Browsing by Author "Liu, Haibao"
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Item Open Access Comparison of different quasi-static loading conditions of additively manufactured composite hexagonal and auxetic cellular structures(Elsevier, 2022-12-27) Zhou, Jin; Liu, Haibao; Dear, John P.; Falzon, Brian G.; Kazancı, ZaferAuxetic cellular structures have the potential to revolutionise sandwich panel cores due to their potential superior energy absorption capability. Because of their negative Poisson's ratio, auxetics behave counterintuitively and contract orthogonally under an applied compressive force, resulting in a densification of material in the vicinity of the applied load. This study investigates three cellular structures and compares their compressive energy absorbing characteristics under in-plane and axial loading conditions. Three unit cell topologies are considered; a conventional hexagonal, re-entrant and double arrowhead auxetic structures. The samples were additively manufactured using two different materials, a conventional Nylon and a carbon fibre reinforced composite alternative (Onyx). Finite element simulations are experimentally validated under out of and in-plane loading conditions and the double arrowhead (auxetic) structure is shown to exhibit comparatively superior energy absorption. For the carbon fibre reinforced material, Onyx, the specific energy absorbed by the double arrowhead geometry was 125% and 244% greater than the hexagonal (non-auxetic) and re-entrant (auxetic) structures respectively.Item Open Access Damage and energy absorption behaviour of composite laminates under impact loading using different impactor geometries(Elsevier, 2023-06-24) Ding, Yuzhe; Liu, Jun; Hall, Zoe E. C.; Brooks, Richard A.; Liu, Haibao; Kinloch, Anthony J.; Dear, John P.The present paper compares the damage and energy absorption behaviour of composites subjected to low-velocity impact using different frontal geometries for the impactor, with the composites possessing a layup of [02/902]2s. In this study, the rigid impactors with either round-nosed or flat-ended frontal geometry are employed to perform drop-weight tests at various impact energies ranging from 10 to 30 J. The measured loading response and energy absorption are analysed and compared. Additionally, the types and extent of impact-induced damage in the composite specimens are assessed via ultrasonic C-scan, optical microscopy (OM) and scanning electron microscopy (SEM) studies. It is shown that the impact energy threshold for damage initiation is greater than 20 J when using the flat-ended impactor but is less than 10 J when using the round-nosed impactor. In both cases, delamination initiates between the plies in the composite laminate. However, for the flat-ended impactor, the damage behaviour of the fibres exhibits kinking fracture, which differs from the pull-out fibre-fracture caused by the round-nosed impactor. These differences in behaviour are attributed to impactor/composite contact geometry effects which leads to different extents of indentation damage, which in turn directly affects the degree of delamination and fibre damage in the composite.Item Open Access Effects of contact friction and ply blocking on the crush behaviour of thin-walled composite structures: a numerical study(Elsevier, 2022-10-18) Liu, Haibao; Zhou, Jin; Zhang, Di; Li, Shipeng; Giannopoulos, Ioannis K.The present paper presents a three-dimensional composite damage model for predicting the crush response of thin-walled structures, i.e., cylindrical tubes, manufactured employing fibre-reinforced polymer–matrix composites. This computational model is based upon a Continuum Damage Mechanics (CDM) approach and accounts for both the intralaminar and interlaminar damage as well as nonlinear behaviour that occur in the composite materials. Experimental data, obtained from published literature, are employed to validate the proposed composite damage model. A comparison between the experimental and computationally predicted results, including the load response, energy absorption and damage morphology, shows good agreement. Subsequently, the validated computational model is employed to investigate the effects of contact friction and ply blocking on the crush response of thin-walled composite structures. The results reveal that the friction between the tube/platen surfaces has a positive effect on the crushing performance of the composite structures and the ply blocking can somehow inhibit the crushing performance of the investigated composite structures.Item Open Access Effects of fiber orientation on tool wear evolution and wear mechanism when cutting carbon fiber reinforced plastics(Elsevier, 2022-09-07) Wu, Weizhou; Li, Shipeng; Qin, Xuda; Liu, Wentao; Cui, Xin; Li, Hao; Shi, Mengrui; Liu, HaibaoThe aim of the present paper is to reveal the influence of different fiber orientations on the tool wear evolution and wear mechanism. Side-milling experiments with large-diameter milling tools are conducted. A finite element (FE) cutting model of carbon fiber reinforced plastics (CFRP) is established to get insight into the cutting stress status at different wear stages. The results show that different fiber orientations bring about distinct differences in the extent, profile and mechanism of tool wear. Severer wear occurs when cutting 45° and 90° plies, followed by 0°, correspondingly, the least wear is obtained when θ = 135° (θ represents the orientation of fibers). Moreover, the worn profiles of cutting tools when θ = 0° and 45° are waterfall edge, while round edge occurs when θ = 135° and a combined shape of waterfall and round edge is obtained when θ = 90°. The wear mechanisms under different fiber orientations are strongly dependent on the cutting stress distributions. The evolution of tool wear profile is basically consistent with the stress distribution on the tool surface at different wear stages, and the extent of tool wear is determined by the magnitude of stress on the tool surface. Besides, the worn edges produce an actual negative clearance angle, which decreases the actual cutting thickness and leads to compressing and bending failure of fibers beneath the cutting region as well as low surface qualities.Item Open Access Fracture behaviour of fibre-reinforced composite materials subjected to shear