Z-pin增强复合材料层合板断裂韧性试验研究

针对Z-pin增强复合材料层合板, 开展了断裂韧性的试验研究。研究选取了3种Z-pin直径(0.28、 0.52、 0.80mm)且每种直径下分别以3种分布形式(5×5、 8×8、 10×10)排布Z---pin的增强方式, 为了确定比较基准, 试验中同时测试了不含Z-pin的复合材料层合板试样。通过Z-pin拔出试验测试了3种直径Z-pin从基体拔出过程中的载荷位移关系。利用双悬臂梁试验和端部开口弯曲试验分别测试了不含Z-pin和含Z-pin试样的Ⅰ型断裂应变能释放率G_ⅠC、 Ⅱ型断裂应变能释放率G_ⅡC。试验结果表明:? 与不含Z-pin的结构相比, Z-pin增强试样的Ⅰ型断裂应变能释放率G_ⅠC增大了83%~1110%, Ⅱ型断裂应变能释放率G_ⅡC增大了23%~438%; 在相同Z-pin体积含量下, 与增大Z-pin直径相比, 增大Z-pin分布密度能更有效地提高复合材料层合板的断裂韧性。 

Experimental investigation on the fracture toughness of Z-pins reinforced composite laminates

The fracture toughness experiments of Z-pin reinforced composite laminates were carried out. Pull-out test of Z-pins of different diameters（0.28, 0.52, 0.80mm）embedded into unidirectional laminate coupons was conducted to measure the curves of Z-pin bridging force versus pull-out displacement. Then, the mode Ⅰ and mode Ⅱ fracture toughness of Z-pinned laminates and unpinned laminates were tested respectively using the double-cantilever-beam (DCB) method and three point edge-notched-flexure (ENF) methods. Comparison was made for the measured mode Ⅰ and mode Ⅱ strain energy release rates between two types of laminates. Strain energy release rates GⅠC and GⅡC of Z-pin reinforced laminates are higher from 83% to 1110% and from 23% to 438% than those of unpinned laminates respectively. Moreover, the test results denote that enlarging the Z-pin distributive density is more effective to reinforce structural strain energy release rate than enlarging Z-pin diameter at the same volume fraction.