A multiscale theory of self-crack-healing with solid healing agent assisted by shape memory effect

• A multiscale theory is developed to model the healing process of SMP matrix embedded with thermoplastic healing agent.
• The molecular healing mechanism under shape recovery pressure is considered.
• Continuum damage mechanics is used to link molecular healing with macro strength recovery.
• The model is implemented in finite element analysis.
• The model is validated per published results in the literature.

Solid healing agents, such as thermoplastic particles, have been widely used in molecular healing of thermosetting polymers, including conventional thermosetting polymers such as epoxy and thermosetting shape memory polymers (SMPs) such as polystyrene. Despite extensive experimental developments in this field, there is an urgent need for healing theories with the ability to correlate molecular level healing events to the bulk scale recovered material properties. A multiscale healing constitutive theory is developed in this manuscript for self-crack-healing composites with embedded solid healing agents. It is assumed that the matrix is made of SMP; and the model accounts for several microscopic healing processes including: (a) rearrangement of free crack surfaces, (b) surface approaching due to shape memory effect, (c) wetting the free surfaces by the molten solid healing agent, (d) diffusion of the solid healing agent, which has been molten upon heating, into the crack surfaces, and (e) randomization. The Continuum Damage Healing Mechanics (CDHM) is utilized to bridge the microscopic and bulk scales. The healing parameters correlate the microscopic level descriptions of the healing to the recovery of bulk material properties. The model is then introduced into the ABAQUS, through user-defined coding, and it is shown that it correlates well with the experimental observations. The developed physically consistent multiscale theory provides material designers with the ability to optimize their self-healing systems via computer aided simulations.