Scholarly article on topic 'Response of a Aluminum Honeycomb Subjected to Hypervelocity Impacts'

Response of a Aluminum Honeycomb Subjected to Hypervelocity Impacts Academic research paper on "Materials engineering"

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{"Orbital Debris" / "Hydrocode AUTODYN" / "Two-Stage Light Gas Gun" / "Numerical simulation" / "space craft"}

Abstract of research paper on Materials engineering, author of scientific article — Kumi Nitta, Masumi Higashide, Yukito Kitazawa, Atushi Takeba, Masahide Katayama, et al.

Abstract We investigated the effect of hypervelocity impacts of micrometeoroids and small-scale orbital space debris (M/OD) on space structures by comparing numerical simulation results obtained using the AUTODYN-2D hydrocode with the results of experiments using a two- stage light gas gun. The response of an aluminum honeycomb structure to 6km/s high-velocity impacts is shown and discussed. AUTODYN-2D, which is used for impact analysis of complex physical systems including fluid and solid materials, was used to simulate impacts at 2–15km/s. Material models used in the simulation to allow investigation of phenomena over a wide range of impact velocities, including shock-induced vaporization, are also presented and discussed.

Academic research paper on topic "Response of a Aluminum Honeycomb Subjected to Hypervelocity Impacts"

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SciVerse ScienceDirect Procedía

Engineering

Procedía Engineering 58 (2013) 709 - 714 =

www.elsevier.com/locate/procedia

The 12th Hypervelocity Impact Symposium

Response of a Aluminum Honeycomb Subjected to Hypervelocity

Impacts

Kumi Nittaa*, Masumi Higashidea, Yukito Kitazawabc, Atushi Takebad, Masahide Katayamad, Haruhisa Matsumotob

aAerospace Research and Development Directorate, Japan Aerospace Exploration Agency, Chofu, Tokyo, Japan bAerospace Research and Development Directorate, Japan Aerospace Exploration Agency, Tsukuba, Ibaraki, Japan cAerospace Research and Development Aero-aEngine & Space Operations, IHI Corporation, , Koto-ku, Tokyo, Japan dScience and Engineering Systems Division, ITOCHU Techno-Solutions, Tokyo, Japan

Abstract

We investigated the effect of hypervelocity impacts of micrometeoroids and small-scale orbital space debris (M/OD) on space structures by comparing numerical simulation results obtained using the AUTODYN-2D hydrocode with the results of experiments using a two-stage light gas gun. The response of an aluminum honeycomb structure to 6 km/s high-velocity impacts is shown and discussed. AUTODYN-2D, which is used for impact analysis of complex physical systems including fluid and solid materials, was used to simulate impacts at 2-15 km/s. Material models used in the simulation to allow investigation of phenomena over a wide range of impact velocities, including shock-induced vaporization, are also presented and discussed. © 2012 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of the Hypervelocity Impact Society

Keywords: Orbital Debris, Hydrocode AUTODYN, Two-Stage Light Gas Gun, Numerical simulation, space craft

Nomenclature

ue Impact velocity (km/s)

t_thickness of plate (mm)_

1. Introduction

We have been conducting hypervelocity impact tests and numerical simulations in order to develop a Japanese spacecraft design guideline for the protection of satellites from a certain degree of M/OD impacts [1]. A working group was formed by members of JAXA, spacecraft manufacturers, experts and researchers in the field of hypervelocity impacts to investigate the effects of M/OD impacts on satellite critical parts and bumpers by hypervelocity impact (HVI) tests and analysis. The knowledge acquired is now being reflected in the spacecraft design guidelines.

As part of this effort, we investigated the response of an aluminum honeycomb panel to high-velocity impacts and compared the results of numerical simulations with impact tests.

* Corresponding author. Tel.: 81-50-3362-7996; fax: +0-000-000-0000 . E-mail address: nitta.kumi@jaxa.jp.

ELSEVIER

1877-7058 © 2013 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of the Hypervelocity Impact Society

doi: 10.1016/j.proeng.2013.05.082

2. Numerical analysis method — material model

2.1. Hydrocode

Numerical simulations were performed using the ANSYS AUTODYN hydrocode. As in almost all hydrocodes, the material model in ANSYS AUTODYN consists of three parts: i) an equation of state (E.O.S.) describing the relationships between pressure, density and internal energy (not temperature), ii) a material strength model that expresses constitutive relations of solid materials, and iii) a failure or fracture model. While a failure model for solid materials is typically used, it can also incorporates spalling (fracture by negative pressure) of liquid materials. In spite of their name, therefore, hydrocodes are formulated to simulate the highly dynamic and non-linear behavior of materials not only in liquid phase but also in solid and gas phases, and sometimes even the plasma state can be simulated approximately by use of an appropriate E.O.S.

