不同载荷方式下MDYB-3有机玻璃的变形与破坏行为

Deformation and Failure Behavior of MDYB-3 Oriented PMMA Glass Under Different Loading Conditions

为了理解和评价MDYB-3定向有机玻璃的力学行为,采用CSS44100电子万能试验机,分离式Hop-kinson技术和MTS液压伺服试验机分别进行了5种不同类型的力学试验。这些试验包括力学各向异性试验、穿孔试验、应变率从0.001s-1到2000s-1和初始温度从218K到373K的单轴拉、压试验、等幅应力控制下不同应力集中系数的双边缺口试样疲劳试验。同时采用光学显微镜对变形试样的破坏和断裂进行了观察和分析。结果表明:①MDYB-3定向有机玻璃呈现明显的各向异性性能;②沿板面法线方向MDYB-3定向有机玻璃具有更高的硬度和强度,在穿孔或冲击条件下它以脆性分层破裂和散落为破坏形式;③MDYB-3定向有机玻璃的力学响应强烈地依赖于应变率和温度,且在拉伸和压缩加载下表现出很大的强度非对称性;④双边带有缺口试样的S-N曲线表明,最大应力幅值较低时,MDYB-3定向有机玻璃的疲劳寿命对缺口不敏感。在循环载荷下裂纹起源与微层特性及层间强度有关,它起源于层间可处在缺口中段部位,最后文中对变形与破坏机理也进行了分析和讨论。

To understand and evaluate the thermomechnical behavior of MDYB-3 oriented PMMA glass,five different types of mechanical tests are carried out using a CSS44100 universal electromechanical material testing machine,the split Hopkinson technique and an MTS servohydraulic testing machine. These tests include：mechanical isotropic testing;perforation tests;uniaxial compression and tension tests over the strain range from 0.001 s-1 to 2 000 s-1 and at initial temperatures from 218 K to 373 K;and constant amplitude stress controlled fatigue testing with two notch stress concentration factors. The damage and fracture of the deformed samples are also observed by a digital camera and an optical microscope. The results show：① MDYB-3 oriented PMMA glass has remarkable thermomechanical anisotropic characteristics;②MDYB-3 oriented PMMA glass exhibits higher hardness and strength along the normal direction of the panel,but it will burst out and scatter into brittle pieces under perforation or impact;③Its thermomechanical responses depend strongly on strain rates and temperatures,and it also shows severe unsymmetry of mechanic strengths under tension and compression loading;④The S-N curves of double-notch sheet specimens demonstrate that the fatigue life is not sensitive to the notch at low maximium amplitude stress levels,and that in cyclic loading,the crack initiaton origin is related with the strength of micro-interbeds. Crack initiation of MDYB-3 oriented PMMA glass may originate from the interbeds or the middle region of the notch edge under cyclic fatigue loading. Finally,the results are analyzed and discussed.