This work grew out of rapid developments of topology optimization approaches and emerging industry trends of “3D printing” techniques, the latter bridging to a large extent the gap between innovative ...design and advanced manufacturing. In the present work, we first make an
application-oriented
review of topology optimization approaches in an attempt to illustrate their efficacy in the design of high-performance structures. Subsequently, a broad panorama of additive manufacturing is provided with a particular interest in its application in the automotive and the aerospace sectors. Taking an aerospace bracket as an example, we further go through an entire procedure from topology optimization design to additive manufacturing, then to performance verification. In the interest of cultivating a long-term partnership upon this combination, we finally examine, in face of present and near future, limitations of additive manufacturing in the
loss of geometric accuracy
and
performance deterioration
, and provide a roadmap for future work.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this study, both experimental tests and numerical simulation are implemented to investigate the tensile performance of adhesively bonded CFRP single-lap joints (SLJs). The study considers 7 ...different overlap lengths, 5 adherend widths and 3 stacking sequences of the joints. Three-dimensional (3D) finite element (FE) models are established to simulate the tensile behavior of SLJs. The failure loads and failure modes of SLJs are investigated systematically by means of FE models and they are in good agreement with those of experiments, proving the accuracy of finite element method (FEM). It is found that increasing the adherend width can improve the load-carrying capacity of the joint better than increasing the overlap length does. Moreover, choosing 0° ply as the first ply is also beneficial for upgrading joint's strength. With respect to failure modes, cohesive failure in adhesive and delamination in adherend take dominant, while matrix cracking and fiber fracture only play a small part. With overlap length increasing or adherend width decreasing, cohesive failure takes up a smaller and smaller proportion of whole failure area, but the opposite is true for delamination. SLJs bonded with 0/45/-45/903S adherends are prone to cohesive failure, and 90/-45/45/03S adherends are easy to appear delamination. Both shear and peel stress along the bondline indicate symmetrical and non-uniform distributions with great stress gradient near the overlap ends. As the load increases, the high stress zone shifts from the end to the middle of the bondline, corresponding to the damage initiation and propagation in the adhesive layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
For a long period, phyllotaxis (the arrangement of leaves on a plant stem) has been observed as an interesting morphological property of various plants, and the phyllotactic spirals form a ...distinctive class of patterns in nature. These days, the unique patterns governed by the Fibonacci sequence, or the golden ratio in a deeper sense, have moved beyond the botanical system and came to be universal, occurring in architectural and structural design. In this work, we develop a design approach for curvilinear stiffening ribs which follow the Fibonacci spiral pattern. The parametric model of the designed ribs is built according to two parameters, one discrete and another continuous. Parametric studies on the two variables are performed to assess the potential mechanical advantages of the Fibonacci spiral pattern in stiffening structures. The deformation-, vibration- and buckling-resisting capacities are investigated for thin-walled stiffening plates with a central cutout. Moreover, an attempt is devoted to clarifying the rationality of curvilinear stiffening ribs’ employment in other designs. Lastly, we demonstrate that the developed protocol does not limit itself to planar structures with cutouts, and it is easy to be extended to stiffening ribs on curved surfaces, where the gain in mechanical property is observed to be even more visible and pronounced.
