# Modelling of Failure Behaviour of 3D-Printed Composite Parts
## 1 Introduction
Investigation on 3D-printed parts revealed that they have directional properties as well as the material behaviour of the parts is similar to that of laminate composites [16]. Therefore, the mechanics of laminates and laminate theories were proposed for characterizing the mechanical behaviour of 3D-printed parts. Typically, classical first-ply failure criteria were used to assess the laminates' strength. However, strength and safety-oriented failure criteria for design are a more difficult proposition. An alternative to assessing the structural performance of the printed parts is computational modelling. Computational methods [17], such as the finite element (FE) method, are the alternate solutions to experimental work, and further, these computational methods eliminate the challenges associated with experimental work. [PERSON] et al. [18] conducted an FE analysis to investigate the structural performance of printed parts with different infill patterns. The investigations [19] revealed that the material behaviour of the parts is transversely isotropic. The influence of printing parameters on the elastic response of 3D printed arc structures was investigated using FE analysis [20] and found that overlap between the layers significantly influenced the performance of structures. [PERSON] et al. [21] proposed alternate analytical methods for the preliminary design and analysis of 3D-printed parts subjected to uniaxial loading. The vibrational characteristics of 3D-printed parts were assessed using the finite element method [22]. A new computational tool was developed to accurately capture the intricate details of microstructure, which is important in the computational material modelling of 3D-printed parts [23]. The above studies only focused on investigating the macro-level structural performance of 3D-printed parts subjected to different loading conditions and did not consider intricate details of microstructure, which primarily governs the final material behaviour of 3D-printed parts. Computational models based on micromechanical approach considers the microstructure of parts and are useful for determining the material properties and investigating the failure behaviour of 3D-printed parts. Micromechanical computational models employ microstructure, which is built during 3D printing, and the intricate details of microstructure are represented in representative volume element (RVE) or unit-cell for material modelling to estimate the properties. Recently, [PERSON] et al. [24] developed a computational model based on the homogenization technique for investigating the influence of printing strategies on the properties of 3D-printedstructures. Furthermore, the influence of change in microstructure in different sections of 3D-printed parts on the mechanical performance was assessed experimentally and computationally [25]. Several studies employed the computational homogenization method to predict the properties of the printed parts: for PLA material [26], for nanocomposite material [27], for different mechanical loadings [28], and for different printing strategies [29]. [PERSON] et al. [30] developed a computationally efficient micromechanical model based on a unit-cell model to predict the properties of 3D-printed composites. Analytical homogenization was proposed to predict the influence of process parameters on the deformation of 3D-printed parts [31]. [PERSON] et al. [32] developed a multiscale approach based on the nonlinear homogenization method and elastoplastic constitutive law to determine the material behaviour of 3D-printed parts under mechanical loadings. In another study, [PERSON] et al. [33] applied an elastic-plastic homogenization model along with the von Mises failure criterion for investigating the material behaviour of 3D-printed parts. In composite materials, bonding between the fibre and matrix is critical for determining the material behaviour, and this interface is modelled with cohesive-zone modelling in RVEs of 3D-printed parts [34].