rPP) composites derived from waste materials, with particular emphasis on linking microstructural damage evolution to macroscopic mechanical response. The novelty of the work lies in combining a sustainable BF/rPP system with a systematic correlation among environmental aging, failure morphology, and mechanical performance. Epoxy-bonded joints were subjected to unaged, UV-aged, and hydrothermally aged conditions to simulate accelerated environmental exposure. Tensile testing was used to evaluate mechanical behavior, while scanning electron microscopy (SEM) was employed to identify failure mechanisms. The unaged joints exhibited the highest load-bearing capacity (5732 N) and deformation capability (3.8 mm), governed by cohesive failure, indicating efficient stress transfer across a well-integrated adhesive interface. UV exposure caused only limited reductions in strength (~3%) and displacement (~8%), whereas SEM observations revealed the onset of interfacial degradation accompanied by mixed failure features, including cohesive regions and localized interfacial separation, reflecting early-stage weakening of the adhesive–adherend interface. In contrast, hydrothermal aging resulted in a more pronounced reduction in strength (~16%), governed by moisture- and temperature-induced interfacial degradation. This condition promoted unstable crack propagation through weakened interfacial regions, accompanied by fiber–matrix debonding and localized matrix softening. Although limited ductile deformation features were observed within the adhesive layer, they did not contribute to an improvement in the macroscopic deformation capacity, as premature interfacial failure governed the global response.

Keywords

• Basalt fiber
• Recycled polypropylene
• Adhesive bonding
• Single-lap joints
• Aging performance

Supporting Institution

Scientific Research Projects Coordination Unit (BAP) of Samsun University

Project Number

BAP.MÜF.5501.2023.001

Ethical Statement

Ethics committee approval was not required for this study because it involved no animal or human subjects.

Thanks

This study was supported by the Scientific Research Projects Coordination Unit (BAP) of Samsun University under Project No: BAP.MÜF.5501.2023.001, whose financial contribution is gratefully acknowledged. The authors also sincerely thank the Poelsan R&D team for technical support throughout the project.

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