Flyer impact experiments are performed through different techniques (gas gun, electrical drivers, laser). Each technique presents advantages but also some limitations such as flyer integrity, flatness or dimensions uncertainty. To overcome these issues, we proposed a new technique using laser direct irradiation and based on LASAT principle.\\ Aluminium flyers are accelerated from 0.5 to 4.3 km/s. Velocity measurements are performed with different diagnostics (line-VISAR, PDV, shadowgraphy). A predictive model for flyer velocity depending on laser intensity, and using Rankine-Hugoniot equations, is presented and is in good agreement with experimental measurement. Flyer flatness and debris ejection are investigated as well as flyer curve shapping is mentioned. Two hypervelocity impacts (3.2 - 3.8 km/s) are performed on porous graphite as exploratory work. Comparison with simulation results suggests that the current flyer technique may be used for impact studies.

Laser ablation propulsion and orbit cleaning are developing areas of research. The general aim of laser-based techniques applied to this field is to maximize the momentum transfer produced by a laser shot. This work presents results from ballistic pendulum experiments under vacuum on aluminum, copper, tin, gold, and porous graphite targets. The work has focused on the metrology of the laser experiments to ensure good stability over a wide range of laser parameters (laser intensity ranging from 4 GW/cm2 to 8.7 TW/cm2, pulse duration from 80 ps to 15 ns, and wavelengths of 528 or 1057 nm). The results presented compile data from three experimental campaigns spanning from 2018 to 2021 on two different laser platforms and using different pulse durations, energies, and wavelengths. The study is complemented by the simulation of the momentum from the mono-dimensional Lagrangian code ESTHER. The first part of this work gives a detailed description of the experimental setup used, the ESTHER code, and the treatment of the simulations. The second part focuses on the experimental results. The third part describes the simulation results and provides a comparison with the experimental data. The last part presents possible improvements for future work on the subject.

The impact response of Nickel-based superalloys is still poorly documented with respect to the industrial interest in these materials. Here, laser-driven shocks are used to study and compare the dynamic behavior of Rene 65 superalloy with different microstructures at very high strain rates in the order of 106 s-1. Rene 65 specimens studied here are either in cast and wrought or additively manufactured (laser powder bed fusion) and subjected to different heat treatment conditions. Time-resolved velocity measurements provide the yield strength (Hugoniot elastic limit) and spall strength (resistance to dynamic tension) of each variant. In addition, post-recovery characterization gives insight into the initiation and propagation of dynamic fracture, which are shown to depend on the different manufacturing routes and thermal histories.

We present a series of shock-wave measurements on aluminum based on the use of a simultaneous Photon Doppler Velocimetry (PDV) and triature velocity interferometer system for any reflector. Our dual setup can accurately measure shock velocities, especially in the low-speed range (<100 m s-1) and fast dynamics (<10 ns) where measurements are critical in terms of resolution and unfolding techniques. Especially, the direct comparison of both techniques at the same measurement point helps the physicist in determining coherent settings for the short time Fourier transform analysis of the PDV, providing increased reliability of the velocity measurement with a global resolution of few m s-1 in velocity and few ns FWHM in time. The advantages of such coupled velocimetry measurements are discussed, as well as new opportunities in dynamic materials science and applications.

We investigate the mechanical response of Zr(50)Cu(40)Al(10 )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 10(6)-10(7)s(-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 1.7x10(6)s(-1) to 2.7x10(7)s(-1) . This range of data correspond to strain rates of hypervelocity impacts of small debris (approximate to 0.1-1 mm) on space infrastructure shields. Moreover, we highlight a strong dependency of the spall strength with the strain rate starting from 2x10(6)s(-1) . Indeed, the spall strength increases from 2.6 GPa, close to its quasi-static tensile strength value, up to 13.6 GPa.

Laser-driven shock experiments were conducted at a synchrotron facility to investigate the dynamic response of polyurethane foam. These experiments were coupled to in situ x-ray imaging to radiograph foam deformations and to determine the propagation velocity of stress waves. To increase the amplitude and the duration of the pressure load generated by the laser–matter interaction, the front surface of the target was covered with a confining layer (water and BK7 glass). Preliminary calibration tests involving time-resolved velocity measurements were performed to calculate the ablation pressure on the front surface of foam samples. The calculated pressure loads were used as input data for hydrodynamic simulations, in which the foam is modeled using a homogeneous porous macroscopic model, and model predictions were compared with experimental results. A fair consistency was found for most experiments, while for the others, an overestimation of the applied pressure is suspected, likely due to a laser breakdown within the confining medium. Finally, post-shot x-ray tomography of the recovered samples showed permanent deformation of the foam, unlike what was observed under quasi-static compression, and revealed heavy damage in the vicinity of the loaded zone.

