Abstract:
This paper presents a series of experiments aimed at deriving the phenomenological constitutive relations for cross-linked polymers. The use of photopolymer materials is accompanied by thermal relaxation transitions, i.e., the glass transition. A model comprising a hypoelastic element and a viscous element is adopted for this class of materials. The hypoelastic element describes the formation of new intermolecular bonds during the glass transition, while the viscous element describes the relaxing processes at a constant temperature. A complete experimental program for identifying the viscoelastic constants is developed and carried out using dynamic mechanical analysis (DMA). The obtained complex modulus is verified and refined based on thermomechanical analysis (TMA). Additionally, a validation experiment is performed on a uniaxial specimen subjected to stepwise loading under heating. The results demonstrated a strong quantitative and qualitative agreement between the calculated and experimental data. A numerical simulation based on the proposed model illustrates the shape-memory effect (SME).
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