陶瓷纤维增强SiO₂气凝胶复合材料面内拉伸非均匀全场应变测量与分析

By designing the circular arc edge griping scheme and dog bone type tensile specimen, the in-plane tensile property tests of ceramic fiber reinforced SiO₂ aerogel composites at room temperature were conducted. The full field deformation of ceramic fiber reinforced SiO₂ aerogel composites surface was measured and analyzed based on digital image correlation method. The non-uniform strain distribution results were obtained and discussed. The mechanical behavior characteristics and deformation and fracture mechanisms were further discussed. The results show that the in-plane tensile behavior of the ceramic fiber reinforced SiO₂ aerogel composites exhibits some nonlinear and ductile characteristics due to fiber reinforced and toughened mechanisms. Under certain load level, the strain distribution on the ceramic fiber reinforced SiO₂ aerogel composites surface shows significantly non-uniform. This is related to the internal random fiber arrangements and the different force transferring situations. In the mechanical tests, larger calculation areas can be selected for averaging treatment to reduce the non-uniform influence on the strain measurement. In the process of loading and fracture, the local strain concentration phenomenon exists on the ceramic fiber reinforced SiO₂ aerogel composites surface and evolves with the crack propagation. The fracture appearance under the in-plane tensile load has a serrated feature. It is mainly caused by the matrix fracture dominated by shear stress and the constraint effect of normal needling on the fiber layers. Results can point out the direction to improve the strengthening and toughening of thermal insulation composites.