2.2. Projectiles

Orbital space debris is composed of artificial objects which have been created through human space activities in near-Earth space since the launch of Sputnik I. The average density of space debris is considered to be 2.8-4.7 g/cm3 for objects smaller than 10 mm, while the relative impact velocity of orbital space debris in low earth orbit (LEO) is theoretically limited to approximately 16 km/s. In this assessment the space debris material is assumed to be aluminum alloy, SS304 or alumina. The propellant used in solid rocket motors (SRM) contains about 18% aluminum by weight, and these motors eject alumina particles from (xm-order dust up to cm-order slugs into earth orbit.

In our study, the Johnson-Holuquist II model [3] is adapted to simulate alumina. The material model includes an equation of state ("pressure"), a constitutive ("strength") model and a fracture or failure ("damage") model. The Steinberg-Guinan strength model [4] was applied to stainless steels when we compared and discussed the simulation results with corresponding experiments.

2.3. Targets

The targets tested and simulated numerically in this assessment are aluminum honeycomb panels (5056 aluminum core of 25.4 mm thickness). The Tillotson equation of state [5] was applied to materials that would be subjected to extremely severe physical conditions, because it takes into account shock-induced vaporization. The Steinberg-Guinan strength model [4] was applied to ductile materials: aluminum alloys in case of projectile velocities under 10 km/s.

Fig. 1. Two-stage light-gas gun at ISAS/JAXA

3. Experimental facilities

A series of experiments were carried out using a two-stage light-gas gun installed at ISAS/JAXA, shown in Fig. 1. This gas gun can accelerate a 0.2 g spherical projectile up to 7 km/s. The projectiles impact a target in a test chamber evacuated to a pressure of around 0.1 Pa. The spherical projectile is initially covered with a cylindrical polycarbonate sabot with a diameter of 7.1 mm and a length of 10.5 mm which guides the spherical projectile in the helium driving gas during acceleration and detaches from the projectile after sufficient velocity is attained.

The simulation results are compared with corresponding test results and discussed from the viewpoint of protection assessment of satellites from M/OD hypervelocity impacts. The material models in the numerical simulation used to enable the assessment of phenomena corresponding to a wide range of impact velocities, including shock-induced vaporization, are also discussed. To simulate M/ODs, we used spherical alumina projectiles with diameters ranging from 0.1 mm to 1 mm, with impact velocities of 2—15 km/s.

4. Results and Discussion

4.1. Experimental and Computational configuration

We developed two-dimensional axial symmetry analytical models. Projectiles impact a target of aluminum honeycomb sandwich typically used in the construction of satellite skin panels. The projectiles are assumed to be spherical with a diameter of (p0.3 mm, and have the properties of SUS304 stainless steel to simulate the kinetic energy of 6 km/s velocity impacts. Projectiles are modeled on the Lagrange solver.

The target is modeled as a disc of sufficient size. The target is an aluminium honeycomb core composed of 6.35 mm (1/4 inch) high cells arranged in a regular hexagonal grid, as shown in Fig. 2, sandwiched between aluminium skin sheets. In the numerical study, each cell is modeled as a circle bounded by the corresponding hexagon, as shown in the figure. Figure 3 shows the relationship between skin sheet thickness and projectile diameter. This numerical model requires a large computational effort because the skin sheet thickness is much smaller than the height of the honeycomb core.

aluminum honeycomb skin aluminum honeycomb skin

0.254 mm 0.254 mm

aluminum honeycomb core foil 0.0178 mm

projectile alumina ip 0.1 ~ !.0mm

2~ 15 km/s

6.35 mm

25.4 mm

Fig. 2. Two-dimensional axial symmetry analytical mode

Diameter of projectile 1.0mm Diameter of projectile 0.2mm

Numerical model of honeycomb corc

Fig. 3. Numerical model of honeycomb core

The accuracy of the numerical simulation was validated by comparison of the computed results with gas gun experiments. Figure 4 shows an image of the experimental set-up and Fig. 5 shows experimental results. Figure 6 depicts the numerical results that simulate the test case shown in Fig. 4. The particle diameter was 0.3 mm and the particle velocity was 6 km/s. Figure 6 shows the the damage at 50 ^s, which is the end time. In both cases the projectile penetrated the second (interior)

Fig. 4. Image of the experimental set-up [6]

Fig. 6. Deformation diagram of Calculation results and fragment phenomena at 50 ^s, impact velocity is 6 km/s

4.2. Hypervelocity Impact Results

We investigated the hypervelocity impact of space debris (M/OD) at 2-15 km/s by numerical simulation. The material models used in the simulation to cover a wide range of impact velocities were investigated and are discussed below. M/OD were simulated by alumina projectiles between 0.1 mm and 1 mm diameter.

