- Title
- Impact Mechanics of Elastic and Elastic-Plastic Sandwich Structures
- Author
- Yang, Mijia
- Degree
- Doctor of Philosophy, University of Akron,
Civil Engineering, 2005.
- Advisor
- Pizhong Qiao
- Pages
- 304p.
- Abstract
- Sandwich structures are broadly used in the aerospace and automotive industries, particularly as energy absorption materials. Recent interest and application of sandwich structures in civil infrastructure provide an excellent opportunity for development and implementation of such light-weight, high energy absorption and heavy-duty sandwich materials. Most of existing studies have focused on the static responses but neglected the core deformation of sandwich structures. To capture the deformation as well as the dynamic/impact responses of sandwich structures accurately, the present study develops theoretical models for static and impact responses of beams or plates on a one-parameter Winkler foundation, a two-parameter elastic foundation, and a fully elastic medium. One unique feature of local indentation is captured through all the three models. In particular, the higher-order sandwich impact model takes into account of core inertial and decomposes the global deformation of sandwich beams into local indentation and core compression, and it can accurately capture the unequally deformed face sheets and various stresses in the sandwich structures under dynamic loading. Further, the proposed elastic impact model is extended to the case of elastic-plastic behavior. Static indentation behavior of an elastic-plastic sandwich beam is solved first, of which the effect of core crushing is considered. Then, the impact responses are solved using either the experimental or theoretically derived static bending behavior. The energy dissipated through the plasticity and indentation is recovered through the damping ratio derived. Based on the theory proposed, a set of experiments are conducted to characterize the crushing and indentation behavior of the sandwich materials, and they are later proposed to be used in the collision protection design for highway bridge girders. The crushing stresses as well as elastic-plastic indentation behavior are derived based on the experimental results, and they are integrated with impact analysis to characterize the dynamic behavior of the sandwich structures. Finally, a systematic design criteria and guideline is proposed to design this type of collision protection systems made of sandwich materials, based on different time scales of shear-off mechanism, elastic limit, and core densification limit. The combined theoretical, experimental, and numerical investigations conducted provide a validated model for impact analysis of elastic and elastic-plastic sandwich structures and shed new light on design of anti-impact and collision protection systems.
- Subject Headings
- Engineering, Civil
- Keywords
- IMPACT MECHANICS; SANDWICH; COMPOSITE; FAILURE; WAVE PROPAGATION; ENERGY ABSORPTION; ELASTIC-PLASTIC
Document number: akron1142444606.
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