Influence of Lateral Constraints on Wave Propagation in Finite Granular Crystals

Abstract In the presented work, wave dynamics of 2D finite granular crystals of polyurethane cylinders under low-velocity impact loading was investigated to gain better understanding of the influence of lateral constraints. The deformation of the individual grains in the granular crystals during the impact loading was recorded by a high-speed camera and digital image correlation (DIC) was used to calculate high fidelity kinematic and strain fields in each grain. These grain-scale kinematic and strain fields were utilized for the computation of the intergranular forces at each contact using a granular element method (GEM) based mathematical framework. Since the polyurethane were viscoelastic in nature, the viscoelasticity constitutive law was implemented in the GEM framework and it was shown that linear elasticity using the strain rate-dependent coefficient of elasticity is sufficient to use instead of a viscoelastic framework. These particle-scale kinematic and strain field measurements in conjunction with the interparticle forces also provided some interesting insight into the directional dependence of the wave scattering and attenuation in finite granular crystals. The directional nature of the wave propagation resulted in strong wave reflection from the walls. It was also noteworthy that the two reflected waves from the two opposite sidewalls result in destructive interference. These lateral constraints at different depths leads to significant differences in wave attenuation characteristics and the finite granular crystals can be divided into two regions: upper region, with exponential wave decay rate, and lower region, with higher decay rate.

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The Impact Performance of Woven-Fabric Thermoplastic and Thermoset Composites Subjected to High-Velocity Soft- and Hard-Impact Loading

Applied Composite Materials ◽

10.1007/s10443-019-09786-2 ◽

2019 ◽

Vol 26 (5-6) ◽

pp. 1389-1410 ◽

Cited By ~ 8

Author(s):

Jun Liu ◽

Haibao Liu ◽

Cihan Kaboglu ◽

Xiangshao Kong ◽

Yuzhe Ding ◽

...

Keyword(s):

Carbon Fibre ◽

Impact Loading ◽

High Velocity ◽

Image Correlation ◽

Woven Fabric ◽

High Velocity Impact ◽

Velocity Impact ◽

Impact Performance ◽

The Impact ◽

Carbon Fibre Composites

Abstract The present paper investigates the impact performance of woven-fabric carbon-fibre composites based upon both thermoplastic- and thermoset-matrix polymers under high-velocity impact loading by conducting gas-gun experiments at impact velocities of up to 100 m.s−1. The carbon-fibre reinforced-polymers (CFRPs) are impacted using soft- (i.e. gelatine) and hard- (i.e. aluminium-alloy) projectiles to simulate either a soft bird-strike or a hard foreign-body impact (e.g. runway debris), respectively, on typical composites employed in civil aircraft. The out-of-plane displacements of the impacted composite specimen are obtained by means of a three-dimensional Digital Image Correlation (DIC) system for the soft-projectile impact on the composites and the extent of damage is assessed both visually and by using portable C-scan equipment. The perforation resistance and energy absorbing capability of the composites are also studied by performing high-velocity impact experiments using the hard-projectile and the resulting extent and type of damage are identified. In addition, a Finite Element (FE) model is also developed to investigate the interaction between the projectile and the composite target.

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The Effect of a Coupling Agent on the Impact Behaviour of Flax Fibre Composites

Journal of Engineering Materials and Technology ◽

10.1115/1.4050637 ◽

2021 ◽

pp. 1-17

Author(s):

Cihan Kaboglu ◽

Jun Liu ◽

Haibao Liu ◽

Pietro Russo ◽

Giorgio Simeoli ◽

...

Keyword(s):

Impact Loading ◽

Coupling Agent ◽

Testing Machine ◽

Natural Fibers ◽

Flax Fiber ◽

Image Correlation ◽

Impact Tests ◽

Out Of Plane ◽

Plane Displacement ◽

The Impact

Abstract The effects of a coupling agent on the behavior of flax fiber reinforced composites have been investigated by testing the specimens under both quasi-static indentation and high velocity impact loading. The specimens are manufactured embedding a commercial flax fiber fabric in a polypropylene (PP) matrix, neat and pre-modified with a maleic anhydride grafted PP, the latter acting as a coupling agent to enhance the interfacial adhesion. Quasi-static (QS) compressive tests were performed using a dynamometer testing machine equipped with a high-density polyethylene indenter having the same geometry of the projectile employed in the impact tests. The impact tests were conducted setting three different impact velocities. Digital Image Correlation maps of out-of-plane displacement were employed to compare the specimens with and without the coupling agent. The QS testing results indicate that the coupling agent has an enhancing influence on the bending stiffness of tested flax composites. The testing results show that the coupling agent improves the mechanical behavior by decreasing the out-of-plane displacement under impact loading. This approach gives rise to new materials potentially useful for applications where impact performance is desired whilst also providing an opportunity for the incorporation of natural fibers to produce a lightweight composite.

