多轴向增强拉挤复合材料木夹芯梁弯曲试验

Bending test of multi-axial reinforced pultruded composite wood-cored beam

为解决传统GFRP(玻纤增强复合材料)型材的节点弱、刚度低等缺陷问题,提出一种以花旗松为芯材、以多轴向GFRP为外壳的新型拉挤复合材料夹芯梁,对比研究了木梁、GFRP空管梁和GFRP木夹芯梁的四点弯曲性能,采用声发射监测梁的损伤演变.结果表明:木梁发生受拉破坏,空管梁的腹板和上翼缘发生屈曲、褶皱,夹芯梁面层发生褶皱破坏;相比木梁和空管梁,夹芯梁的极限承载力最大提高约250%和50%,抗弯刚度最大提高约160%和90%;单向布增强梁的强度和刚度最低,三向布可兼顾梁的抗弯刚度和横向强度,延缓发生腹板-翼缘分离.声发射研究表明:累积能量、累积撞击数和荷载的时程曲线有较好的一致性,累积撞击数率比反映了梁的微观损伤累积程度,累积能量率比反映了梁的宏观损伤特征.

To overcome the disadvantages such as week joint property and low stiffness in traditional GFRP(glass fiber-reinforced polymer)sections,a novel pultruded sandwich beam with a Douglas-fir core and a multi-axial GFRP facesheet was presented.The four-point bending performance of the timber beams,GFRP hollow tube beams and GFRP wood-cored sandwich beams were comparatively investigated,while the damage evolutions were monitored by the acoustic emission.Results show that the timber beam fails by the tensile rupture,the hollow tube beam fails by the buckling and wrinkling of the web and upper flange,and the sandwich beam fails by the wrinkling of the skin.Compared with the ultimate strength of timber and hollow tube beam,the ultimate strength of sandwich beam increases maximally by 250%and 50%,respectively,while the stiffness increases maximally by 160%and 90%,respectively.The beam with uniaxial fabric have lowest strength and stiffness,and the tri-axial fabric reinforcement could keep sufficient bending stiffness while providing better transverse strength to avoid the premature web-flange separation.The acoustic emission research results show that the time-history curves of accumulative energy and hits are well consistent with the load curve,and the accumulative hits rate ratio exhibits the accumulative micro-damage degree while the accumulative energy rate ratio shows the macro-damage character of the beams.