Dynamic characteristics of femtosecond laser-generated shockwaves are investigated in ambient air. The experiments are performed using a 360-fs pulsed laser at a wavelength of 1.03 µm, with laser intensities up to 5 × 1014 W/cm2 (corresponding to about five times the air breakdown intensity threshold). Plasma and shockwave generation and propagation are visualized using a time-resolved transmission microscope. The maximum propagation velocity is in the order of Mach 30. By implementing a simple theoretical model, we find an initial pressure loading in the GPa range and shockwave pressure dropping down to MPa following propagation over few micrometers away from focus.

Interaction of intense femtosecond laser pulses with transparent materials has been a topic of growing interest in the past decades [1] . Among others, two features are particularly attractive. First, unprecedented material processing quality can be achieved as very small amount of energy is sufficient to induce the desired modification. Second, owing to localization of the laser peak intensity and the threshold-dependent nonlinear interaction, three-dimensional processing of transparent materials becomes possible. Although a growing number of applications exist [2] , several limitations are present. As an example, there is an everlasting need to minimize the laser affected volume and thus avoid unwanted crack propagation or mechanical defect generation during in-bulk material processing.

An ultrafast x-ray powder diffraction setup for laser-driven dynamic compression has been developed at the LULI2000 laser facility. X-ray diffraction is performed in reflection geometry from a quasi-monochromatic laser-generated plasma x-ray source. In comparison to a transmission geometry setup, this configuration allows us to probe only a small portion of the compressed sample, as well as to shield the detectors against the x-rays generated by the laser-plasma interaction on the front side of the target. Thus, this new platform facilitates probing of spatially and temporarily uniform thermodynamic conditions and enables us to study samples of a large range of atomic numbers, thicknesses, and compression dynamics. As a proof-of-concept, we report direct structural measurements of the bcc-hcp transition both in shock and ramp-compressed polycrystalline iron with diffraction signals recorded between 2θ ∼ 30° and ∼150°. In parallel, the pressure and temperature history of probed samples is measured by rear-side visible diagnostics (velocimetry and pyrometry).

Ejecta production upon the breakout of a shock wave at a rough surface has been the subject of extensive research work for about six decades. For a few years, we have investigated how laser-driven shocks could provide original, complementary data on this issue, over specific ranges of very high loading pressures, very short pulse durations (ns-order), small dimensions (tens of mu m) and extremely high strain rates. Here, selected results are presented in two metals (Cu and Sn), with either single triangular grooves of controlled depths and sharp angles or periodic, quasi-sinusoidal perturbations of different amplitudes. Experimental data combine measurements of jet velocities, using both optical shadowgraphy and Photonic Doppler Velocimetry, with ultra-fast laser based X-ray radiography to estimate mass ejection. Results are briefly compared with the predictions of analytical models and data obtained by other teams from explosive-based experiments, at lower pressure and over much larger temporal and spatial scales. Thus, both interest and limitations of laser shocks for this particular field of shock physics are illustrated and discussed.

When a shock wave of several tens of GPa breaks out at a free surface, a material is ejected ahead of this surface. The amount and velocity of such ejecta depend on the breakout pressure, state of the released material (solid, liquid, or mixed), whether the shockwave is supported or unsupported, and the initial geometrical perturbation (or roughness) of the free surface. If surface defects consist of small grooves, pits, or scratches, material ejection occurs in the form of jets breaking up into tiny particles (so-called microjetting), with jet tip velocities up to several times higher than the free surface velocity. The laser-based experiments presented in this paper focus on microjetting in shock-melted tin with periodic surface perturbations. Several complementary diagnostics are combined to measure the velocity and mass of ejecta during the early stages of the jetting process. One relevant advancement is the use of ps-laser x-ray radiography to probe the density of the ejecta in distinct jets a few tens of μm-wide. The effects of the depth and wavelength of the initial perturbation are investigated in both linear and near-linear growth regimes. The results are compared with predictions derived from the Richtmyer–Meshkov Instability theory.

