Browsing by Author "Cooper, G."

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    The dynamic behaviour of a modified polyurethane resin
    (2011-06-15) Appleby-Thomas, Gareth J.; Hazell, P. J.; Stennett, C.; Cooper, G.; Cleave, R.
    The dynamic response of both a pure and nano-reinforced polyurethane replacement resin (PRR) have been investigated using plate impact techniques. Similar U-P-U- S Hugoniot equations of state have been established for both materials, despite the altered cross-linking associated with the addition of inorganic polyhedral oligomeric silsesquioxane (POSS) blocks of c. 1.5 nm size to the resin matrix. At higher particle velocities a similar U-P-U-S response to that of polyurethane from the literature was observed. However, at lower particle velocities a non- linear response was noted in both forms of PRR, similar to that observed for polymers elsewhere. Ultrasonic measurements were also undertaken and indicated the presence of two distinct phases in the reinforced elastomer.
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    The effect of specimen thickness on the shock propagation along the in-fibre direction of an aerospace-grade CFRP laminate
    (Elsevier, 2009-02) Hazell, P. J.; Stennett, C.; Cooper, G.
    In-fibre measurements of the Hugoniot have been carried out on a carbon fibre-reinforced 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.
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    Normal and oblique penetration of woven CFRP laminates by a high velocity steel sphere
    (Elsevier Science B.V., Amsterdam., 2008-05-31T00:00:00Z) Hazell, P. J.; Kister, G.; Stennett, C.; Bourque, P.; Cooper, G.
    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 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 where petalling is a dominant factor in the penetration. This advantage appeared to disappear as the impact energy was increased.
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    The shock and release behavior of an aerospace-grade cured aromatic amine epoxy resin
    (John Wiley & Sons, Ltd, 2008-06-20T00:00:00Z) Hazell, P. J.; Stennett, C.; Cooper, G.
    Knowing the dynamic behavior of polymer materials that are used in the construction of fiber-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 fiber composite materials. The measured Hugoniot in shock velocity–particle velocity space was Us = 2.65 + 1.55 up ( ρ0 = 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 strength with impact stress is observ
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    Shock propagation in a cemented tungsten carbide
    (American Institute of Physics, 2009-12-31T00:00:00Z) Appleby-Thomas, Gareth J.; Hazell, P. J.; Stennett, C.; Cooper, G.; Helaar, K.; Diederen, A. M.
    WC-based ceramic metal composites (cermets) 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 Us−Up relationship, measurement of a Hugoniot elastic limit of 3.3±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