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Evaluating the bonding quality of composite material is becoming one of the main challenges faced by aeronautic industries. This work aims to the development of a technique using shock wave, which would enable to quantify the bonding mechanical quality. Laser shock experiments were carried out. This technique enables high tensile stress generation in the thickness of composite bonds. The resulting damage has been quantified using different methods such as confocal microscopy, ultrasound and cross section observation. The discrimination between a correct bond and a weak bond was possible thanks to these experiments. Nevertheless, laser sources are not well adapted for optimization of such a test because of often fixed settings. That is why mechanical impacts on bonded composites were also performed in this work. By changing the thickness of aluminum projectiles, the generated tensile stresses by the shock wave propagation were moved toward the composite/bond interface. The made observations prove that the technique optimization is possible. The key parameters for the development of a bonding test using shock waves have been identified.

This paper deals with hemp-fibre and glass-fibre woven fabric/epoxy composites. The aim is to analyse damage mechanisms in these composites by comparing three different methods: acoustic emission, microscopic observations and stiffness loss measurement. For acoustic emission (AE), an experimental multi-scale analysis was developed in order to identify the different damage mechanisms. Tensile tests were performed on single yarn, neat epoxy resin and composite materials to determine their AE amplitude signatures. A statistical analysis of AE amplitude signals was realised and correlated with microscopic observations. This study has enabled to identify the amplitude and to track, during tensile tests, three types of damage in these composites: matrix cracking, interfacial debonding and reinforcement fracture. It shows the different processes of damage development in natural fibre reinforced composites, in comparison with glass fibre composites. These results were compared to the measured stiffness loss of composites. It allows one to highlight the difficulty to link this mechanical damage parameter with physical AE events.

Purpose – The purpose of this paper is to develop a laser shock adhesion test (LASAT) and evaluate its ability to reveal various bond qualities of stuck carbon fiber reinforced polymer (CFRP) industrial assemblies. Design/methodology/approach – Four grades of adhesion were prepared by release agent contamination of CFRP prior to assembly. Laser shots were performed at different intensities on these samples. Findings – To characterize and quantify the damage created by the propagation of shock waves in the bonded material, several diagnoses were used (confocal microscopy, ultra-sound inspection and cross-sections microscopy). These three post-mortem techniques are complementary and provide consistent results. Originality/value – The combination of these diagnoses along with the LASAT technique provides relevant information on the bond quality in agreement with GIC values measured by the University of Patras.

This paper presents the strain field analysis of a woven hemp composite. Two different stacking sequences were tested: [0/90] 7 and [±45] 7 . Tensile tests were coupled with a digital image correlation method in order to measure in-plane longitudinal, transverse and shear strain fields. Strong heterogeneities were observed in both stacking sequences. The obtained spatial resolution was fine enough to allow the comparison of maximum and minimum deformation areas in strain fields with the corresponding weave architecture. It was observed that strain levels were directly linked with strand positions. Results gave, for the studied woven hemp composite, a complete analysis of the local deformation mechanisms.

A measurement of the $ZZ$ production in the $\\ell^{-}\\ell^{+}\\ell^{\\prime -}\\ell^{\\prime +}$ and $\\ell^{-}\\ell^{+}\\nu\\bar{\\nu}$ channels $(\\ell = e, \\mu)$ in proton--proton collisions at $\\sqrt{s} = 8$ TeV at the Large Hadron Collider at CERN, using data corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected by the ATLAS experiment in 2012 is presented. The fiducial cross sections for $ZZ\\to\\ell^{-}\\ell^{+}\\ell^{\\prime -}\\ell^{\\prime +}$ and $ZZ\\to \\ell^{-}\\ell^{+}\\nu\\bar{\\nu}$ are measured in selected phase-space regions. The total cross section for $ZZ$ events produced with both $Z$ bosons in the mass range 66 to 116 GeV is measured from the combination of the two channels to be $7.3\\pm0.4\\textrm{(stat)}\\pm0.3\\textrm{(syst)}\\pm0.2\\textrm{(lumi)}$ pb, which is consistent with the Standard Model prediction of $6.6^{+0.7}_{-0.6}$ pb. The differential cross sections in bins of various kinematic variables are presented. The differential event yield as a function of the transverse momentum of the leading $Z$ boson is used to set limits on anomalous neutral triple gauge boson couplings in $ZZ$ production.

Two searches for new phenomena in final states containing a same-flavour opposite-lepton (electron or muon) pair, jets, and large missing transverse momentum are presented. These searches make use of proton--proton collision data, collected during 2015 and 2016 at a centre-of-mass energy $\\sqrt{s}=13$ TeV by the ATLAS detector at the Large Hadron Collider, which correspond to an integrated luminosity of 14.7 fb$^{-1}$. Both searches target the pair production of supersymmetric particles, squarks or gluinos, which decay to final states containing a same-flavour opposite-sign lepton pair via one of two mechanisms: a leptonically decaying Z boson in the final state, leading to a peak in the dilepton invariant-mass distribution around the Z boson mass; and decays of neutralinos (e.g. $\\tilde{\\chi}_2^0 \\rightarrow \\ell^+\\ell^- \\tilde{\\chi}_1^0$), yielding a kinematic endpoint in the dilepton invariant-mass spectrum. The data are found to be consistent with the Standard Model expectation. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.70 TeV (980 GeV).

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 TeV for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb$^{-1}$ of data collected by the ATLAS experiment and simulation of proton-proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 TeV. The impact of charged-particle separations and multiplicities on the track reconstruction performance is discussed. The efficiency in the cores of jets with transverse momenta between 200 GeV and 1600 GeV is quantified using a novel, data-driven, method. The method uses the energy loss, dE/dx, to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is $0.061 \\pm 0.006 \\textrm{(stat.)} \\pm 0.014 \\textrm{(syst.)}$ and $0.093 \\pm 0.017 \\textrm{(stat.)}\\pm 0.021 \\textrm{(syst.)}$ for jet transverse momenta of 200-400 GeV and 1400-1600 GeV, respectively.

A study of the decays B0→μ+μ− and B0s→μ+μ− has been performed using data corresponding to an integrated luminosity of 25 fb−1 of 7 TeV and 8 TeV proton--proton collisions collected with the ATLAS detector during the LHC Run 1. For B0, an upper limit on the branching fraction is set at B(B0→μ+μ−)<4.2×10−10 at 95% confidence level. For B0s, the branching fraction B(B0s→μ+μ−)=(0.9+1.1−0.8)×10−9 is measured. The results are consistent with the Standard Model expectation with a p-value of 4.8%, corresponding to 2.0 standard deviations.

The production rates of prompt and non-prompt J/psi and psi(2S) mesons in their dimuon decay modes are measured using 2.1 and 11.4 fb(-1) of data collected with the ATLAS experiment at the Large Hadron Collider, in proton-proton collisions at root s = 7 and 8 respectively. Production cross-sections for prompt as well as non-prompt sources, ratios of psi(2S) to J/psi production, and the fractions of non-prompt production for J/psi and psi(2S) are measured as a function of meson transverse momentum and rapidity. The measurements are compared to theoretical predictions.