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基于V型缺口试样双轨剪切法设计了面内剪切试验方案,开展了莫来石纤维增强气凝胶复合材料的室温面内剪切和弯曲性能试验,采用数字图像相关方法对试样表面的位移场和应变场进行测量,并分析了力学行为和破坏模式。结果表明:设计的试验方案可以在测试区域获得均匀的剪切应变场,适用于莫来石纤维增强气凝胶复合材料的面内剪切性能测试。试验获得的面内剪切模量和强度分别为248 MPa和0.95 MPa,弯曲模量和强度分别为294 MPa和2.08 MPa。面内剪切载荷下,试样的裂纹萌生于缺口尖端附近,并沿两缺口连线方向扩展。根据弯曲正应变场的分布特点,发现试样中性层与几何对称面不重合,验证了该材料拉压模量不同的性质。采用数字图像相关方法获得的中性层位置和理论计算值比较接近,相对误差在10%左右。
The in-plane shear test scheme was designed based on the dual-track shear method of V-notch specimens. The in-plane shear and flexural properties tests of mullite fiber reinforced airgel composites were carried out. The digital image correlation method The surface displacement field and strain field were measured, and the mechanical behavior and failure modes were analyzed. The results show that the designed test scheme can obtain uniform shear strain field in the test area and is suitable for the in-plane shear testing of mullite fiber reinforced airgel composites. The in-plane shear modulus and strength obtained were 248 MPa and 0.95 MPa, respectively, and the flexural modulus and strength were 294 MPa and 2.08 MPa, respectively. Under in-plane shear loading, the crack initiation in the specimen occurs near the notch tip and propagates along the direction of the two notch connections. According to the distribution characteristics of normal strain field, it is found that the neutral layer does not coincide with the geometric symmetry plane, which verifies the different tensile properties of the material. The neutral layer position obtained by using the digital image correlation method is close to the theoretical calculation value with a relative error of about 10%.