In the ongoing development of additive manufacturing, the range of materials obtained by such processes constantly grows and comes with specific architecture and microstructure. In this study, the high strain rate behaviour of light aluminum alloy AlSi10Mg obtained by Selective Laser Melting (SLM) has been investigated under laser shock loading and impact of thin, laser-accelerated flyer plates. Both elastic-plastic response and spall fracture have been analysed on the basis of time-resolved measurements of free surface velocity, transverse visualization of shock-induced fragmentation and post-recovery observations (microscopy and tomography). Comparing two microstructures inherited from two sets of SLM building parameters reveals the strong influence of porosity and defects (lacks of fusion) on the Hugoniot Elastic Limit and spall strength. On the other hand, these properties do not depend much on the building direction, although fracture surface morphology is shown to be largely affected by the melt pools boundaries.

Natural rubber (NR) is the most commonly used elastomer in the automotive industry thanks to its outstanding fatigue resistance. Strain-induced crystallization (SIC) is found to play a role of paramount importance in the great crack growth resistance of NR [1]. Typically, NR exhibits a lifetime reinforcement for non-relaxing loadings [2-3]. At the microscopic scale, fatigue striations were observed on the fracture surface of Diabolo samples tested in fatigue. They are the signature of SIC [2,4,5]. In order to provide additional information on the role of SIC in the fatigue crack growth resistance of NR, striations are investigated through post-mortem analysis after fatigue experiments using loading ranging from-0.25 to 0.25. No striation was observed in the case of tests performed at 90{\textdegree}C. This confirms that the formation of striation requires a certain crystallinity level in the material. At 23{\textdegree}C, two striation regimes were identified: small striation patches with different orientations (Regime 1) and zones with large and well-formed striations (Regime 2). Since fatigue striations are observed for all the loading ratios applied, they are therefore not the signature of the reinforcement. Nevertheless, increasing the minimum value of the strain amplified the striation phenomenon and the occurrence of Regime 2.

Since the use of energetic approaches for the prediction of the number at macro-crack initiation in elastomers, a special attention is paid on fatigue crack growth at the microscopic scale. In filled natural rubber, failure surfaces exhibit wrenchings and striations (Le Cam et al., Int J Fatigue 52:82–94, 2013). Both are assumed to be due to strain-induced crystallization (SIC). Only four studies address fatigue striations (Le Cam et al., Int J Fatigue 52:82–94, 2013; Le Cam and Toussaint, Macromolecules 43:4708–4714, 2010; Flamm et al., Int J Fatigue 33:1189–1198, 2011; Muñoz-Mejia, Dissertation, Université Claude Bernard, Lyon I, 2011), while they could provide information of importance to better understand how SIC enables natural rubber to resist the crack growth. As striations are similar to fringe patterns, this study aims at using a phase extraction algorithm from a single fringe pattern to analyse the striation morphology (Robin et al., Appl Opt 44:7261–7269, 2005; Takeda et al., J Opt Sot Am 72:156–160, 1982; Servin et al., Appl Opt 36(19):4540–4548, 1997; Robin et Valle, Appl Opt 43(22):4355–4361, 2004; Valle et al., Strain 46(2):175–183, 2008). This phase extraction methodology is split into three steps. The first one consists in extracting the wrapped phase without orientation. The second step is devoted to the determination of the fringe pattern orientation from a classic unwrapping algorithm. The third and last step consists in using an unwrapping algorithm (Zuo et al., Opt Lasers Eng 85:84–103, 2016; Menese et al., Appl Opt 44(7):1207–1215, 2005) and to compute the difference between the unwrapped phase processed and a plane in order to analyse the evolution of the striation morphology. This methodology has been applied to characterize the striation morphology observed at the failure surface of specimen tested under different fatigue loading conditions.

In this study, the dynamic behaviour of light aluminum alloy AlSi10Mg obtained by additive manufacturing was investigated under laser shock loading. Two types of AlSi10Mg specimens were obtained by Selective Laser Melting (SLM) with two sets of building parameters, leading to specific architecture and microstructure compared to classical manufacturing processes. Their dynamic response to laser driven shocks was investigated on the basis of time-resolved measurements of free surface velocity, transverse visualization of shock-induced fragmentation, and post-recovery observations by means of microscopy. The results reveal a significant influence of the building parameters and SLM-inherited defects on both yield strength and spall strength values, as well as a strong dependence of high rate fracture behaviour on building direction of the material, mainly governed by melt pools shape and dissymmetry, with a combination of "interpool" and "intrapool" fracture modes.