Residual Stressesin intrinsic hybrid laminates, detection, modification and consideration in manufacturing and the numeric damage modeling

复合材料各组分热性能的差异和各向异性导致了复合材料生产过程中固有的高残余应力，从而降低了复合材料的强度。该项目旨在研究降低层间应力的措施。因此，研究了测量现有或新生残余应力的测量技术。重点是将光纤传感器直接集成到未固化的纤维增强聚合物中的应用。随后研究了修正残余应力水平的措施。参数质量筛选揭示了材料参数与工艺参数以及层间残余应力之间的因果关系。除了固有应力外，不对称的铺层还会导致工艺引起的变形，如曲率或挠度。弯曲结构表现出显著的复杂应力状态。开发的测量原理将被调整，以便在残余应力的测定之外，可以对过程引起的变形的来源作出陈述。利用第一个资助期获得的关于残余应力来源、不同内在和外在因素的影响的认识，发现由结构曲率、不对称引起的过程诱导变形与嵌入残余应力之间的因果关系。除了减少应力的措施外，还研究了混合结构尺寸精确结构的补偿方法。利用所开发的补偿方法，制作了用于CAI研究的精确的平面非对称板。对损伤行为的影响将进行实验研究。

The different thermal properties of the components as well as the anisotropy of hybrid CFRP-metal-composites lead to intrinsic high residual stresses during the production processes reducing in turn the strength of the hybrid composite. The project aims to investigate measures to reduce the interlaminar stresses. Therefore, measurement technologies are investigated for measuring the existing or nascent residual stresses. The focus lies on the application of fiber optical sensors being directly integrated into the uncured fibre reinforced polymer. Measures for modifying the level of residual stresses are investigated subsequently. Parametric mass screenings reveal the cause-effect relationships between the material parameters and the process parameters as well as the interlaminar residual stresses.Beside the intrinsic stresses asymmetric layups lead to process-induced deformations like curvatures or deflections. Curved structures exhibit significant complex stress states.The developed measurement principle will be adapted such that beside the determination of the residual stresses statements about the sources of process-induced deformation can be made. The achieved perceptions from the first funding period about the origin of residual stresses, the influence of different intrinsic and extrinsic factors are used to discover the cause-effect relationships between the process-induced deformation evoked by the structural curvature, the asymmetry, and the embedded residual stresses. Beside measures for reducing these stresses compensating methods for producing dimensionally accurate structures are investigated for hybrid structures. The developed compensating methods are used to manufacture accurate flat asymmetric coupons for CAI investigations. The effect on the damage behavior will be investigated experimentally.