CAREER: Impact Resistance and Structural Health Monitoring of Bistable Composite Structures

University Of California-Davis, Davis CA

Investigators

Abstract

This project advocates the design and use of composite bistable structures, a material-based mechanism which allows delayed and controlled energy absorption. Bistable structures are developed in order to have damage distributed over a large volume instead of one localized area, with resulting greatly improved crashworthiness. Composite bistable structures are particularly attractive because it is possible to tailor them in order to have the right trade-off of strength and elongation to failure. This allows the structure to behave in a fail-safe manner, without the brittleness that typically characterizes composites. Two-dimensional bistable composite structures with high impact resistance/weight will be investigated, manufactured, tested with a drop-weight tower, analyzed through the calculation of inelastic energy curves and impact performance maps, and modeled with finite elements using the commercial software ABAQUS. The first part of the proposed research uses therefore destructive testing as a key aspect of the design such structures. In the second part of the proposed research, structural health monitoring techniques will be carried out to identify impact damage in the bistable impact-resistant structures. Damage due to impact may be invisible in routine inspections of monolithic and sandwich composites, however it dramatically affects the strength of the structure, with possible catastrophic consequences. This issue has greatly influenced people's confidence in using composites, as well as damage assessment techniques of composite structures. Increasing composite use in large structures in aerospace and civil engineering, ship construction, and automotive industries has the risk that not clearly understood failure mechanisms and undetected damage will have catastrophic consequences. Improvement of energy absorption, crashworthiness and detection of impact damage would promote and enhance the use of composites in applications where high damage tolerance and energy absorption properties are needed, for example in the design of road vehicles, rail vehicles, air and spacecraft structures, ships and submarines, on- and off-shore installations and for constructions in earthquake-prone and hazard-prone areas. Female students and students from underrepresented groups will be actively recruited. A national student competition will be held on crashworthy composites, where college students will design crashworthy structures, and students from local middle schools will compete for the design of a section of the test-rig. This latest activity will be carried out through a) the Student Development and Recruitment Office of the College of Engineering, which has a consistent track-record of recruiting underrepresented students, and b) the UC Davis Engineering Joint Council, a consortium of student representatives from the Engineering-related organizations, which is active in outreach activities.