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

该项目倡导设计和使用复合双稳态结构，这是一种基于材料的机制，允许延迟和可控的能量吸收。双稳态结构的发展是为了使损伤分布在大体积上，而不是分布在一个局部区域，从而大大提高耐撞性。复合双稳态结构特别有吸引力，因为可以对其进行量身定制，以便在强度和延伸率之间进行适当的权衡，以应对失败。这使得该结构能够以故障保护的方式工作，而不会出现复合材料特有的脆性。研究、制造、落锤塔试验，通过计算弹塑性能量曲线和冲击性能图进行分析，并使用商业软件ABAQUS进行有限元建模。因此，拟议研究的第一部分将破坏性试验作为此类结构设计的一个关键方面。在拟议研究的第二部分，将开展结构健康监测技术，以识别双稳态抗冲击结构的冲击损伤。在对整体和夹层复合材料的常规检查中，冲击造成的损伤可能是看不见的，但它会极大地影响结构的强度，可能会造成灾难性的后果。这一问题极大地影响了人们使用复合材料的信心，以及复合材料结构的损伤评估技术。在航空航天和土木工程、船舶建造和汽车工业的大型结构中，增加复合材料的使用可能会造成破坏机理不清楚和未发现的损伤后果灾难性的风险。改善能量吸收、耐撞性和碰撞损伤检测将促进和加强复合材料在需要高损伤容限和能量吸收性能的应用中的使用，例如在公路车辆、轨道车辆、航空和航天器结构、船舶和潜艇、陆上和近海设施以及地震多发和灾害多发地区的建筑设计中。将积极招收女学生和代表性不足群体的学生。将举行一场关于耐撞复合材料的全国学生竞赛，大学生将设计耐撞结构，来自当地中学的学生将竞争试验台部分的设计。这项最新的活动将通过a)工程学院学生发展和招生办公室开展，该办公室在招收人数偏低学生方面有着一贯的记录，以及b)加州大学戴维斯分校工程联合理事会，这是一个由工程学相关组织的学生代表组成的联盟，积极开展外联活动。

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.