A specialised finite element for simulating self-healing quasi-brittle materials

Abstract

The formation of cracks in quasi-brittle materials such as concrete produces a degradation in mechanical performance in terms of both stiffness and strength. In addition to this, the presence of cracks leads to significant durability problems, such as reinforcement corrosion and calcium leaching [1]. Self-healing systems are designed to mitigate these issues by introducing crack 'healing' mechanisms into the material that result in a recovery of both mechanical performance and durability properties. There is now a significant body of work on the numerical simulation of self-healing systems [2-19], as highlighted in a recent review article [20]. The numerical treatment of damage-healing behaviour in mechanical self-healing models has varied, with many utilising a continuum damage-healing mechanics framework (e.g. [5, 7]). Alternative approaches have included a model based on micromechanical theories [11], the discrete element method (DEM) [13], the extended finite element method (XFEM) [12] and embedded discontinuity elements (EFEM) [17]. In addition to this, the treatment of the healing itself has varied, ranging from treating the healing as a thermodynamic

Numerical Simulation of the Response of Concrete Structural Elements Containing a Self-Healing Agent

“…The damage-based constitutive relation slightly differs from that implemented in recent research. For example, in [ 51 ], the tensile strength of concrete is involved in the damage evolution law, whereas in the present study, the concrete tensile strength is to be matched via the identification of the model constants (please see equation 2). Furthermore, the specimens (for the direct tension test) studied in [ 51 ] contain a predefined notch.…”

“…Recent studies extend the finite element method by proposing a new finite element formulation with embedded strong discontinuity [ 51 ] or by coupling the finite element method (FEM) with the discrete element method (DEM) [ 52 ]. These research works provide intuitive decoupling of two different phenomena: damage accumulation in the initially undamaged materials and initiation and propagation of the macroscopic cracks.…”

“…In Ref. [ 51 ], by hypothesis, the total displacement in the numerical domain is the sum of a component, obtained by linear elastic analysis (of the continuum part), and a jump, associated with the embedded strong discontinuity. The discontinuity presumably follows an elastic-damage cohesive crack constitutive relationship [ 53 ].…”

“…In [ 51 ], by assumption, the shear jump is constant along the discontinuity in each element [ 59 ]. Thus, some shear-dominant problems might require mesh refinement to improve accuracy [ 51 ].…”

“…In [ 51 ], by assumption, the shear jump is constant along the discontinuity in each element [ 59 ]. Thus, some shear-dominant problems might require mesh refinement to improve accuracy [ 51 ]. Equilibrium across the discontinuity and the crack-plane displacements are defined at the element level.…”