•Fatigue properties of 3D printed polymeric materials are reviewed.•Raster angle of +45°/−45° gives long fatigue life in PLA and ABS-printed materials.•FDM parameters should be optimised in relation ...to material characteristics.•In FDM, fibre properties are important determinants for fatigue life.•For ACM, cellular geometry and bulk material properties govern fatigue performance.
Polymer-based materials are increasingly produced through fused deposition modelling (FDM) – an additive manufacturing process, due to its intrinsic advantages in manufacturing complex shapes and structures at low overhead costs. The versatility of this technology has attracted several industries to print complex geometrical structures. This underlines the importance of studying the mechanical strength of FDM printed polymeric materials, especially their fatigue behaviour in cyclic loading conditions. Conventionally manufactured polymeric materials (e.g. injection moulding) have superior fatigue performance than FDM printed materials. Unlike conventionally manufactured polymers, FDM-made polymers have layer by layer adhesion and the influence of printing parameters make fatigue analysis complex and critical. The influences of printing parameters and printing material characteristics have a significant impact on the fatigue behaviour of these materials. The underlying mechanism behind the fatigue of FDM printed polymers is crucial for the assessment of these materials in structural applications. However, the fatigue behaviour of FDM printed polymeric materials has not been reviewed in detail. Therefore, this article aims to evaluate 3D printed polymeric materials’ fatigue properties. The importance of fatigue in the FDM printed biomedical materials is also reviewed, and more importantly, the novel FDM printed architected cellular material fatigue properties are also introduced.
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•The quasi-static compression response and fatigue behavior of the graded structure are investigated;•The gradient direction and sandblasting affect the mechanical responses of the ...graded structure;•The mixture rule can preferably predict the mechanical properties of graded structure.
Graded lattice structures have been paid wide attention in the engineering and biological fields due to their excellent energy absorption capacity and variable porosity characteristics. Based on the size-graded lattice structure, laser powder bed fusion is utilized to manufacture the corresponding Ti-6Al-4 V lattice samples. Then, the quasi-static compression experiment is conducted and a predictive model for its mechanical properties is established accordingly. Also, its dynamic fatigue behavior is studied, and the influence of sandblasting and gradient direction on its mechanical response is evaluated. The results show that excellent mechanical properties and energy absorption capacity is exhibited in the vertical graded (VG) structure. Compared to the uniform structure, its elastic modulus and energy absorption are increased by 17.53% and 59.43%, respectively. The compression response of the radial graded (RG) structure is similar to that of the uniform structure, with minor changes on the mechanical properties and energy absorption capacity. However, the fatigue performance of the RG structure is better than that of the VG structure. With appropriate mechanical properties and changes in pores, this graded structure can simulate the changing physical and chemical properties of natural bone. Therefore, it has great potentiality in the application of bone implants.
Basalt fibre-reinforced polymer (BFRP) bar-reinforced seawater sea-sand concrete (SSSC) structures have long-term development significance. However, there have been few systematic studies on the ...fatigue bond behaviour between BFRP bars and SSSC. Therefore, to fully understand the fatigue bond mechanism of BFRP bar-reinforced SSSC structures, the fatigue bond performance between BFRP bars and SSSC was thoroughly studied. Fatigue pull-out tests were conducted to study the influence of the concrete strength, bar diameters, surface shapes of BFRP bars, and stress levels on the fatigue bond behaviour. It was found that the total slip could be regarded as an inherent property of the bond between BFRP bars and SSSC, which had nothing to do with the loading process. Furthermore, the bond fatigue failure mode had great influence on the fatigue bond indexes, including the fatigue bond stiffness, slip at maximum fatigue bond stress, and residual fatigue slip. A fatigue bond model was proposed to reflect the fatigue bond behaviour. Meanwhile, a design method was proposed for predicting the fatigue life based on the slip at maximum fatigue bond stress. Finally, according to different surface shapes of BFRP bars, the fatigue bond mechanism between BFRP bars and SSSC was classified and discussed.
•Fatigue bond performance between BFRP bars and SSSC was thoroughly studied.•Total slip could be regarded as an inherent property of bond.•The fatigue bond failure mode had great influence on the fatigue bond indexes.•A fatigue bond model was proposed to reflect the fatigue bond behaviour.•A design method was proposed for predicting the fatigue life.
The Additive Manufacturing process, namely the Laser Powder Bed Fusion, enables the 3D printing of components in Aluminum alloys, such as AlSi10Mg. The Aluminum alloys are widely used in aeronautical ...and automotive industries, whereby it is fundamental the understanding of in-service fatigue behavior. As it is well known the geometrical discontinuities generate stress concentrations that have impact in the fatigue life of the components. In this sense, this work pretends to study the fatigue of notched and unnotched samples of AlSi10Mg manufactured by LPBF under variable loading amplitudes, once most of in-service components are subjected to both these effects. The best achievements of this work were the following: the applied heat treatment generates a better performance for high cycle fatigue for both cases. Some fatigue life prediction models based on the accumulated damage were applied obtaining a good agreement with the experimental results.
