Mechanical Response of Epoxy Resin-Flax Fiber Composites Subjected to Repeated Loading and Creep Recovery Tests

• Published in: Polymers Vol. 15; no. 3; p. 766
• Main Authors: Stochioiu, Constantin, Hadăr, Anton, Piezel, Benoît
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.02.2023; MDPI
• Subjects: Comparative analysis; Composite materials; Creep recovery; Energy requirements; Engineering Sciences; Epoxy resins; Fiber reinforced plastics; Fiber reinforcement; Flax; Load; Mechanical analysis; mechanical characterization; Mechanical properties; Repeated loading; Strain gauges; Stress; Tensile stress; Tensile tests; Viscoelasticity; viscoplasticity; Yield point; France; viscoplasticity; fiber-reinforced plastics; mechanical characterization; viscoelasticity
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym15030766

Flax fiber-reinforced plastics have an innate eco-friendly nature due to the fiber reinforcement and reduced energy requirements in fabrication when compared to current fiber reinforced composite materials. They possess a complex time-dependent material behavior, which is investigated in the present paper. A composite material with flax fiber reinforcement on the load direction, embedded in an epoxy resin matrix, was studied. The procedures used were tensile tests, repeated loading-recovery, and creep-recovery tests, which were meant to expose the components of the response with respect to stress level and load duration. The results showed an elastic bi-linear behavior, a yield point at approximately 20% of the ultimate tensile stress, and tensile moduli of 35.9 GPa and 26.3 GPa, before and after yield. This is coupled with significant non-linear viscoelastic and, after yield, viscoplastic components, accounting for up to 14% of the strain response. The behavior is inherited from both the matrix and the fiber reinforcement and is attributed to the amorphous nature of the matrix combined with the microstructural re-organization of the fiber under load, which are partially reversible.