Hypervelocity Impact Conditions Research Articles

Projectile fragmentation and debris cloud formation behaviour of wavy plates in hypervelocity impact

Continuously increasing micro meteorite and orbital debris (MMOD) in space poses a threat to any manned or unmanned space vehicle with increasing probability of damaging object impact. To address the sufficient level of protection of space vessels, many Whipple shield configurations has been studied for over half a century. Bumper plate of Whipple shields studied in existing literature are flat surfaced plates. In contrast to earlier studies, this paper investigates the reaction of bumper plates with wavy surfaces against hypervelocity impact by analysing how they contribute to projectile fragmentation, formation of debris cloud, and how they dissipate the impact energy. Aluminium plates with four different surface wave profiles (WPs) were numerically investigated under hypervelocity impact conditions to assess their performance on disintegration of the impacting projectile. Fragmentation patterns of spherical aluminium projectile and debris cloud generated by projectile-wavy plate couples were examined and compared with the equivalents observed in flat-surfaced plate impact. A hybrid Smoothed Particle Hydrodynamics (SPH) combined with finite element modelling (FEM) approach was adopted using ANSYS software to simulate hypervelocity impact phenomenon at 3 km/s. Results of the numerical work carried out in this study revealed the distinctive debris cloud generation that has never been reported before in the existing literature. Furthermore, compared to the flat plate, wavy plates are found to be more effective in decreasing the impact energy.

Zr-based metallic glasses Hugoniot under laser shock compression and spall strength evolution with the strain rate (> 107 s-1)

We investigate the mechanical response of Zr50Cu40Al10 and Zr60Cu30Al10 metallic glasses under laser shock compression to reproduce hypervelocity impact conditions such as high longitudinal stresses and high strain rates in an unknown range of 106−107s−1. Hugoniot curves and strength parameters (spall strength and strain rate) are obtained from free surface velocity profiles and compared with previous studies on the mechanical behaviour of Zr-based metallic glasses under plate impact experiments. We established Hugoniot curves for both compositions up to 100 GPa, corresponding to a particle velocity of 1.8 km/s, and consistent with literature up to 75 GPa. Concerning the strength parameters, we studied the evolution of the spall strength with the strain rate and obtained data unreached up to now from 1.7×106s−1 to 2.7×107s−1. This range of data correspond to strain rates of hypervelocity impacts of small debris (≈0.1−1mm) on space infrastructure shields. Moreover, we highlight a strong dependency of the spall strength with the strain rate starting from 2×106s−1. Indeed, the spall strength increases from 2.6 GPa, close to its quasi-static tensile strength value, up to 13.6 GPa.

Hypervelocity impact testing of a pressurized composite overwrapped pressure vessel and comparison to numerical analysis

As the outlook for space exploration becomes more ambitious and spacecraft travel deeper into space, it is increasingly important that systems with energetic material storage perform reliably within the space environment. Because hardware mass is limited, the use of high strength-to-weight Composite Overwrap Pressure Vessels (COPV) has enabled designers to store energy at a reduced mass penalty; however, because the composite overwrap carries a high fraction of the stress of pressurization, there is significant concern that damage to the composite overwrap can lead to vessel failure and potentially cause loss-of-vehicle/loss-of-crew. One of the greatest external threats to the integrity of a spacecraft’s COPV is an impact from the meteoroid and orbital debris environments (MMOD). Because the limited research regarding this problem cannot be generalized, the capacity for these vessels to tolerate such impacts is not well understood. This report details some of the early experimental efforts undertaken by the Hypervelocity Impact Technology (HVIT) group in the support of a NASA Engineering and Safety Center (NESC) assessment to understand how hypervelocity impact conditions comparable to MMOD impacts initiate catastrophic COPV failure. In addition to this experimental work, this publication also reports on the development of a numerical method to guide the interpretation of the experimental data and extension to other flight relevant configurations.

FTMP-BASED SIMULATION OF TWIN NUCLEATION AND SUBSTRUCTURE EVOLUTION UNDER HYPERVELOCITY IMPACT

The deformation twinning model based on Field Theory of Multiscale Plasticity (FTMP) represents the twin degrees of freedom with the incompatibility tensor, which is incorporated into the hardening law of the FTMP-based crystalline plasticity framework. The model is further implemented into a finite element code. In the present study, the model is adapted to a single slip-oriented FCC single crystal sample, and preliminary simulations are conducted under static conditions to confirm the model's basic capabilities. The simulation results exhibit nucleation and growth of twinned regions, accompanied by serrated stress response and overall softening. Simulations under hypervelocity impact conditions are also conducted to investigate the model's descriptive capabilities of induced complex substructures composing of both twins and dislocations. The simulated nucleation of twins is examined in detail by using duality diagrams in terms of the flow-evolutionary hypothesis.

