Chapter 4 - A modular concept for the solid-state healing of polymer resins and composites

Abstract

Listen

Translate article

The overarching goal of this chapter is to describe an intelligent solid-state self-healing system that has the ability to detect damage, prognosticate the severity of the damage, and initiate self-healing in a composite structure based on this prognosis without any direct external intervention. The intelligent self-healing system is comprised of three interacting modules: damage sensing, damage prognosis, and self-healing. The main challenges for the intelligent self-healing system are the damage detection capability and the healing initiation before the damage becomes irreversible. Using the damage-sensing and self-healing approach, early initiation of damage can be assessed, and predictive self-healing can be performed by triggering the healing process at the right time and location before irreparable damage occurs. As a proof-of-concept, an analytical solution was developed for a self-healing double cantilever beam (DCB) used for Mode-I fracture testing, where the DCB beam was modeled as a cantilever beam on an elastic foundation. Bilinear traction–separation cohesive law was employed to model crack separation and simulate the cohesive damage zone near the crack tip. Based on the analytical solution, the critical crack initiation loads and damage zone lengths were calculated for the DCB, before and after healing. The cohesive parameters required to specify the traction–separation law were determined experimentally using the J-integral approach for the virgin (i.e., prior to healing) fracture case, as well as after healing. Using the experimentally determined cohesive parameters as input, the analytical solution predicts the damage zone length, the critical transverse stresses along the beam, crack tip displacement, and critical fracture loads. Detailed benchmark comparisons were made by comparing with the experimental and finite element results. Comprehensive parametric studies were performed on the crack growth response and the damage zone length, revealing their relations to the delamination length and other cohesive parameters. Upon model validation, the analytical model was then employed to extract cohesive traction–separation laws for the Mode-I fracture of healed DCB specimens where experimental J-integral data might become unreliable.