多轴向增强拉挤复合材料木夹芯梁弯曲试验

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.