The Self-Healing Capability of Carbon Fibre Composite Structures Subjected to Hypervelocity Impacts Simulating Orbital Space Debris

The presence in the space of micrometeoroids and orbital debris, particularly in the lower earth orbit, presents a continuous hazard to orbiting satellites, spacecrafts, and the international space station. Space debris includes all nonfunctional, man-made objects and fragments. As the population of debris continues to grow, the probability of collisions that could lead to potential damage will consequently increase. This work addresses a short review of the space debris “challenge” and reports on our recent results obtained on the application of self-healing composite materials on impacted composite structures used in space. Self healing materials were blends of microcapsules containing mainly various combinations of a 5-ethylidene-2-norbornene (5E2N) and dicyclopentadiene (DCPD) monomers, reacted with ruthenium Grubbs' catalyst. The self healing materials were then mixed with a resin epoxy and single-walled carbon nanotubes (SWNTs) using vacuum centrifuging technique. The obtained nanocomposites were infused into the layers of woven carbon fibers reinforced polymer (CFRP). The CFRP specimens were then subjected to hypervelocity impact conditions—prevailing in the space environment—using a home-made implosion-driven hypervelocity launcher. The different self-healing capabilities were determined and the SWNT contribution was discussed with respect to the experimental parameters.

Characteristics of Shock Initiation of Single-Shell and Double-Shell Casing Charges

According to different type tactical missile warhead, structure of which was equivalent to charges covered by single-shell or double-shell. The shock initiation response of cast TNT charges, covered by single-shell and double-shell casing impacted by hypervelocity fragment was investigated using non-linear dynamics software AUTODYN. Results shows that in hypervelocity impact conditions, the first layer of double-shell charge imposed severe breaking effect to fragment and generated debris clouds, then the surface impulse density of fragment to rear shell reduces significantly. When impacted by same mass, shape, velocity projectile, deflagration will occur for single shell charges, however, no deflagration can be observed for double shell charges with the same thickness.

Predicting fracture and fragmentation in ceramic using a thermo-mechanical basis

In this paper, the corrective smoothed particle method (CSPM) numerical algorithm as a modification of traditional SPH particle method has been employed to predict fracture and fragmentation in ceramics using a thermo-mechanical basis under hypervelocity impact conditions. In order to study the brittle behavior in ceramic, the JHB computational constitutive model which considers phase transition in a solid continuum has been applied. An appropriate heat conduction equation has been coupled with the Johnson–Cook yield criteria in order to get more accurate temperature field especially in impact zone which consequently gives a more exact solution in such problems coming with highly produced magnitude of pressure and temperature in the material. It has been shown that implementation of the CSPM scheme with a thermo-mechanical basis can predict the brittle fracture and fragmentation in ceramics under hyper velocity impact conditions.

Automated design of threats and shields under hypervelocity impacts by using successive optimization methodology

In this study, predictive hydrocode simulations are coupled with approximate optimization (AO) methodology to achieve successive design automation for a projectile-Whipple shield (WS) system at hypervelocity impact (HVI) conditions. Successive design methodology is first applied to find the most dangerous threat for a given WS design by varying the shape and orientation of a projectile while imposing constraints on the total projectile mass and radar cross section (RCS). Subsequent optimization procedure is then carried on to improve the baseline WS design parameters. A parametric multi-layered stuffed WS model is considered with varying thicknesses of each layer and variable positions of the inter-layers while having a constraint on the areal density. HVI simulations are conducted by using a non-linear explicit dynamics numerical solver, LS-DYNA. Coupled finite element and smoothed particle hydrodynamics (SPH) parametric models are developed for the predictive numerical simulations. LS-OPT is employed to implement the design optimization process based on response surface methodology. It is found that the ideal spherical projectiles are not necessarily presenting the most dangerous threat compared to the ones with irregular shapes and random orientations, which have the same mass and RCS. Therefore, projectiles with different shapes and orientations should be considered while designing a WS. It is also shown that, successive AO methodology coupled with predictive hydrocode simulations can easily be utilized to enhance WS design.

Molecular Dynamics Study of Impact Angle Dependence of Structure of Debris Cloud under Hyper Velocity Impact

A molecular dynamics simulation is carried out to study the fractureunder hyper-velocity impact conditions when a space debris attack to aman-made satellite. In this paper, oblique-impact simulations areperformed since most orbital debris impacts are oblique in the realcondition. Aluminum projectile impacts aluminum target at 0−, 30−, and 45−degrees obliquity. Impact velocity is 8km/s, and target thickness-projectile diameter ratio t/D is 0.684. As the angle of obliquity isincreasing, the velocity of debris after impact is decreasing, whilethe deviation of the line of flight is increasing. These resultsqualitatively agrees well with experimental results.

Hypervelocity impact damage prediction in composites: Part II—experimental investigations and simulations

The extension of damage in composites during hypervelocity impact (HVI) of space debris is controlled by failure thresholds and subsequent energy consumption during damage growth. Characterisation and modelling of the material under partially and fully damaged states is essential for the prediction of HVI effects on fibre-composite structures. Improved experimental and numerical analysis techniques have been developed and are summarised in an accompanying paper. The present paper deals with the establishment of two precise damage experiments under HVI conditions as a validation basis for numerical simulations: The first type consists of space debris impact configurations optimised for damage evaluation and the second experiments reproduce HVI strain rates and compressions in plate impact. Coupling of damage analysis techniques (visual, ultrasonic, residual strength) to quantify different aspects of failure has been achieved. Numerical simulations using the commercial hydrocode AUTODYN in mesh-based and SPH formulations are presented using the material model and data described in the accompanying paper.

