Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session Y6: ME.2 Composites and Polymers I |
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Chair: Vasant Joshi, Naval Surface Warfare Center - Indian Head Room: Cascade II |
Friday, July 12, 2013 9:15AM - 9:30AM |
Y6.00001: A Multiphase Approach for Modeling the Shock Response of Unidirectional Composite Materials Shane Schumacher, Chris Key, Kevin Ruggirello, Scott Alexander The shock response of unidirectional fiber reinforced composite materials is inherently anisotropic due to their microstructural geometric configuration. Unlike typical elastic-plastic materials, composite materials form the observed two-wave structure under longitudinal shocks due to a precursor wave travelling through the fibers ahead of a bulk wave in the resin constituent. The nature of this response presents a problem in traditional hydrocode frameworks where each cell or material point tracks only a single velocity field. This paper outlines an adaptation of the Baer and Nunziato multi-phase model in CTH where a mixture rule is used to determine the velocity field of each constituent (fiber and matrix) of the composite material. The model modifies the momentum exchange term to represent the frictional drag forces between the fiber and matrix constituents, while assuming no mass or energy exchange. The momentum drag model is dependent not only upon the pressure difference between the constituents but also the directional dependence of the shock response. Finally, the model is implemented and compared to experimental data. [Preview Abstract] |
Friday, July 12, 2013 9:30AM - 9:45AM |
Y6.00002: The use of lateral gauges in the assessment of shear strength in a carbon fibre composite David Wood, Gareth Appleby-Thomas, Michael Goff, Nicholas Barnes, Paul Hazell, James Wilgeroth Laterally orientated manganin stress gauges have been used in obtaining the strength measurements in multiple materials, most commonly polymers and metals. Composites such as carbon fibre provide an interesting challenge for lateral gauges as any long range order within the composite will be broken up by the inclusion of the gauge. This study has investigated the shear strength of multiple orientation of a carbon fibre composite (TWCP) also compared with the matrix material of the composite investigated alone. From this data it can be ascertained whether the lateral gauge technique of measuring lateral strength is appropriate for composites with long range order. [Preview Abstract] |
Friday, July 12, 2013 9:45AM - 10:15AM |
Y6.00003: Improved understanding of the dynamic response in anisotropic directional composite materials through the combination of experiments and modeling Invited Speaker: C.S. Alexander Recently there has been renewed interest in the dynamic response of composite materials; specifically low density epoxy resin binders strengthened with continuous reinforcing fibers. This is in part due to the widespread use of carbon fiber composites in military, commercial, industrial, and aerospace applications. The design community requires better understanding of these materials in order to make full use of their unique properties. Experimental testing has been performed on a unidirectional carbon fiber - epoxy composite, engineered to have high uniformity and low porosity. Planar impact testing was performed at the Shock Thermodynamics Applied Research (STAR) facility at Sandia National Labs resulting in pressures up to 15 GPa in the composite material. Results illustrate the anisotropic nature of the response under shock loading. Along the fiber direction, a two-wave structure similar to typical elastic-plastic response is observed, however, when shocked transverse to the fibers, only a single bulk shock wave is detected. The two-wave structure persists when impact occurs at angles up to 45 degrees off the fiber direction. At higher pressures, the epoxy matrix dissociates resulting in a loss of anisotropy. Details of the experimental configurations and results will be presented and discussed. Greater understanding of the mechanisms responsible for the observed response has been achieved through the use of numerical modeling of the system at the micromechanical level using the CTH hydrocode. From the simulation results it is evident that the observed two-wave structure in the longitudinal fiber direction is the result of a fast moving elastic precursor wave traveling in the carbon fibers ahead of the bulk response in the epoxy resin. Similarly, in the transverse direction, results show a collapse of the resin component consistent with the experimental observation of a single shock wave traveling at speeds associated with bulk carbon. These results will be discussed within the context of the experiments and will be used to show where additional mechanisms, not fully described by the currently used models, are present. [Preview Abstract] |
Friday, July 12, 2013 10:15AM - 10:30AM |
Y6.00004: Development of a shock wave adhesion test for composite bonds by laser pulsed and mechanical impacts Romain Ecault, Michel Boustie, Fabienne Touchard, Michel Arrigoni, Laurent Berthe Evaluating the bonding quality of composite material is becoming one of the main challenges faced by aeronautic industries. This work aims 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 bond without any mechanical contact. The resulting damage has been quantified using different method 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 since it has often fixed parameters. That is why mechanical impacts bonded composites were also performed in this work. By changing the thickness of aluminum projectiles, the tensile stresses generated by the shock wave propagation were moved toward the composite/bond interface. The observations made prove that the optimization of the technique is possible. The key parameters for the development of a bonding test using shock wave have been identified. [Preview Abstract] |
Friday, July 12, 2013 10:30AM - 10:45AM |
Y6.00005: Shock responses of graphene reinforced composites via molecular dynamics simulations Hailin Shang, Wenqiang Wang Shock responses of graphene reinforced composites are investigated using molecular dynamics simulations. The first case studied is the response of spaced multilayer graphene plates under normal impact of a spherical projectile, focusing on the effect of the number of graphene monolayers per plate on the penetration resistance of the armor. The simulation results indicate that the penetration resistance increases with decreasing number of graphene monolayers per plate. The second case studied is the penetration resistance of laminated copper/graphene composites. The simulation results demonstrate that under normal impact by a spherical projectile the penetration resistance of copper can be improved significantly by laminating the copper plates with graphene. And the influence of graphene on the formation and growth of adiabatic shear bands in copper/graphene composites has also been discussed. The results of this research have revealed the possibility that graphene be used in the armor systems to enhance their penetration resistance. [Preview Abstract] |
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