摘要:
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。
Abstract:
In-plane shear testing program was designed for mullite fiber reinforced aerogel composites based on the V-notched two-rail shear method. In-plane shear and bending property tests were conducted at room temperature. Displacement and strain fields on the specimen surface were measured by approach of digital image correlation method, and mechanical behaviors and failure modes were analyzed. Results show that the testing program can obtain uniform shear strain field in the test area, so it is suitable for the in-plane shear property tests of mullite fiber reinforced aerogel composites. The in-plane shear modulus and strength obtained by tests are 248 MPa and 0.95 MPa, respectively; the bending modulus and strength are 294 MPa and 2.08 MPa, respectively. Under the in-plane shear load, the cracks initiate near the notch tips and propagate along the path between the two notches. According to the characteristic of bending normal strain distribution, it is found that the neutral plane is not coincide with the geometric symmetry plane. The characteristic of different modulus in tension and compression is validated. The neutral plane position measured by the digital image correlation method is in approximate agreement with the theoretically calculated position, and the relative error is about 10%.
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