格构式腹板增强桐木夹芯复合梁弯曲疲劳性能试验研究

Experimental study on bending fatigue behavior of wood core sandwich lattice-web composites beams

格构式腹板增强桐木夹芯复合梁因其轻质高强耐腐蚀的特性受到工程研究人员的关注,但对其疲劳特性方面的相关研究至今仍然很少。格构腹板增强桐木夹芯梁是在桐木芯材之间设置GFRP格构腹板,可有效提高复合材料夹芯梁的抗弯性能和界面性能。对GFRP格构增强的桐木复合梁进行了等分三点弯曲静载试验和疲劳试验,得到了复合桐木夹芯梁的疲劳破坏模式、疲劳寿命和损伤累积发展规律。对试件的疲劳试验的结果采用指数函数模型进行拟合,得到了格构式Ⅱ形、Ⅰ形增强试件和非格构式增强试件的指数函数、幂函数和有效缺陷模型的寿命预测计算式。格构式腹板增强的夹芯梁的挠度发展规律表现为"挠度缓慢平稳上升和累积损伤加速至破坏"两个阶段。研究结果表明,与非格构式腹板增强梁相比,设置格构式腹板对提高桐木夹芯复合梁的弯曲疲劳界面性能有重要作用,使设置格构腹板的梁在疲劳破坏前表现出明显的预兆。

Paulownia sandwich composite beams reinforced with lattice webs have attracted more and more attention of engineering field because of its light weight, high strength and corrosion resistance. However, the fatigue properties of the sandwich structure are still seldom studied. The lattice-web reinforced paulownia core sandwich structure is the structural component which has the GFRP skins and a paulownia-web core. It can effectively improve the flexural and interfacial properties of the composite sandwich beams. Three point bending static load test and fatigue test were carried out on the reinforced paulownia wood sandwich beam with lattice web, and the fatigue failure mode, fatigue life and the cumulative damage development law of the sandwich beam were obtained. The exponential function model was used to fit the fatigue test results. The life prediction formulas of three types of specimens, namely exponential function formula, power function formula and effective defect type formula, were obtained. The development law of the deflection development of the sandwich specimens undergoes two stages of ‘the slow and steady development of deflection and the acceleration of damage accumulation to failure’. The results show that compared with the sandwich beams without lattice-web, the lattice-web plays an important role in improving the bending fatigue interface performance of wood core sandwich lattice-web composite beam,and the sandwich lattice-web composite beams show obvious precursors before failure.