This paper evaluates the mechanical properties of woven continuous carbon fibre composites printed by additive manufacturing (AM). Comparison mechanical test studies (tensile, flexural and fatigue) ...were carried out with two nonwoven AM printed composites (unidirectional and multidirectional fibres), along with those of both a woven composite, as well as a composite reinforced using chopped carbon fibres. Compared with the 17 MPa tensile strength obtained for the chopped fibre composite, the average strength of unidirectional (nonwoven), multidirectional (nonwoven) and woven fibre composites were 39, 13 and 19-fold higher, respectively. The tensile strength of the woven composites was 52% lower than that attained by the unidirectional (nonwoven) fibre composites; and 38% higher than the multidirectional (nonwoven) fibre composites. A comparison was also made between the flexural and fatigue performance of the unidirectional (nonwoven) and woven fibre composites. The flexural strength of the latter was approximately 39% lower than the nonwoven composites, however, the load bearing capacity of woven fibre was superior. This performance difference was supported by the fatigue testing results. At 70% of maximum tensile load capacity after 2 × 105 cycles, the nonwoven composites failed, while the woven composites continued to perform until a level of 85% of maximum load capacity was reached. The superior fatigue strength of the AM fabricated woven carbon fibre composites, demonstrates their potential for use in high cyclic load applications.
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•A novel AM technique for the fabrication of continuous carbon fibre woven composites.•A superior load bearing capacity of carbon fibre woven composites established.•Woven fibre composites undergo fatigue test (2 × 105 cycles) without catastrophic failure.•A distinct fatigue fracture behaviour established between woven and nonwoven composites.•Woven composites display superior fatigue performance compared to nonwoven.
•Highlighting the scatter and the statistical size effect of Ti-6Al-4V 4V alloys obtained by the selective laser melting (SLM) process•Quantifying the role of the pore and the as-built surface in ...these effects.•Modelling the size effect by a probabilistic approach that bases on the probability of occurrence of LoF pores.
This work is focused on the influence of defects on scatter and statistical size effect of Ti-6Al-4V alloy fabricated by the SLM process. A vast fatigue test campaign has been undertaken, for two surface conditions (as-built and machined surfaces) and two specimen geometries with different highly loaded volume sizes. It was shown, for machined specimens, that a large variety of crack initiation mechanisms is the principal origin of the fatigue scatter. Regarding the size effect, the change of the mechanism is the first order factor that governs the size effect. For as-built specimens, these effects are much less pronounced.
This study investigates the fatigue behaviour of 316L stainless steel manufactured by laser powder bed fusion. More specifically, the influence of the microstructure on fatigue is analysed for four ...different material conditions: as-built, stress relieved, fully annealed and hot isostatic pressed. Fully reversed tension-compression fatigue results on miniaturised vertically built and machined samples indicate that as-built and stress relieved specimens exhibit superior fatigue behaviour compared to fully annealed and hot isostatic pressed ones. Fine sub-grained cellular microstructure in as-built and stress relieved samples resulted in high fatigue performance, which was decreased with microstructure coarsening from the high temperature heat treatments. Secondly, a microstructure-based fatigue crack initiation model is adapted for additively manufactured 316L and verified for different material states. The results show that the analytical model depicts a conservative prediction for crack initiation life when compared with experimental results for full fracture. This validation offers the potential to expand the model for other material and process conditions.
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•Additively made 316L shows superior fatigue behaviour with cellular microstructure.•Microstructure coarsening from heat treatments lowers the fatigue performance.•Microstructure-based crack initiation model is adapted for additively manufactured 316L.•The model offers prediction potential for other process & post-treatment conditions.
Natural fibre reinforced composites (NFRCs) offer a sustainable and environmentally friendly alternative to composites made from synthetic reinforcements, with their response to dynamic loading ...phenomena being of utmost importance for structural applications. Herein, flax fibre reinforced epoxy composites and their glass fibre reinforced hybrid counterparts were developed benefiting from synergic effects of hybridisation between flax and glass fibres with the aim of achieving optimised fatigue behaviour. In order to study the fatigue behaviour, three different types of composite laminates comprised of flax fibres only, and two hybrid flax-glass configurations were fabricated, with alternating flax/glass reinforced layers. The hybrid effects on the fatigue behaviour of all the composite laminates were investigated by using constant ratio R under a tension–tension fatigue loading. The investigated fatigue behaviour showed promising performance in the hybrid laminates, with a great effect of the hybrid configuration on the fatigue life. The hybrid laminate with alternating layers of flax and glass demonstrated the best performance under fatigue, showing a good damage accumulation indicator; about 7 times greater, as compared to the other two laminates. The statistical analysis performed indicated that the aforementioned laminate has a less probability of failure, i.e. it will fail in a greater number of fatigue cycles, as compared to the other two laminates. The influence of various parameters such as fabrication induced defects, fibre matrix interface on the fatigue life has been further characterised using imaging techniques. The findings of this study significantly contribute towards the exploitation of natural fibre reinforced composites and their hybrids to understand the damage mechanisms that take place during fatigue loadings and how the fabrication-related defects have an influence on the overall performance of those structures in load-bearing applications.
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