Before presenting the results of our parametric study, we discuss the effect of the honeycomb core. In case of no honeycomb core, after a particle penetrates for first (exterior) skin there is a great expansion of fragments over a wide area, which consequently reduces the damage to the second (interior) skin (Fig. 7). With a honeycomb core between the skins, however, the honeycomb cell walls serve to contain the expansion so that the fragments are concentrated onto a small area of the second skin (Fig. 8). Our simulations confirm that the honeycomb core thus increases the damage to the inner skin.

The ballistic limit of the aluminum honeycomb panel is shown in Fig. 9. NO GO, Threshold and GO show a not penetrating to the second skin, borderline score to penetrate and a penetrating to the second skin, respectively. As the impact velocity increases, the ballistic limit of the aluminum honeycomb sandwich panel become progressively smaller. This behavior differs from the ballistic limit curve of a Whipple shield. The ballistic limit of the aluminum honeycomb sandwich panel has a flexion point at an impact velocity of approximately 10km/s.

We also compared with a case of aluminum honeycomb sandwich panel and aluminum plate which has same total thickness. Those results are quite similar and the curves are almost the same at over 10 km/s impact velocity. Our comparison shows that the aluminum honeycomb core negates the beneficial "bumper" effect of twin skins.

Fig. 7. Calculation results and fragment phenomena in case of no honeycomb core

Fig. 8. Calculation results and fragment phenomena in case of with a honeycomb core

Fig. 9. Summarizes the numerical simulation results

5. Summary

To assess the structural integrity of spacecraft subjected to the threat of hypervelocity impact by space debris, a numerical method was proposed mainly from the viewpoint of a material model suitable for extremely severe physical conditions: high pressure, temperature, strain, and strain rate, sometimes accompanied by shock-induced vaporization.

The results of numerical simulations adopting these material models were compared with hypervelocity impact tests using a two-stage light-gas gun, and examples of the impacts on an aluminum honeycomb panel were shown. Although only the results using the Lagragian method were discussed in this paper because of limitations of space, it has been demonstrated that the numerical analysis is able to effectively simulate the overall corresponding impact test results.

We showed the analysis of the response an aluminum honeycomb sandwich panel to hypervelocity impacts from 2 km/s to 15 km/s. We also verified that the ballistic limit of an aluminum honeycomb panel becomes progressively smaller as impact velocity increases. This differs from the ballistic limit of a Whipple shield. In future we will continue to extend the experimental and numerical investigations to a wider range of conditions in order to complete guidelines for the protection of unmanned spacecraft from space debris and micrometeoroid impacts.

Acknowledgements

The experiments were conducted and supported by the Space Plasma Laboratory, ISAS, and JAXA. This research was also supported by the JAXA design guideline Working Group 3.

References

[1] JAXA: Space Debris Protection Design Manual, JERG-2-144-HB001, 2009

[2] Integrity assessment of the spacecraft subjected to the hypervelocity impact by ceramic and metal projectiles simulating space debris and

micrometeoroids. Materials Science and Engineering B 173 (2010) pp. 148-154.

[3] G.R. Johnson, T.J. Holmquist, in: S.C. Schmidt, al. et (Eds.), Proceedings of theHigh-Pressure Science and Technology-1993 AIP Conf. Proc. No. 309,

AIP, New York (1994) pp. 981 - 984

[4] D.J. Steinberg, S.G. Cochran, M.W. Guinan: A constitutive model for metals applicable at high-strain rate, J. Appl. Phys. 51 (1980) pp.1498-1504.

[5] J.H. Tillotson: Metallic equations of state for hypervelocity impact. GA-3216, General Atomic, CA, July 1962.

[6] M. Higashide, N. Onose and S. Hasegawa : Evaluation of Space Debris Impact on Spacecraft Panels, 2011-r-28,ISTS28th,2011