服役后玻璃钢夹砂管力学性能及断口结构研究

Mechanical properties and fracture structure of the FRPM pipe after service

玻璃钢夹砂管作为一种新型玻璃纤维增强复合材料,已广泛应用于输水排水工程。该材料服役过程中力学性能会发生退化,进而产生管道破裂等问题,影响管道长期使用。为探究玻璃钢夹砂管服役后力学性能的变化及破坏机理,把从退役的玻璃钢夹砂管道上切割的若干轴向和环向试样分别进行抗压、抗拉和剪切性能试验,并对试样破坏后的断口进行了SEM电镜扫描分析。研究结果表明:服役后玻璃钢夹砂管的各项力学性能均有明显降低,且由于玻璃纤维主要沿环向分布,管道环向抗压、抗拉和剪切性能均优于轴向;试样断口SEM扫描电镜分析结果表明,玻璃纤维通过对试样的约束而提高其抗压强度,通过承担拉力而提高其抗拉强度,且玻璃纤维与石英砂在环向具有更好的整体性,进而玻璃纤维对环向的增强作用明显高于轴向。因此,在复杂环境和长期服役条件下,随着玻璃钢夹砂管力学性能不断退化,由于管道轴向强度相对较低,管道更易出现环向裂缝进而导致破坏。

As a new type of the glass fiber composite material,the fiberglass reinforced plastic mortar pipe(abbreviated as the FRPM pipe)has been widely applied to the water transportation and the drainage engineering.However,after service in engineering,the mechanical properties of the material will degrade,resulting in pipe cracks and other problems which affects the long-term use of the pipeline.In order to analyze the change of mechanical properties and failure mechanism of the FRPM pipes,we cut several axial and circumferential samples from the used FRPM pipes in a practical water transportation project,and then the tests on compression,tensile and shear properties are carried out respectively,afterwards the fracture locations of the samples are scanned by the scanning electron microscope.The research results show that the mechanical properties of the FRPM pipes have declined after service,and its circumferential compression,tensile and shear properties are better than those in the axial direction because the glass fiber is mainly distributed along the circular direction.The scanning electron microscope analysis of the fracture of the samples show the compressive strength of the FRPM pipes is increased by the glass fiber restraining the sample,and the tensile strength is increased by the glass fiber bearing the tensile force.The glass fiber and quartz sand have a better integrity in the circumferential direction,and the strengthening effect of the glass fiber on the circumferential direction is significantly better than that in the axial direction.Thus under the condition of complex environment and long-term service,with the degradation of mechanical properties of FRPM pipes,the pipeline is more likely to appear circumferential cracks and then cause damages due to the relatively low axial strength of the pipelines.