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•A design approach for stiffening ribs following the Fibonacci spiral pattern.•The deformation-, vibration- and buckling-resisting performances are tunable.•Merits of Fibonacci spiral rib reinforced part are demonstrated experimentally.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lightweight lattice structures and chiral metamaterials have both received extensive attention during the past decades. This work builds up a systematic design procedure for an emerging class of ...architected materials, achieving chirality and achirality under the same framework of parameterization. The design of the so-called ‘hyperbolic unit cell’ takes inspiration ultimately from the double-layered morphology of the fore-wing shells of flying beetles, being intended to replicate the hyperbolic geometric feature. The tessellation schemes that populate the microstructure to a component level are stirred up by the similarity with Euclidean tiling of convex regular polygons. Numerical and experimental studies revealed a wide variation of elastic constants for hyperbolic materials maintaining the same volume fraction, making more visible their applications under various loading scenarios, including compression, tension and shear. Also, a significant twisting effect, observed on the chiral cellular material, is shown to be advantageous in the design of buffering plates and energy-absorbing devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
CFRP hybrid bonded–bolted (HBB) joints combine the advantages of traditional joining methods, namely adhesive bonding, and bolting, to achieve optimal connection performance, making them the most ...favored connection method. The structural parameters of CFRP HBB joints, including overlap length, bolt-hole spacing, and fit clearance relationships, have a complex impact on connection performance. To enhance the connectivity performance of joint structures, this paper develops a multiscale finite element analysis model to investigate the impact of structural parameters on the strength of CFRP HBB joint structures. Coupled with experimental validation, the study reveals how changes in structural parameters affect the unidirectional tensile failure force of the joints. Building on this, an analytical approach and inverse design methodology for the mechanical properties of CFRP HBB joints based on deep supervised learning algorithms are developed. Neural networks accurately and efficiently predict the performance of joints with unprecedented combinations of parameters, thus expediting the inverse design process. This research combines experimentation and multiscale finite element analysis to explore the unknown relationships between the mechanical properties of CFRP HBB joints and their structural parameters. Furthermore, leveraging DNN neural networks, a rapid calculation method for the mechanical properties of hybrid joints is proposed. The findings lay the groundwork for the broader application and more intricate design of composite materials and their connection structures.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this study, a novel hybrid metamaterial has been developed via fulfilling hyperbolic chiral lattice with polyurethane (PU) foam. Initially, both the hyperbolic and typical body-centered cubic ...(BCC) lattices are fabricated by 3D printing technique. These lattices are infiltrated in a thermoplastic polyurethane (TPU) solution dissolved in 1,4-Dioxane, and then freeze casting technique is applied to achieve the PU-foam-filling. Intermediate (IM) layers possessing irregular pores, are formed neighboring to the lattice-foam interface. While, the foam far from the lattice exhibits a multi-layered structure. The mechanical behavior of the hybrid lattice metamaterials has been investigated by monotonic and cyclic compressive tests. The experimental monotonic tests indicate that, the filling foam is able to soften the BCC lattice but to stiffen the hyperbolic one, further to raise the stress plateau and to accelerate the densification for both lattices. The foam hybridization also benefits the hyperbolic lattice to prohibit the property degradation under the cyclic compression. Furthermore, the failure modes of the hybrid hyperbolic lattice are identified as the interface splitting and foam collapse via microscopic analysis. Finally, a parametric study has been performed to reveal the effects of different parameters on the compressive properties of the hybrid hyperbolic lattice metamaterial.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Fracture is a very common failure mode of the composite materials, which seriously affects the reliability and service-life of composite materials. Therefore, the study of the fracture behavior of ...the composite materials is of great significance and necessity, which demands an accurate and efficient numerical tool in general cases because of the complexity of the arising boundary-value or initial-boundary value problems. In this paper, a phase field model is adopted and applied for the numerical simulation of the crack nucleation and propagation in brittle linear elastic two-phase perforated/particulate composites under a quasi-static tensile loading. The phase field model can well describe the initiation, propagation and coalescence of the cracks without assuming the existence and the geometry of the initial cracks in advance. Its numerical implementation is realized within the framework of the finite element method (FEM). The accuracy and the efficiency of the present phase field model are verified by the available reference results in literature. In the numerical examples, we first study and discuss the influences of the hole/particle size on the crack propagation