Manufacturing, testing and modelling of hybrid aluminium foam - CFRP sandwiches with improved impact strength

夹层材料在汽车和铁路交通中的结构应用中，经常需要调查碰撞和碰撞安全性，以确保乘客的安全和车辆结构的完整性。广泛分布的纸芯夹层复合材料往往缺乏结构应用所需的高压缩和高冲击强度。抗剪切金属泡沫芯材和碳纤维增强面板的混合夹层复合材料提供了巨大的能量吸收潜力。此外，混合轻量化设计的方面通过多层高韧性面板得到加强。因此，在本提案中，重点说明了CFRP-Al泡沫三明治的重要方面。首先，对适合于批量生产的新型PU喷涂工艺进行了面片沉积工艺的优化。其中，针对轻量化设计，研究了不同的材料组合和影响工艺稳定性的因素。然后使用静态和动态材料测试对这些材料进行表征，以提供芯材、面板及其界面中弹性和塑性变形的详细机械性能。使用这些变量可以对实际应用和加载过程中的力学行为做出基本结论，并可以识别工艺、结构和力学性能之间的关系。根据多材料体系的中心作用，结构表征将进一步发展。尤其是层析测量方法，由于其在三维图像分析、损伤演化表征和细观细观结构分析方面的优势，将被应用和加强到混杂夹层复合材料中。在材料测试和结构表征中研究的实验数据最终建立了支持夹层复合材料的微观力学模型和结构完整性和复合材料部件的设计细节的基本见解。到目前为止，用于传统夹层结构的模型必须根据结构发现和测量的部件性能调整到材料组合，然后将其与夹层结构的力学性能进行比较，并用夹层试验的实验数据进行验证。最终目标是全面了解基于界面和相互作用的材料组合和影响，为上述应用领域的夹层零件尺寸提供指导和数据。

The usage of sandwich materials in structural applications in the automotive and railway traffic is in constant need of surveying the crash and impact security to ensure the safety of passengers and vehicle structural integrity. The wide spread paper-core based sandwich composites often lack the high compression and impact strength needed for structural applications. Hybrid sandwich composites of shear-resistant metallic foam cores and carbon fiber reinforced face sheets provide an enormous potential of energy absorption. Additionally the aspect of hybrid lightweight design is enhanced through multilayer build up with high tenacity face sheets. Therefore in this proposal the important aspects of CFRP-Al-foam sandwiches are focused and illustrated. First of all the optimization of the face sheet deposition is performed for the innovative PU spraying process which is suitable for series production. Therein different material combinations and influence factors on the process stability are investigated for lightweight design. These are then characterized using static and dynamic material testing to provide detailed mechanical properties of elastic and plastic deformation in the core, face sheet and their interface. Using these variables basic conclusions about the mechanical behavior during real life application and loading can be made and the relations between process, structure and mechanical properties can be identified. The structural characterization will be further developed according to the central role for the multi material system. Especially tomographic measurement methods will be applied and enhanced to hybrid sandwich composites due to their advantages of 3D image analysis for damage evolution characterization and micro- and meso-structural analysis. The experimental data studied in material testing and structure characterization finally builds the fundamental insight supporting a micro-mechanic modelling of the sandwich composite and design details for structural integrity and composite parts. The models used so far for conventional sandwich structures have to be adjusted to the material combination based on the structural findings and the measured component properties which will then be compared to the mechanical behavior of the sandwich structure and validated with the experimental data from sandwich testing. The final objective is a comprehensive understanding of the material combination and the effects based on the interface and mutual interaction providing guidelines and data for the dimensioning of sandwich parts in the afore mentioned application area.