Numerical simulation of hypervelocity impact on CFRP/Al HC SP spacecraft structures causing penetration and fragment ejection

A representative carbon fiber reinforced plastic/aluminum honeycomb sandwich panel (CFRP/Al HC SP) spacecraft structure has been modeled in the hydrocode AUTODYN using the state-of-the-art ADAMMO material model [Riedel W, Harwick W, White D, Clegg R. Advanced material damage models for numerical simulation codes. ESA CR(P) 4397, 2003] to study the performance of the structure during impact events that cause perforation and fragment ejection. A new procedure combining a series of existing theoretical methods has been developed and applied to derive a full set of coarse material data. The data set has been implemented in AUTODYN, and the results of the numerical simulation have been compared to experimental impact test data. For impact tests performed near the structural ballistic limit, quantitatively accurate results were obtained over a range of impact velocities and angles. A further increase in the projectile size resulted in significant destruction of the sandwich panel front face-sheet and diversion from the experimental damage measurements. Inspection of the numerical model has shown non-localized propagation of inter-laminar delaminations, possibly caused by an under-prediction of the laminate dynamic inter-laminar tensile strength. The effects of the delamination propagation occur over an extended time scale and were not found to affect the state and trends of the fragment cloud ejected into the satellite interior. Accordingly, experimental trends of fragment cloud dispersion have been qualitatively reproduced.     

Shock properties of conventional and high strength concrete: Experimental and mesomechanical analysis

Large scale heterogeneity is a major problem when shock properties of concrete materials shall be derived efficiently. A mesomechanical method proposed earlier [Riedel W. Beton unter dynamischen Lasten: Meso- und makromechanische Modelle und ihre Parameter, Ed.: Fraunhofer-Institut für Kurzzeitdynamik, Ernst-Mach-Institut EMI. Freiburg/Brsg.: Fraunhofer IRB Verlag; 2004. p. 117–43. ISBN:3-8167-6340-5 〈http://www.irbdirekt.de/irbbuch/〉; Thoma K, Riedel W, Hiermaier S. Mesomechanical modeling of concrete shock response, experiments and linking to macromechanics by numerical analysis. In: Proceedings of European conference on computational mechanics, München, Germany, September 1999 (CD-ROM).], combining plate impact experiments on the constituents ‘cement’ and ‘aggregate’ together with simulations of the concrete mesostructure, is extended in this work. Hereby, the parameters describing macroscopic stress wave propagation are analysed in direct simulations of the discontinuous composite of aggregate, mortar and pores. This allows the replacement of an important number of experiments on large samples with inevitable scattering by a reduced set of smaller standard tests together with simulations. The basics and the validation of this methodology are demonstrated in the acoustic regime and compared to available shock experiments for a wide pressure range. The present paper describes the enlargement of the pressure range for the derived equation of state properties. Therefore, the concrete mortar has been impact tested in shock reverberation configuration leading to reflected pressures up to 18 GPa. The shock and equation of state properties are derived for two 35 MPa conventional strength mixtures and a 135 MPa high strength concrete. The results are compared to available literature sources.     

The effect of CFRP and CFRP/concrete interface models when modelling retrofitted RC beams with FEM

Concrete structures retrofitted with fibre reinforced plastic (FRP) applications have become widespread in the last decade due to the economic benefit from it. This paper presents a finite element analysis which is validated against laboratory tests of eight beams. All beams had the same rectangular cross-section geometry and were loaded under four point bending, but differed in the length of the carbon fibre reinforced plastic (CFRP) plate. The commercial numerical analysis tool Abaqus was used, and different material models were evaluated with respect to their ability to describe the behaviour of the beams. Linear elastic isotropic and orthotropic models were used for the CFRP and a perfect bond model and a cohesive bond model was used for the concrete–CFRP interface. A plastic damage model was used for the concrete. The analyses results show good agreement with the experimental data regarding load–displacement response, crack pattern and debonding failure mode when the cohesive bond model is used. The perfect bond model failed to capture the softening behaviour of the beams. There is no significant difference between the elastic isotropic and orthotropic models for the CFRP.     