loading: an experimental and numerical study(Elsevier, 2022-09-09) Liu, Haibao; Zhou, Jin; Kong, Xiangshao; Li, ShipengCompared to fibre-dominated behaviour, a response dominated by the matrix under shear loading can considerably limit the load-bearing capability and restrict the utilisation of composite materials. It is therefore practically significative to understand the shear response of composite materials. This paper presents a detailed experimental and numerical investigation on the fracture behaviour of composite laminates subjected to shear-dominated loading. Composite specimen with a lay-up of [(0/90)4/0]S are tested using the V-Notched Rail (VRS) shear test method. Subsequently, the Scanning Electron Microscope (SEM) investigation is also conducted on the fracture surfaces of the tested specimens to get insights into the damage mechanisms due to shear loading. In addition, a high-fidelity computational damage model is developed to predict the shear fracture behaviour of fibre-reinforced composites. Simulation results, including loading response, strain distribution and shear fracture, well correlated with experimental results, which demonstrates the predictive capability of the developed elastic-plastic damage model.Item Open Access Impact testing on the pristine and repaired composite materials for aerostructures(MDPI, 2023-04-12) Hall, Zoe E. C.; Liu, Jun; Brooks, Richard A.; Liu, Haibao; Dear, John P.Aircraft technologies and materials have been developing and improving drastically over the last hundred years. Over the last three decades, an interest in the use of composites for external structures has become prominent. For this to be possible, thorough research on the performance of composite materials, specifically the impact performance, have been carried out. For example, research of impact testing for pristine carbon-reinforced epoxy composites mentions matrix cracks, fibre fracture, and delamination as the failure modes that require monitoring. In addition, thorough testing has been carried out on composites repaired with an adhesive bond to observe the effects of conditioning on the adhesively bonded repair. The results suggest there are no major changes in the adhesive under the testing condition. By reviewing the impact testing on the pristine and repaired composite materials for aerostructures, this paper aims to illustrate the main findings and also explore the potential future work in this research scope.Item Open Access Optimization of multi-tooth milling tool for interlaminar damage suppression in the milling of carbon fiber–reinforced polymers(Springer, 2022-05-27) Liu, Jian; Tang, Xinkai; Li, Shipeng; Qin, Xuda; Li, Hao; Wu, Weizhou; Srijana, Yadav; Liu, Wentao; Liu, HaibaoCarbon fiber–reinforced polymers (CFRP) are widely utilized in the aerospace field due to their significant specific strength, specific modulus, and strong design ability. However, anisotropy and low interlaminar bonding strength lead to burr, tear, lamination, and other damages in CFRP machining. In this paper, a 3D finite element model for the milling of CFRP was carefully developed, and the cutting forces, the interlaminar stress, and the interlaminar damage were properly obtained. Typically based on the developed model, the effects of geometric parameters of the multi-tooth milling tool were precisely analyzed. Next tool geometries were optimized for suppressing the interlaminar damage in the milling of CFRP. Results convincingly show that the multi-tooth milling tool with the geometry of 1.4 mm length of the micro tooth, 38.2° left helix angle, 11 left-handed chip grooves, 15° right helix angle, 12 right-handed helix grooves, approximately rectangular of section shape of the chip groove, 10° rake angle, and 15° clearance angle efficiently delivers the optimal performance. Besides, cutting performance of numerous coated tools was also studied. Results typically show that the multi-tooth milling tool with a diamond coating maintains significant advantages in aspects of the tool life and costs compared with the uncoated and diamond-like carbon coating (DLC)-coated tools.Item Open Access A review of high‐velocity impact on fiber‐reinforced textile composites: potential for aero engine applications(Wiley, 2022-04-02) Li, Yinghong; Chen, Xuefeng; Zhou, Jin; Liu, Xiaochuan; Zhang, Di; Du, Feiping; He, Weifeng; Jia, Pu; Liu, HaibaoConsiderable research has indicated that fiber-reinforced textile composites are significantly beneficial to the aerospace industry, especially aero engines, due to their high specific strength, specific stiffness, corrosion resistance, and fatigue resistance. However, damage caused by high-velocity impacts is a critical limitation factor in a wide range of applications. This paper presents an overview of the development, material characterizations, and applications of fiber-reinforced textile composites for aero engines. These textile composites are classified into four categories including two-dimensional (2D) woven composites, 2D braided composites, 3D woven composites, and 3D braided composites. The complex damage mechanisms of these composite materials due to high-velocity impacts are discussed in detail as well.Item Open Access Strain-rate-dependent mechanics and impact performance of epoxy-based nanocomposites(Elsevier, 2022-12-28) Tüfekci, Mertol; Özkal, Burak; Maharaj, Chris; Liu, Haibao; Dear, John P.; Salles, LoïcStrain-rate-dependent mechanical properties and impact performance of manufactured epoxy-based nanocomposites are investigated. As reinforcements, fumed silica (FS) and halloysite nanotube (HNT) are used alongside Albipox 1000 and Nanopox F700. First, the internal structures of the composites are visualised using scanning electron microscopy (SEM). To identify the strain-rate-dependent mechanical properties, three-point bend tests are conducted at three different strain rate levels. For the impact resistance, Charpy impact tests are performed. For further investigations of the mechanical properties of the composites, mean-field homogenisation (MFH) and finite element (FE) analyses on the representative volume elements (RVE) are performed for each type of composite material. Overall, the modelling and experiments are in good agreement and account for the mechanical behaviour of these epoxy-based nanocomposites.