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This work presents a continuum damage healing mechanics (CDHM) based linear elastic constitutive model for modelling micro-damage initiation and healing phenomena in composite materials with self-healing capability. (Barbero et al., 2005) proposed the CDHM constitutive model for self-healing composite materials, where the healing agent is embedded in the matrix material in form of microcapsules (extrinsic self-healing) and the healing process is triggered by the rupture of a microcapsule. This model uses material with intrinsic self-healing capabilities triggered by heat. Mechanisms such as viscoelasticity and (visco-)plasticity are not considered in this research. Scalar damage and healing evolution laws are taken from (Darabi et al., 2012) while their parameters are adjusted to represent the behaviour of the material used as a matrix. Damage evolution law used in the research is strain rate-dependent and accounts for damage nucleation both during the loading and unloading. CDHM nominal, healing and effective configurations are used. Stress, strain and tangent stiffness tensors in different CDHM configurations are related by means of the strain equivalence hypothesis, what significantly streamlines the numerical implementation of the constitutive model. Thereby, it is important to mention that damage initiation and healing is considered for the matrix material only, whilst no damage is modelled in reinforcing fibres. In this initial phase of the research, an advanced ethylene/methacrylic acid (E/MAA) copolymer, DuPontTM Surlyn R 8940 thermoplastic resin, is used as a self-healing matrix material along with unidirectional carbon fibres as reinforcement. The healing ability of ethylene/ methacrylic acid (E/MAA) copolymer has already been demonstrated for healing of delamination cracks. In this approach, the E/MAA copolymer is located between the carbon fibre/epoxy composite layers, (Pingkarawat et al., 2012). Firstly, the model is developed and validated in Matlab and then implemented into Abaqus user subroutines UMAT and VUMAT. Simple static test cases as well as loading/unloading tests are applied in the validation of the proposed model. The research is carried out in the framework of the ACCESS project (AdvanCed CompositE Selfhealing Simulation), funded by the Croatian Science Foundation (HRZZ). |