Comparison study of MPM and SPH in modeling hypervelocity impact problems

Due to the high nonlinearities and extreme large deformation, the hypervelocity impact simulation is a challenging task for numerical methods. Meshfree particle methods, such as the smoothed particle hydrodynamics (SPH) and material point method (MPM), are promising for the simulation of hypervelocity impact problems. In this paper, the material point method is applied to the simulation of hypervelocity impact problems, and a three-dimensional MPM computer code, MPM3D, is developed. The Johnson–Cook material model and Mie–Grüneisen equation of state are implemented. Furthermore, the basic formulations of MPM are compared with SPH, and their performances are compared numerically by using MPM3D and LS-DYNA SPH module.     

Simulation of orbital debris impact on the Space Shuttle wing leading edge

A series of three dimensional hypervelocity impact simulations has been performed to study the effects of orbital debris impact on the Space Shuttle wing leading edge. The simulations employed an improved hybrid particle-finite element method and an orthotropic elastic-plastic material model recently developed for reinforced carbon–carbon. The simulation results are consistent with the available experimental data, and suggest the use of momentum scaling to estimate damage effects for impact conditions outside the range of current light gas gun technology. Projectile shape and orientation effects appear to be modest for flat plate projectiles at impact velocities above the ballistic limit.     

Characterizing the transient response of CFRP/Al HC spacecraft structures induced by space debris impact at hypervelocity

To quantify the disturbance induced by the impact of micrometeoroid and space debris particles at hypervelocity on vibration-sensitive CFRP/Al HC SP satellite platforms a method is presented which uses experimentally validated hydrocode models to characterize the impact-induced transient wave in the local structure. Key features of the transient waveform are simplified by a mathematical function which is expressed in terms of impactor momentum. Evolution of the transient waveform is characterized using multiple measurement gauges located on the sandwich panel facesheets outside the area of mechanical damage. The characterization is then used to extrapolate the elastic waveform back to the impact location. The elastic-equivalent excitation of a CFRP/Al HC SP is defined in terms of force with respect to time for application in finite element structural codes for propagation of the local disturbance to vibration-sensitive locations (i.e. measurement devices).     

Meso-scale modeling of hypervelocity impact damage in composite laminates

ObjectivesThis paper presents an approach to numerical modeling of hypervelocity impact on carbon fiber reinforced plastics (CFRP).MethodsThe approach is based on the detailed meso-scale representation of a composite laminate. Material models suitable for explicit modeling of laminate structure, including fiber-reinforced layers and resin-rich regions, are described. Two numerical impact tests with significantly different impact energies were conducted on thermoplastic AS4/PEEK materials with quasi-isotropic layups. Simulations employed both SPH and Finite element methods.ResultsResults of simulations are verified against experimental data available from the literature and demonstrate good correlation with the experiments.ConclusionsDeveloped modeling approach can be used in simulations where post-impact damage progression in composite material is of the main focus.     

Nomex Kevlar平纹织物超高速撞击本构模型开发

为了研究Nomex-Kevlar平纹织物对空间碎片的超高速撞击力学特性, 运用LS-DYNA本构模型二次开发技术开发了Nomex-Kevlar平纹织物在超高速撞击条件下的带最大应力失效标准的线弹性正交各向异性本构模型, 并定义了Nomex-Kevlar平纹织物在超高速撞击条件下的Gruneison状态方程参数。运用光滑粒子流体动力学方法和有限元方法建立了与NASA试验工况相同的Al-2017-T4球形弹丸以6.84km/s速度斜向30°撞击Nomex-Kevlar平纹织物的数值分析模型。仿真结果与试验结果的比较表明, 本文中开发的本构模型以及建立的数值分析模型可以准确描述Nomex-Kevlar平纹织物的超高速撞击力学特性。      

Analysis and simulation of hypervelocity gouging impacts for a high speed sled test

