CONSTITUTIVE MODELLING OF SELF-HEALING EPOXY VITRIMERS

Vitrimers are polymeric materials that behave as thermosets at room temperature but, when heated, they exhibit a plastic flow like thermoplastics, enabling their reprocessability. This reprocessability is particularly appealing for sustainable material design, as it allows damaged components to be repaired or recycled, reducing waste and extending their lifespan. When heated above the glass transition temperature, vitrimer networks undergo dynamic covalent bond exchange, allowing damaged material to recover its original mechanical properties while maintaining its shape. The objective of this study is to present a new constitutive model to computationally predict the mechanical behaviour, damage and healing evolution in materials with self-healing properties. The model is informed by experimental data derived from tailor-made aromatic disulfide-containing epoxy vitrimer samples. The model is formulated at the material point level following thermodynamic principles within a continuum mechanics framework. The damage evolution function depends on thermodynamic forces while the healing function, modelled as reverse damage, is based on the kinetic results of the chemical transformation process of the material. The proposed constitutive model has first been developed and validated at material point level, and then it has been implemented in a finite element framework to enable the computational study of self-healing behaviour in structural components under realistic loading and thermal conditions. Simulations were conducted to observe temperature and stress distributions in a sample subjected to a cyclic sequence of damage-inducing loading, unloading, healing-inducing heating, and a new cycle of reloading and unloading. The results replicate the force-driven mechanical behaviour and temperature-driven self-healing properties of the vitrimer. Validation against both experimental data and literature demonstrates the model’s capability to capture the self-healing material behaviour.