trajectory and the force–displacement curve. Then, the effects of the hole/particle shape on the crack initiation and propagation are investigated. Furthermore, numerical examples are presented and discussed to show the influences of the hole/particle location on the crack initiation and propagation characteristics. It will be demonstrated that the present phase field model is an efficient tool for the numerical simulation of the crack initiation and propagation problems in brittle two-phase composite materials, and the corresponding results may play an important role in predicting and preventing possible hazardous crack initiation and propagation in engineering applications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The mechanical behavior of plain woven Carbon Fiber-Reinforced Polymer (CFRP) composites under Three-Point Bending (TPB) is investigated via experimental and numerical approaches. Multiscale models, ...including microscale, mesoscale and macroscale models, have been developed to characterize the TPB strength and damages. Thereinto, Representative Volume Elements (RVEs) of the microscale and mesoscale structures are established to determine the effective properties of carbon-fiber yarn and CFRP composites, respectively. Aimed at accurately and efficiently predicting the TPB behavior, an Equivalent Cross-Ply Laminate (ECPL) cell is proposed to simplify the inherent woven architecture, and the effective properties of the subcell are computed using a local homogenization approach. The macroscale model of the TPB specimen is constructed by a topology structure of ECPL cells to predict the mechanical behavior. The TPB experiments have been performed to validate the multiscale models. Both the experimental and numerical results reveal that delamination mainly appears in the top and bottom interfaces of the CFRP laminates. And matrix cracking and delamination are identified as the significant damage modes during the TPB process. Finally, the quasi-static and dynamic behaviors of plain woven composites are discussed by comparing the results of Low-Velocity Impact (LVI) and TPB simulations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article presents a type of plate Finite Element (FE) models with adaptive mathematical refinement capabilities for modeling laminated smart structures with piezoelectric layers or distributed ...patches. The p-version shape functions are used in combination with the higher-order Layer-Wise (LW) kinematics adopting hierarchical Legendre polynomials. Node-Dependent Kinematics (NDK) is employed to implement local LW models in the regions with piezoelectric components and simulate the global substrate structure with the Equivalent Single-Layer (ESL) approach. Through the proposed NDK FE models, the electro-mechanical behavior of smart structures can be predicted with high fidelity and numerical efficiency, and various patch configurations can be conveniently modeled through one set of mesh grids. Moreover, the effectiveness and efficiency of the NDK FE approach are assessed through numerical examples and its application is demonstrated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Implementation and application of a phase field method for crack propagation simulation in brittle elastic materials.•Investigation of the effects of the loading type (tension and shear), boundary ...conditions, as well as size, location and orientation of the initial crack on the crack propagation path and force-displacement relation in homogenous and linear elastic plates.•Investigation of the effects of the loading type (tension and shear), boundary conditions, bi-material interface, and initial crack location on the crack propagation path and force-displacement relation in linear elastic bi-material plates.•Enhancement of the implementation and application convenience of the phase field method (ParaView as postprocessor, use of the colon function in MATLAB, etc.).
To overcome the difficulties of re-meshing and tracking the crack-tip in other computational methods for crack propagation simulations, the phase field method based on the minimum energy principle is introduced by defining a continuous phase field variable φ (x) ∈ 0,1 to characterize discontinuous cracks in brittle materials. This method can well describe the crack initiation and propagation without assuming the shape, size and orientation of the initial crack in advance. In this paper, a phase field method based on Miehe's approach Miehe et al., Comp. Meth. App. Mech. Eng. (2010) is applied to simulate different crack propagation problems in two-dimensional (2D), isotropic and linear elastic materials. The numerical implementation of the phase field method is realized within the framework of the finite element method (FEM). The validity, accuracy and efficiency of the present method are verified by comparing the numerical results with other reference results in literature. Several numerical examples are presented to show the effects of the loading type (tension and shear), boundary conditions, and initial crack location and orientation on the crack propagation path and force-displacement curve. Furthermore, for a single edge-cracked bi-material specimen, the influences of the loading type and the crack location on the crack propagation trajectory and force-displacement curve are also investigated and discussed. It is demonstrated that the phase field method is an efficient tool for the numerical simulation of the crack propagation problems in brittle elastic materials, and the corresponding results may have an important relevance for predicting and preventing possible crack propagations in engineering applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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