Fracture behavior of additively manufactured components: A review
Introduction
Additive manufacturing (AM) has shown favorable and unique capabilities and attracted a lot of research interest in the last few years [1], [2], [3], [4], [5]. In this three-dimensional (3D) printing, components have been produced by adding layers of material under computer control. As 3D printing technology proved its benefits, it has been used in a wide range of applications including automotive [6], electronics [7], aerospace [8], dentistry [9], and tissue engineering [10]. Regarding to increasing applications of 3D printing technology, various engineering aspects have been studied in this field [11], [12], [13], [14], [15]. However, further research seems to be necessary according to increasing applications of this rapid manufacturing process.
Literature investigation confirmed that fracture study of different material was an interesting research topic over the years [16], [17], [18], [19], [20], [21], [22]. In this respect, ductile and brittle fracture, and different modes of failure have been investigated. To this aim, fracture mechanics methodology has been used to determine fracture behavior of materials [23], [24], [25], [26]. Utilizing theory of fracture mechanics plays a crucial role in investigation of structural integrity. Indeed, the fracture mechanics approach is beneficial for characterization of materials. In this context, various techniques and methods have been developed to test metallic and polymeric materials which can be used in fracture analysis of 3D-printed parts. Data obtained from fracture mechanics-based tests can be used to evaluate critical loads and determine remaining lifetimes of components. Different experimental practices such as tensile, fatigue, and bending tests have been currently conducted on intact specimens or test coupons with initial notch or pre-crack. For instance, in [27] nonlinear fracture mechanics parameters were used to predict the lifetime of a disk. As a number of modern manufacturing processes have been introduced over the years, analysis of the fracture must be performed for characterization of engineering parts produced by these methods.
Although there are various standards for conventional manufacturing processes, they are not suitable for 3D printing technology. This leads to slow adaptation of 3D printing technology. As 3D-printed parts are produced layer-wise, there is anisotropic properties throughout the parts. Owing to the production process, 3D-printed parts present different mechanical properties and microstructures compared to components fabricated by other processes. Therefore, experimental investigation must be conducted to provide information and to answer the demands. Currently, there is still a knowledge gap in the influence of parameters on failure load and fracture toughness of additively manufactured parts. In order to close this knowledge gap and obtain a desired deformation behavior in 3D-printed structural components, it is necessary to study fracture behavior of these parts. In a few researches, fracture toughness of 3D-printed rock-like material has been reported [28], [29]. For instance, in [28] digital image correlation technique was used to determine mechanical behavior of circular 3D-printed rock-like specimens. In fact, by a series of tests, the influence of specimen geometry and flaw shapes on load carrying capacity of the examined specimens was reported.
In the present study, we focus on fracture of polymeric and metallic 3D-printed components. In detail, the current study aims at evaluating the fracture behavior and fracture toughness of additively manufactured polymeric and metallic parts. In this context, fracture mechanics methodology was considered in the reviewed papers. Here, we documented and discussed the reported results in experimental tests in fracture studies of above mentioned materials. Mechanical and material properties like strength and fracture toughness play an important role in performance of 3D-printed parts. Therefore, we have considered these parameters in review of the previous studies. The rest of this paper is organized as follows, where Section 2 presents an overview of AM technology. In Section 3 mechanical fracture in polymeric and metallic 3D-printed parts has been comprehensively reviewed. Moreover, fractography of 3D-printed components has been presented. Challenges and perspectives have been outlined in Section 4. Further, a conclusion has been furnished in Section 5.
Section snippets
Overview of additive manufacturing
AM technology is a layer-by-layer fabrication technology which transform 3D virtual models into physical 3D components. Since its first introduction, it has steadily increasing impact on industrial production. Although AM was primarily targeted for small-scale production, currently it has been skewed toward mass production. According to the ASTM standard [30], AM has been classified into seven classes: (a) BJ: binder jetting, (b) SL: sheet lamination, (c) ME: material extrusion, (d) DED: direct
Mechanical fracture in 3D-printed components
Strength of a structural component can be reduced in the presence of a crack. Structural integrity can be evaluated by different methodologies. Fracture mechanics presents a methodology to study the behavior of cracked components. Constitutive equations can be utilized for prediction of failure in crack-free components, but they are not useful when a component contains a crack or flaw. Using principle of fracture mechanics leads to failure prediction in the solid components including cracks. In
Challenges and perspectives
The quality of the additively manufactured parts depends on several parameters which can be categorized into three main stages: preparatory parameters, printing factors, and finishing items. These factors have different effects on the performance of 3D-printed parts produced by various AM processes. Finding optimized parameters for each special case is one of the current challenges in this field. In this respect, it is necessary to consider various parameters such as design aspects, cost,
Conclusion
The technological advancements and innovations in 3D printing technology have led to developments in this rapid prototyping process. Characterization of 3D-printed components plays an essential role for future developments. In this context, fracture behavior of these parts has been studied over the years. In the current study, we have reviewed fracture behavior of 3D-printed polymeric and metallic parts which have been examined under various experimental practices. Knowledge on the fracture
CRediT authorship contribution statement
Mohammad Reza Khosravani: Conceptualization, Methodology, Writing - original draft, Visualization. Filippo Berto: Writing - review & editing. Majid R. Ayatollahi: Writing - review & editing. Tamara Reinicke: Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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