An analysis and simulation of the gouging impact phenomenon which occurs at the Holloman Air Force Base High Speed Test Track (HHSTT) during hypervelocity impact testing is presented. Simulations of the sled/rail interactions were conducted using the hydrocode, CTH. These simulations utilize the most accurate and validated material models for the sled shoes (VascoMax 300) and rail (1080 steel) – which were recently developed. Sled shoe impacts with the rail were evaluated using various geometries possible in the field. The conditions leading to hypervelocity gouging were identified, as well as the condition which resulted in rail wear. The CTH simulations match results observed in the field extremely well. Recommendations are made, based on the latest material models and simulations, which should significantly reduce the occurrences of hypervelocity gouging at the HHSTT.     

HVI tests on CFRP laminates at low temperature

The paper reports a result of low temperature hypervelocity impact (HVI) tests of aluminum sphere against a 16-ply quasi-isotropic Carbon Fiber Reinforced Plastic (CFRP) laminate plate at speed ranging from 1.4 to 5.4 km/s in air at 10 Pa. The result was compared with room temperature impacts. At low speed impact on CFRP plates, fracture patterns of specimens varied depending on their temperatures, whereas at high-speed impact, any significant differences in the fracture patterns around penetration holes and independent of the temperatures.     

High velocity impact characteristics of MWNT added CFRP at LEO space environment

In this paper, multi-wall carbon nanotube (MWNT) added carbon fiber reinforced plastics (CFRP) composites are suggested as solutions to improve the impact energy absorbing capability of CFRP for spacecraft application because it was proven that the resistance against LEO environment and the quasi-static material properties of CFRP can be improved by adding MWNT in previous papers. To verify the effect of MWNT on the impact energy absorbing capability of composite materials, normal CFRP and MWNT-reinforced CFRP were prepared and tested by using a two-stage light gas gun that can accelerate an aluminum ball of a diameter of 5.56 mm to 1 km/s. And the applicability of MWNT against hypervelocity impact of space debris was studied. In addition, accelerated ground simulation experiments were performed for each material model to simulate the aging of composite materials to verify the effect of LEO environmental aging on impact absorbing capability of composites. For the aging experiment, the impact specimens were simultaneously exposed to high vacuum, atomic oxygen, ultra violet light, and thermal cycling. After being exposed to simulated LEO environment, high velocity impact tests were performed for each material. As a result, MWNT did not have a significant improvement on the impact energy absorbing capability of CFRP under high velocity impact, even though the quasi static material properties are improved by adding MWNT. This is caused by the early generation of fiber breakages on the impact surface before enough generation of progressive failure which is one of the impact energy absorbing mechanism. Similarly, MWNT has less effect on the impact energy absorbing capability of CFRP under LEO environment.     

Effects of temperature on impact damages in CFRP composite laminates

In this paper, the effect of temperature variations (low and high temperatures) was studied experimentally on impact damage to CFRP laminates. The composite laminates used in this experiment were CF/EPOXY orthotropic laminated plates with lay-up [0₆/90₆]_s and [0₄/90₄]_s, and CF/PEEK orthotropic laminated plates with a lay-up of [0₆/90₆]_s. A steel ball launched by the air gun was used to generate the CFRP laminate impact damage. For impact-damaged specimens, nondestructive evaluation (NDE), such as a scanning acoustic microscopy (SAM) was performed on the delamination-damaged samples to characterize damage growth at different temperatures.

Therefore, this study was undertaken to experimentally determine the interrelations between impact energy and impact damage (i.e. the delamination area and matrix) of CFRP laminates (CF/EPOXY and CF/PEEK) subjected to foreign object damages (FOD) at low and high temperatures.     

