In this research two thicknesses of a woven CFRP laminate have been subjected to impact by a steel sphere in a velocity regime ranging from 170 m/s to 374 m/s. Impact and penetration of targets at normal and oblique incidence were studied using high speed video. For the normal incidence targets at the higher velocities of impact, a conical mass of laminate was ejected ahead of the projectile. Furthermore, despite the energy transferred to the plate increasing with impact energy, the degree of delamination in the thicker targets decreased indicating a change in projectile penetration mechanism. Eventually, the degree of delamination in the thicker targets appeared to approach an asymptotic level whereas for the thinner targets the degree of delamination appeared constant regardless of impact energy. For oblique targets more of the kinetic energy was transferred from the projectile when compared to the same thickness of target that had been subjected to a normal incidence impact. However, this was merely due to a geometrical effect. Further, thicker panels appeared to behave more efficiently by absorbing more kinetic energy per effective linear thickness at the lower impact energies Composites Part A: Applied Science and Manufacturing 39 (5), pp. 866-874 (2008) 2 where petalling is a dominant factor in the penetration. This advantage appeared to disappear as the impact energy was increased.

No abstract

WC-based ceramic metal composites ͑cermets͒ are of great importance in both armor and munition design due to the combination of properties imparted by the presence of two different phases. WC-Co cermets are of interest in this area due to the hardness and strength imparted by the WC phase while the cementing Co matrix acts to increase plasticity and toughness. Here the dynamic response of G13 WC-Co manufactured by Kennametal Engineered Products B.V. was studied via a series of plate impact experiments involving both longitudinal and lateral gauges, which allowed determination of the U s − U p relationship, measurement of a Hugoniot elastic limit of 3.3Ϯ 0.2 GPa, measurement of a spall strength of 4.38 GPa, and an investigation of the stress dependence of shear strength in such a strong material.

Knowing the dynamic behaviour of polymer materials that are used in the construction of fibre reinforced composite materials is particularly important for such materials that are subjected to impact. In this work, we have conducted a number of plate impact experiments on a commercially important aromatic amine epoxy resin that is used in the construction of carbon fibre composite materials. The measured Hugoniot in shock velocity-particle velocity space is U s = 2.65 + 1.55u p (ρ 0 = 1.141 g/cc) and is similar to the measured Hugoniots of other resins presented by different researchers. We have also measured the longitudinal stress in the shocked material and shown, in common with other polymers, that above a threshold stress, an increase in shear stress behind the shock wave is observed.

No abstract

Independently emerging fluorescence profiles of unknown, photochemically induced degradation products of several naturally non-fluorescent pesticides were monitored using single exposure excitation-emission fluorescence spectroscopy. Three-way parallel factor analysis (PARAFAC) was employed to uniquely resolve the pure fluorescent spectra of the overlapping photolysis products. The quantitative utility of EEM photolysis-based determinations was demonstrated by employing four-way PARAFAC models built from EEM time cubes of multiple fenvalerate samples. The 4-way PARAFAC models were then used to predict original pesticide concentrations resulting in conservative limit of detection and root mean square errors of calibration (RMSEC) of 3 microM each.

In-fibre measurements of the Hugoniot have been carried out on a carbon-fibrereinforced-polymer composite. For this material, we have shown at high shock stresses, a two component wave was formed consisting of a fast moving ramped portion and a slower moving shock wave. Changing the thickness of test specimen for a given shock stress resulted in a change in the magnitude and duration of the ramped portion of the wave front. As the shock stress imparted to the target was reduced, or the thickness of the target was increased, the steep shock wave in the rear surface gauge was no longer apparent. Instead a relatively slow rising wave was measured. Consequently, to establish a Hugoniot at lower shock stress levels, relatively thin specimens of target material are required.

The impact of a woven 6 mm thick CFRP laminate has been subjected to impact by an annealed steel sphere up to velocities of 1875 m/s. It was observed that above a threshold impact energy, the percentage of kinetic energy dissipated by the laminate was constant.Further, the level of damage, as measured by C-Scan and through-thickness microscopy remained constant as the impact energy was increased. However, the size of the hole formed increased. This suggested that the energy transferred to the target in the velocity range of interest became independent of the delamination. Consequently, the main energy transfer mechanism at the high velocities of impact is thought to be due to the cavity expansion and more importantly, the kinetic energy of the particulates.