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Simulation of Seismic Wave Propagation on Asteroid Ryugu Induced by The Impact Experiment of The Hayabusa2 Mission: Limited Mass Transport by Low Yield Strength of Porous Regolith

Journal of Geophysical Research Planets ◽

10.1029/2020je006594 ◽

2020 ◽

Author(s):

G. Nishiyama ◽

T. Kawamura ◽

N. Namiki ◽

B. Fernando ◽

K. Leng ◽

...

Keyword(s):

Wave Propagation ◽

Yield Strength ◽

Mass Transport ◽

Seismic Wave ◽

Seismic Wave Propagation ◽

Impact Experiment ◽

Limited Mass ◽

The Impact

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The influence of internal structure on wave propagation in elastic beams under impact loading

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2000979 ◽

2000 ◽

Vol 10 (PR9) ◽

pp. Pr9-475-Pr9-480

Author(s):

E. I. Prockuratova ◽

C. Gearhar

Keyword(s):

Wave Propagation ◽

Internal Structure ◽

Impact Loading ◽

Elastic Beams

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Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽

10.3390/s21051602 ◽

2021 ◽

Vol 21 (5) ◽

pp. 1602

Author(s):

Ángel Molina-Viedma ◽

Elías López-Alba ◽

Luis Felipe-Sesé ◽

Francisco Díaz

Keyword(s):

Modal Analysis ◽

Energy Absorption ◽

High Speed ◽

Operational Modal Analysis ◽

Modal Identification ◽

Image Correlation ◽

Composite Panel ◽

Impact Excitation ◽

Full Field ◽

The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

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Strength Enhancement of Superduplex Stainless Steel Using Thermomechanical Processing

Metals ◽

10.3390/met11071094 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1094

Author(s):

M. A. Lakhdari ◽

F. Krajcarz ◽

J. D. Mithieux ◽

H. P. Van Landeghem ◽

M. Veron

Keyword(s):

Mechanical Properties ◽

Stainless Steel ◽

Thermomechanical Processing ◽

Tensile Tests ◽

Image Correlation ◽

Strength Enhancement ◽

Industrial Material ◽

Superduplex Stainless Steel ◽

The Impact ◽

Strength Improvement

The impact of microstructure evolution on mechanical properties in superduplex stainless steel UNS S32750 (EN 1.4410) was investigated. To this end, different thermomechanical treatments were carried out in order to obtain clearly distinct duplex microstructures. Optical microscopy and scanning electron microscopy, together with texture measurements, were used to characterize the morphology and the preferred orientations of ferrite and austenite in all microstructures. Additionally, the mechanical properties were assessed by tensile tests with digital image correlation. Phase morphology was not found to significantly affect the mechanical properties and neither were phase volume fractions within 13% of the 50/50 ratio. Austenite texture was the same combined Goss/Brass texture regardless of thermomechanical processing, while ferrite texture was mainly described by α-fiber orientations. Ferrite texture and average phase spacing were found to have a notable effect on mechanical properties. One of the original microstructures of superduplex stainless steel obtained here shows a strength improvement by the order of 120 MPa over the industrial material.

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Use of the AE Effect to Determine the Stresses State in AAC Masonry Walls under Compression

Materials ◽

10.3390/ma14133459 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3459

Author(s):

Radosław Jasiński ◽

Krzysztof Stebel ◽

Paweł Kielan

Keyword(s):

Ultrasonic Waves ◽

Image Correlation ◽

Masonry Walls ◽

Acceptable Error ◽

Compressive Stresses ◽

Deformation State ◽

Hydrostatic Stresses ◽

Stress States ◽

The Impact ◽

Masonry Units

Safety and reliability of constructions operated are predicted using the known mechanical properties of materials and geometry of cross-sections, and also the known internal forces. The extensometry technique (electro-resistant tensometers, wire gauges, sensor systems) is a common method applied under laboratory conditions to determine the deformation state of a material. The construction sector rarely uses ultrasonic extensometry with the acoustoelastic (AE) method which is based on the relation between the direction of ultrasonic waves and the direction of normal stresses. It is generally used to identify stress states of machine or vehicles parts, mainly made of steel, characterized by high homogeneity and a lack of inherent internal defects. The AE effect was detected in autoclaved aerated concrete (AAC), which is usually used in masonry units. The acoustoelastic effect was used in the tests described to identify the complex stress state in masonry walls (masonry units) made of AAC. At first, the relationships were determined for mean hydrostatic stresses P and mean compressive stresses σ3 with relation to velocities of the longitudinal ultrasonic wave cp. These stresses were used to determine stresses σ3. The discrete approach was used which consists in analyzing single masonry units. Changes in velocity of longitudinal waves were identified at a test stand to control the stress states of an element tested by the digital image correlation (DIC) technique. The analyses involved density and the impact of moisture content of AAC. Then, the method was verified on nine walls subjected to axial compression and the model was validated with the FEM micromodel. It was demonstrated that mean compressive stresses σ3 and hydrostatic stresses, which were determined for the masonry using the method considered, could be determined even up to ca. 75% of failure stresses at the acceptable error level of 15%. Stresses σ1 parallel to bed joints were calculated using the known mean hydrostatic stresses and mean compressive stresses σ3.

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