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Author

Lulu Liu

Bio: Lulu Liu is an academic researcher from Nanjing University of Aeronautics and Astronautics. The author has contributed to research in topics: Ballistic impact & Kevlar. The author has an hindex of 8, co-authored 38 publications receiving 177 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the effect of hygrothermal aging on the high speed impact resistance of carbon fiber reinforced composites (CFRP) was investigated using short beam shear tests.

47 citations

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TL;DR: In this paper, three types of multi-phase shear thickening fluid (STF) treated high-strength fabrics were manufactured by adding graphene oxide (GO) and carbon nanotubes (CNTs) to a nanosilica suspension system.
Abstract: The current study focus on the multi-phase Shear thickening fluid (STF) treated high-strength fabrics which is an promising material for soft-wall containment casing. Three types of multi-phase STF were manufactured by adding graphene oxide (GO) and carbon nanotubes (CNTs) to a nanosilica suspension system. Steady rheological property tests and yarn pull-out tests were conducted to determine the shear thickening behavior of the multi-phase STFs and inter-yarn friction of their compound fabrics. Ballistic impact tests were conducted using titanium blade-like projectiles. The energy absorption, deformation evolution and damage patterns were investigated. Tests show that the addition of GO and CNTs resulted in a higher initial viscosity, a lower shear rate for onset of shear thickening and a lower thickening ratio. The enhancement of the frictional force is more striking for multi-phase STFs. The GO additives have the highest deformation in the ballistic impact tests, corresponding to the greatest energy absorption with a ballistic performance index 78.3% higher than that of neat fabrics. The results show great potential for reducing the weight of containment casing.

35 citations

Journal ArticleDOI
TL;DR: A hierarchical multiscale framework has been developed to predict the impact response of 3D braided composites, in which a bridging model was employed as a bridge between micro- and macro- scale and the results show that the numerical results are agreed with the experiments well.

31 citations

Journal ArticleDOI
TL;DR: In this article, a yarn pullout and ballistic impact test was conducted on different types of Kevlar and neat Kevlar fabrics using titanium blade-like projectiles to evaluate their impact resistances in aero-engine containment applications.
Abstract: Shear thickening fluids (STFs) have been proven promising in enhancing the anti-impact performance of woven fabric, which can be incorporated into soft-wall containment casing in aero-engine applications. In the current study, STFs having distinct different shear thickening behaviors were investigated through yarn pull-out and ballistic impact tests to understand the relationship between the rheological behavior of STFs and their effect in enhancing impact resistance, which provide insight into the design of STF-treated soft-wall casing. Spherical SiO2 particles of diameters 100 and 650 nm were employed to prepare the STFs, which were referred to as a-system (100 nm particles) and b-system (650 nm particles). The rheological properties were investigated for two STF system series. The critical shear rate is 0.6–3.2 s−1 for a suspension system composed of 650 nm silica particles, whereas the critical shear rate is 169–627 s−1 for that of 100 nm particles. Kevlar fabrics were impregnated with STFs, and ballistic impact tests were conducted on different types of STF–Kevlar and neat Kevlar fabrics using titanium blade-like projectiles to evaluate their impact resistances in aero-engine containment applications. Energy absorption characteristics, deformation features, and damage patterns are analyzed. Impact test results show that the STF made of 100 nm SiO2 improved the anti-impact performance of the Kevlar fabric and increased the energy absorption up to 56.6%, whereas it decreased in the treatment by STFs made of 650 nm SiO2. The different trends of the two suspension systems are attributed to the specific value of shear rate with critical shear rate. The maximum deformation is estimated and compared with the pyramid deformation formed in the fabric. The STF–Kevlar fabrics under impact are more compact and act as an integrated structure compared with the loose structure of neat Kevlar fabrics. Owing to the increased interyarn friction action after the STF treatment, less yarn slippage occurred during the impact. For fabrics treated with the a-system STF, primary yarns were stretched and pulled out from the overlap structure of the woven fabric, forming perpendicular strip areas with failure modes involving unraveled yarns. The perforated damage of the b-system-STF-treated fabrics is concentrated at the area directly in contact with the blade projectile, in which a small amount of yarns fractured and pulled out.

30 citations

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TL;DR: In this paper, the research on high cycle fatigue (HCF) strength of TC11 titanium alloy after subjected to foreign object damage (FOD) was presented. And the results showed that the microscopic characteristics of damage area include smooth area, micro cracks, micro notches, shear bands and loss of material (LOM).

22 citations


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Journal ArticleDOI
TL;DR: In this article, the authors present a Web of Science Record created on 2013-02-27, modified on 2017-05-10 and used for EPFL-ARTICLE-184271.
Abstract: Reference EPFL-ARTICLE-184271doi:10.1016/j.compositesa.2012.08.001View record in Web of Science Record created on 2013-02-27, modified on 2017-05-10

359 citations

Journal Article
TL;DR: In this paper, multi-phase shear thickening fluid (STF) treated high performance fabrics have attracted much attention in the applications of body protection and in order to improve the contribution of STF treatments, the authors designed multiphase STF and investigated the stab resistance of fabrics impregnated with these novel fluids.

93 citations

Journal ArticleDOI
TL;DR: A critical review of available literature for the prediction of the behavior of laminated composites and sandwich structures under hygrothermal conditions is carried out and summarized under different categories namely: static, vibration, buckling, postbuckling and miscellaneous studies as mentioned in this paper.
Abstract: Extensive numerical results available in published articles reflect the importance of the effects of geometric parameters, material properties, end conditions, hygrothermal fields, etc. on the behavior of laminated composite and sandwich structures when exposed to environmental conditions. A critical review of available literature for the prediction of the behavior of laminated composites and sandwich structures under hygrothermal conditions is carried out and summarized under different categories namely: static, vibration, buckling, post-buckling and miscellaneous studies (transient, dynamic, impact studies). Each category is further discussed separately in details highlighting the important outcomes of the research. In addition to that, each category is again grouped on the basis of the type of theory used by different researchers in their work. The displacement fields, thermal fields and the method adopted in different papers are also summarized.

82 citations

Journal ArticleDOI
TL;DR: In this paper, a multi-scale simulation framework based on finite element method is developed to model the impact failure behavior of triaxially braided composite, and a new meso-macro homogenization approach is proposed to estimate effective properties of subcell components with consideration of geometry continuity effect.
Abstract: A multi-scale simulation framework based on finite element method is developed to model the impact failure behavior of triaxially braided composite. The model integrates micromechanical model, meso-mechanical model and macro subcell model for the purpose of determining effective properties of fiber tows, estimating effective properties of subcell components, and simulating impact failure behavior of a braided composite structure, respectively. The meso-mechanical model compares excellently with experiments for mechanical behavior of both single-layer and six-layer specimens under quasi-static loading conditions. A new meso-macro homogenization approach is proposed to estimate effective properties of subcell components with consideration of geometry continuity effect. The subcell model is validated against experiments and utilized to simulate the high-speed impact behavior of a composite panel. The results of the subcell impact model compare well with experimental failure phenomena. The presented multi-scale modeling approach demonstrates its feasibility for impact analysis and design of braided composite structures.

76 citations

Journal ArticleDOI
TL;DR: In this article, the performance of filament wound fiber reinforced polymer (FRP) composite pipes and their critical properties, such as burst, buckling, durability and corrosion were discussed for the better quality performance.

56 citations