Modelling of viscoplastic properties of epoxy resins in fibre-reinforced unidirectional composites
(2026) Mechanics of Time-Dependent Materials — Vol. 30, n° 1, p. 1-24 (2026)
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- Abstract
- Accurate prediction of the lifetime of unidirectional fibre composites requires a model that captures matrix viscoplasticity across generic loading histories. We propose a compact, rate-dependent hardening law for highly crosslinked epoxies that unifies constant-strain-rate and creep behaviour. The yield stress depends exponentially on accumulated plastic strain and logarithmically on plastic strain rate, and the relationship is analytically invertible for direct use in a finite element code. Parameters are calibrated from compression tests at multiple strain rates and from hold-at-load creep tests; validation is performed on RTM-6 and new 736LT epoxy data. The model reproduces (i) the near-linear σ y-logε trend from pre-yield through softening and hardening, (ii) the time-dependent transition from pre-to post-yield during creep, including the rate surge near softening, (iii) long-term (14.5 h) creep more faithfully than stress-time power laws, and (iv) trends in cyclic, variable-rate, and tensile tests. The resulting, easily calibrated formulation enables robust simulation of matrix vis-coplasticity in composite-scale models, improving durability predictions for load-bearing structures such as pressure vessels and wind-turbine blades.
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Citations
Feyen, V., Breite, C., Chevalier, J., Pardoen, T., & Swolfs, Y. (2026). Modelling of viscoplastic properties of epoxy resins in fibre-reinforced unidirectional composites. Mechanics of Time-Dependent Materials, 30(1), 1-24. https://doi.org/10.1007/s11043-026-09855-7 (Original work published 2026)