Advanced numerical models and material characterisation techniques for composite materials subject to impact and shock wave loading

The development and validation of an advanced material model for orthotropic materials, such as fibre reinforced composites, is described. The model is specifically designed to facilitate the numerical simulation of impact and shock wave propagation through orthotropic materials and the prediction of subsequent material damage. Initial development of the model concentrated on correctly representing shock wave propagation in composite materials under high and hypervelocity impact conditions [1]. This work has now been extended to further concentrate on the development of improved numerical models and material characterisation techniques for the prediction of damage, including residual strength, in fibre reinforced composite materials. The work is focussed on Kevlar-epoxy however materials such as CFRP are also being considered. The paper describes our most recent activities in relation to the implementation of advanced material modelling options in this area. These enable refined non-linear directional characteristics of composite materials to be modelled, in addition to the correct thermodynamic response under shock wave loading. The numerical work is backed by an extensive experimental programme covering a wide range of static and dynamic tests to facilitate derivation of model input data and to validate the predicted material response. Finally, the capability of the developing composite material model is discussed in relation to a hypervelocity impact problem.

Hypervelocity impact research - acceleration technology and applications -

Modern acceleration techniques like two- and three stage light gas guns, electrostatic and plasma accelerators, shaped charge launchers etc. will be reviewed and discussed with respect to their projectile mass and velocity ranges and their applicability for the experimental simulation of hypervelocity collisions. Recent studies in the fields of micrometeoroid/debris shielding (e.g. COLUMBUS Orbital Facility), as well as pressure vessel behavior under hypervelocity impact conditions will be presented as examples of applications.

Material response at hypervelocity impact conditions using laser induced shock waves

Dynamic fracture at hypervelocity impact conditions was investigated in different materials using short pulsed laser induced shock waves. All stages of damage evolution were identified for one dimensional or spherical shock wave impact geometry. A new experimental method is presented to estimate the shock pressure decay in materials. In the theoretical section we obtain the damage induced in the target, as follows: The shock wave is modeled by an expanding stress front, which creates micro-damage in the laser impacted layer and extrudes a bulge at the far surface. The calculated bulge geometry compares well with that observed by us for metal-adhesive-metal sandwiches. The micro-defects coalesce into macro- damage or fracture by a mechanism which is described by percolation theory.

Fracture modes in alumina at hypervelocity impact conditions

Experiments were performed to find the fracture patterns of alumina at hypervelocity impact conditions using short pulsed laser induced shock waves. For planar shock waves spalling was obtained, while using spherical shock waves, the samples developed Herzian (conical) fracture mode.

Disintegration behavior of metal rods subjected to hypervelocity impact

The disintegration behavior of projectile rods when impacting plates at velocities above 10 km/s is largely unexplored. Possible material responses include vaporization, melting, solid state phase changes, plastic flow, shear localization, and ductile and brittle tensile fracture. Two primary difficulties have prevented experimental studies of projectile response in this velocity regime, namely the lack of a technique for accelerating a projectile to velocities above 10 km/s, and the lack of a procedure for recovering the projectile remains after impact for examination. These difficulties were overcome recently by using an exploding foil technique to drive an impactor plate and by using a reverse ballistics test arrangement to allow projectile recovery. This paper describes this experimental procedure for investigating the disintegration behavior of projectile rods under hypervelocity impact conditions, presents preliminary results for steel, aluminum and lead, and discusses requirements for computational material response models.

Mechanics of high speed impact at normal incidence between plasticine long rods and plates

A brief literature review of long rod impact is given. Experimental results and observations on the penetration and perforation of plasticine targets of finite thickness (25 and 50 mm) impinged upon normally by long rods of plasticine of various length-to-diameter ratios (2–12) are presented and discussed. An account of the range of modes of deformation as it pertains to long rods and targets of identical materials is given, i.e. mushrooming of the projectile leading-end, partial penetration and embedment of the projectile in the target, gross target penetration by the projectile, and penetration followed by perforation. The difference in penetration behaviour as between long and short rods is discussed. Plasticine has been used for both the target and projectile materials in order to simulate hypervelocity impact conditions for deformable long rod projectiles on deformable target plates. This permits the use of equipment based on an industrial stud driver which is substantially cheaper than the equipment (e.g. a light gas gun) required to achieve the range of speeds necessary for hypervelocity conditions with real ballistics-related metals and alloys. Projectile-target interactions and damage observed in the present tests compare well with those reported in similar investigations using metallic projectiles and targets. The attraction of performing ballistics experiments with plasticine models outweighs such inherent limitations as the inability to model the extreme conditions of temperature and strain-hardening in real materials, because testing is cheap and easily performed in a laboratory.