High Modulus and High Strength C/C-SiC Ceramic Matrix Composites by Fiber-Matrix Interface Tailoring via Modification of Fiber Surface and Matrix Precursor - Kerafam 2

基于之前的KeraFaM项目中获得的知识，KeraFaM 2旨在使C/C-SiC材料的力学性能更接近标准和高性能纤维的理论极限。到目前为止，获得了以下见解：·通过对纤维基质粘合(FMB)的精确定制，可以实现在硅化过程中保护纤维免受转化的影响。这防止了纤维-基质-分层(FMD)，并有利于纤维束之间的分段裂纹(SC)，导致致密的C/C-块被碳化硅基质隔开。所得C/C-SiC复合材料的力学性能均低于理论极限。纤维性能的低利用率归因于有利于纤维束拔出的C/C块结构。·碳化后观察到的样品裂纹结构的形成在树脂固化过程中就已经开始了。·基质树脂的选择影响了微观结构。树脂之间的本质区别在于酚醛和溶剂的含量。·项目中使用的超高模数(UHM)纤维由于脆性而无法在退浆后加工。·不同FMB在热解过程中的微裂纹形成可以用有限元方法(FEM)建模。斯图加特DLR、登肯多夫DITF和奥格斯堡大学实验物理2主席的团队陶瓷复合材料和结构之间的合作已被证明在KeraFaM期间是兼容和有效的。在这次成功合作的基础上，KeraFaM 2将实现以下目标：·为了提高光纤利用率，打算对C/C块进行子结构。这可以通过多层施胶来实现。这种施胶用于获得更明确的FMB裁剪，并保护纤维不被转换。在第二种方法中，将生产微孔C-基质。这两个概念预计都有利于单纤维拔出而不是纤维束拔出。·从树脂固化阶段开始的交联反应分析、原位声发射分析和纳米CT检查解决了对微观结构形成的理解。这最终将导致更好地控制微结构和由此产生的C/C-碳化硅复合材料的性能。·有限元模型将通过考虑实验获得的材料参数进行改进，以便真实地表示不同FMB值下的微结构发展。所得模型将通过声发射分析和扫描电子显微镜测量进行验证。·碳化后基质树脂的酚类含量对残碳量、收缩和微观结构的影响将通过改变基质树脂中芳香族化合物的比例进行评估。·为了进行进一步加工并防止纤维转化为碳化硅，UHM纤维将在现有上浆的基础上进行额外上浆。

Based on the knowledge gained in the previous KeraFaM project, KeraFaM 2 aims to bring the mechanical properties of C/C-SiC materials closer to the theoretical limits expected from standard and high performance fibers.So far, the following insights were obtained:•Protection of the fibers against conversion during the siliconisation can be achieved by precise tailoring of the fiber-matrix-bonding (FMB). This prevents fiber-matrix-delamination (FMD) and favors segmentation cracks (SC) between fiber bundles, resulting in dense C/C-blocks separated by SiC matrix. Mechanical properties of the resulting C/C-SiC composites are below the theoretical limits. The low utilization rate of fiber properties is attributed to the C/C block structure favoring a fiber bundle pullout.•The formation of the crack structure of the samples observed after carbonization does already start during curing of the resin.•The choice of matrix resin influences the microstructure. The essential difference between the resins are the phenolic and solvent content.•The Ultra High Modulus (UHM) fibers used during the project could not be processed after desizing due to their brittleness.•The micro crack formation for different FMBs during pyrolysis can be modeled employing the Finite Element Method (FEM).The collaboration between the team ceramic composites and structures at the DLR in Stuttgart, the DITF in Denkendorf and the chair of experimental physics 2 at the University of Augsburg has proven to be complementery and effective during KeraFaM. Based on this successful collaboration, the following goals will be pursued in KeraFaM 2:•To raise the fiber utilization rate substructuring of the C/C blocks is intended. This could be achieved by a multilayer sizing. This sizing is used to obtain a more defined tailoring of the FMB and to protect the fibers from conversion. In a second approach a microporous C-matrix will be produced. Both concepts are expected to favor single fiber pullout over fiber bundle pullout.•Analysis of cross-linking reactions, in situ acoustic emissions analysis and nano-CT examination starting at the curing stage of the resin addresses understanding of the microstructure formation. This will ultimately lead to better control of the microstructure and the resulting C/C-SiC composite properties.•The FE-Model will be refined by taking into account experimentally obtained material parameters in order to realistically represent microstructure development for different FMB values. The resulting model will be validated by acoustic emissions analysis and SEM measurements.•The impact of phenolic content of the matrix resins on residual carbon mass, shrinkage and microstructure after carbonization will be evaluated varying the proportion of aromatic compounds of the matrix resin.•To allow further processing and to protect fibers from conversion to SiC, UHM fibers will be modified by applying an additional sizing on top of the as-received sizing.