Compression fatigue failure of CFRP laminates with impact damage

The objective of this study is to investigate failure mechanisms of impact-damaged CFRP laminates subjected to compression fatigue. Two kinds of composite materials, UT500/Epoxy and AS4/PEEK, were used to examine the dependence of failure behavior on the material properties such as interlaminar toughness. Impact-induced delaminations in the UT500/Epoxy specimen were considerably larger than those in the AS4/PEEK specimen. The S–N curves for the UT500/Epoxy specimens with impact damage exhibited a similar tendency to those without impact. The impact-induced delamination in the UT500/Epoxy specimen grew widthwise to the free edge on the rear side of the specimen during the fatigue test. On the other hand, the AS4/PEEK specimens without impact exhibited a more steeply declining S–N curve than those with impact damage. The delaminations in the impacted AS4/PEEK specimen did not reach the free edge before the fatigue fracture.     

On the response of two commercially-important CFRP structures to multiple ice impacts

Carbon-fibre reinforced composites (CFRPs) are likely to feature heavily as structural elements of future aerospace vehicles due to their high stiffness and low densities. However, such components are likely to be subjected to a variety of impact-related events during their in-service lives. One area which has only received limited attention in the literature is that of ice impact on CFRP structures; e.g. hail stone impacts on aerospace components. In this study the response of two aerospace-grade CFRP structures (one woven and one uni-directional lay-up) to multiple ice impacts with cumulative impact energies in the range 72–1215 J was investigated. Six empirical damage categories were identified, ranging from no apparent surface damage (Type 1) to penetration accompanied by complete lay-up disruption (Type 6). Surface damage was found to correlate with changes in recovered panel properties; determined by ultrasonic C-Scan and compression-after-impact strength tests. With both CFRP structures sub-surface disruption and residual compressive strength varied linearly with total impact energy; suggesting that damage in such structures is cumulative in nature. Further, in line with previous studies, the woven structure consistently exhibited lower levels of damage at a given impact energy, even when damage extent was normalised by areal density.     

Hypervelocity impact damage to composites

This paper presents the results of hypervelocity impact tests conducted on graphite/PEEK laminates. Both flat plate and circular cylinders were tested using aluminum spheres of varying size, travelling at velocities from 2–7 km/s. The experiments were conducted at several facilities using light gas guns. Normal and oblique angle impacts were investigated to determine the effect of impact angle, particle energy and laminate configuration on the material damage and ejecta plumes. Correlations were established between an energy parameter and the impact crater size, spallation damage and debris cone angle. Secondary damage resulting from the debris plume on adjacent composite structures was studied using high-speed photography and witness plates. It was observed that for hypervelocity impacts, the debris plume particles have sufficient energy to penetrate adjacent structures and cause major structural damage as well.     

A single energy-based parameter to assess protection capability of debris shields

Protecting spacecraft structures against hypervelocity impacts (HVIs) of space debris, which may cause fatal damage to the spacecraft structures, has received wide attention. In this paper, the numerical simulation of hypervelocity solid–solid impacts is conducted and an energy-based parameter to assess protection capability of debris shields is proposed. To numerically simulate the hypervelocity impact phenomena, a two-dimensional improved smoothed particle hydrodynamics (SPH) method with new particle generation and particle merger techniques is used. The spatial and temporal distributions of the kinetic energy flux density of a debris cloud at the position of the upper surface of a pressure wall are calculated, and the correlation between the kinetic energy of the debris cloud and the deformation and fracture behavior of the pressure wall is discussed. Finally, based on the maximum value of the total kinetic energy of debris cloud per unit area at the position of the upper surface of a pressure wall, an energy-based parameter to assess protection capability of debris shields is proposed.     

Simulations of hypervelocity impact damage and fracture of aluminum targets using a constitutive-microdamage material model

The material damage and fracture of Aluminum 1100 target plates that experience hypervelocity impact by glass projectiles traveling at 6 km/s are simulated using a proposed constitutive-microdamage material model. The model is best suited for polycrystalline metals that are subject to hypervelocity impact at the lower range of velocities. Simulations are performed for three projectile diameter-target thickness ratios that produce a wide range of damage features. The predicted damage is compared with that of the corresponding test laboratory specimens, illustrating the capability of the constitutive-microdamage model.