Failure of steel sandwich structures in compression: Modelling and testing

运输业是全球温室气体排放的重要贡献者。航运业目前约占二氧化碳排放量的3%，预计到2050年这一数字将上升到18%。如果我们能减轻车辆的重量，我们就会减少燃料消耗。在一些类型的船舶中，结构钢重量占总重量的比例很大，例如集装箱船、渡轮和邮轮的重量比例为40%-60%。通过使用轻量化的结构可以减轻一些重量。钢夹芯板重量轻、价格相对低廉、可回收利用，很容易在船舶等大型建筑中使用，也可以在桥梁和建筑物中使用。一种易于大规模生产的类型是将芯中的单向加强筋激光焊接到面板上的类型。核心形状的高度优化版本包括垂直加强筋，即所谓的腹板，形成腹板-核心夹层板。为了能够安全地使用这些面板作为承重构件，需要更好地了解它们的力学行为。这项建议集中在平面内压缩载荷下的破坏，包括单轴和双轴。这种行为是复杂的、非线性的，受许多因素的影响。这些板对垂直于腹板的荷载特别敏感，因为核心中的空隙可能是空的，这导致非常低的横向剪切刚度，并导致独特的结构特征。我们将用数值方法和实验方法来研究这种行为。此外，这一建议旨在开发一种有效的强度预测方法，该方法可以模拟大型装配(如船舶)中的破坏过程和载荷对周围结构的重新分配。该方法将基于等效单层理论(ESL)和非线性均化刚度。该方法将通过商业有限元软件中的用户自定义子程序来实现，因此设计公司不需要购买额外的软件包。与面板的拓扑被显式建模的替代有限元分析相比，节省的时间是巨大的。厚面效应和修正的偶应力理论在板的剪切刚度很低的情况下，以及在连续介质假设不严格成立的情况下，可能会在ESL方法中使用。此外，还将制定极限强度的方法，从而能够确定面板的储备强度，即首次失效和最终失效之间的差值。所开发的方法将通过实验进行验证。测试将首次在全尺寸电池板上进行。该研究计划将培养工程师，他们将专门从事固体力学的数值和实验方法，并将拥有广泛的结构分析理解。

The transportation industry is a significant contributor to global green-house gas emissions. The shipping industry in specific currently accounts for approximately 3% of CO2 emissions, and this number is predicted to rise to 18% by 2050. If we can reduce the weight of vehicles, we will reduce the fuel consumption. In some types of ships, the ratio of structural steel weight to total weight is very large, for example 40-60% in container ships, ferries and cruise ships. It is possible to decrease some of that weight by using lightweight structures. Steel sandwich panels are lightweight, relatively cheap, recyclable and easy to implement in large structures like ships, but also bridges and buildings. A type which is easy to produce on a large scale is one where unidirectional stiffeners in the core are laser-welded to the face plates. A highly optimized version of the core shape consists of vertical stiffeners, the so-called webs, forming a web-core sandwich panel. In order to be able to use these panels as load-carrying members safely, their mechanical behaviour needs to be better understood. This proposal focuses on their failure under in-plane compressive loading, both uni-axial and bi-axial. The behaviour is complex, non-linear and influenced by numerous factors. These panels are especially sensitive to loading perpendicular to the webs, since the voids in the core can be empty, which results in very low transverse shear stiffness and causes unique structural features. The behaviour will be studied using numerical and experimental methods. Furthermore, this proposal aims to develop an effective strength prediction method that can model the progress of the failure and the load redistribution to the surrounding structure in a large assembly, e.g. a ship. The method will be based on equivalent single-layer theory (ESL) and nonlinear homogenized stiffnesses. The method will be implemented via user-defined subroutine in commercial finite element method (FEM) software, thus the design companies do not need to purchase additional software packages. The time savings are enormous in comparison with alternative FEM analyses where the topology of the panels is explicitly modelled. Thick-face effect and modified couple stress theory will be potentially used within the ESL method in the case of very low shear stiffness of the panels and for cases where continuum assumption is not strictly valid. In addition, methods for ultimate strength will be developed, which will allow the determination of the reserve strength of the panels, i.e. the difference between first and final failure. The developed methods will be validated with experiments. For the first time the tests will be carried out on the full-scale panels. The research program will train engineers who will be specialized in numerical and experimental methods in solid mechanics and will possess a broad understanding of structural analysis.