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

Brubeck L Freeman,Waled F Alnaas,Pedro Bonilla-Villalba,Iulia C Mihai,Anthony D Jefferson

doi:10.1186/s40323-020-00171-4

Brubeck L Freeman, Waled F Alnaas + Show 3 more

Open Access

https://doi.org/10.1186/s40323-020-00171-4

Copy DOI

Abstract

A new specialised finite element for simulating the cracking and healing behaviour of quasi-brittle materials is presented. The element employs a strong discontinuity approach to represent displacement jumps associated with cracks. A particular feature of the work is the introduction of healing into the element formulation. The healing variables are introduced at the element level, which ensures consistency with the internal degrees freedom that represent the crack; namely, the crack opening, crack sliding and rotation. In the present work, the element is combined with a new cohesive zone model to simulate damage-healing behaviour and implemented with a crack tracking algorithm. To demonstrate the performance of the new element and constitutive models, a convergence test and two validation examples are presented that consider the response of a vascular self-healing cementitious material system for three different specimens. The examples show that the model is able to accurately capture the cracking and healing behaviour of this type of self-healing material system with good accuracy.

Highlights

The formation of cracks in quasi-brittle materials such as concrete produces a degradation in mechanical performance in terms of both stiffness and strength
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
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]

Summary

Introduction

The formation of cracks in quasi-brittle materials such as concrete produces a degradation in mechanical performance in terms of both stiffness and strength. We show that the characteristics of the convergence behaviour of the model are the same for the damage only and damage-healing case, but that the error is larger when healing is considered Direct tension test This example considers a set of direct tension tests on doubly notched concrete specimens (illustrated in Fig. 7), which contained embedded healing channels that were filled with cyanoacrylate (CA), presented in Selvarajoo [81] and Selvarajoo et al [82]. It may be seen from the figures that the numerical predictions for the damage only case are able to accurately capture the experimental behaviour in terms of both the load–displacement curve and the predicted crack patterns. The predicted crack patterns are in good agreement

Conclusions

Methods

Findings