| A critical review of the Hopkinson bar experimental technique is performed to identify the validity and applicability of the classic one-dimensional theory. A finite element model of the Hopkinson bar experiment is developed in three-dimensions and is used in detailed numerical analyses. For a small diameter hard specimen, the bar-specimen interfaces are non-planar, which predicts higher specimen strain and, thus, lower initial modulus in the linear elastic phase of deformation. In such cases, the stress distribution in the specimen is not uni-axial and a chamfered specimen geometry is found to provide better uni-axial stress condition in the specimen. In addition, a new Hopkinson bar with transmission tube is found suitable for small strain measurement of small diameter specimens. A one-dimensional exact Hopkinson bar theory considering the stress wave propagation in an equal diameter specimen has been formulated which predicts physically meaningful results in all extreme cases as compared to classic theory.; In light of the theoretical and numerical investigations, an experimental methodology for rate dependent modulus and strength is developed. Quasi-static and dynamic behavior of plain weave (15 x 15) S-2 glass/SC15 composites has been investigated. A new circular-rectangular prism specimen (C-RPS) geometry is found suitable for testing laminated composites in the in-plane directions. Rate sensitive strength, non-linear strain and elastic modulus parameters for plain-weave (15 x 15) S-2 glass/SC15 composites have been experimentally determined. |
