胶合板梯度胶合界面应变的数字散斑法分析

研究了均质、薄壳和内增强3种结构胶合板的断面密度分布, 根据密度分布确定梯度界面,并运用数字散斑法分析胶合板老化前后的密度梯度层胶合界面处的应变分布,以探讨梯度胶合对胶合界面应变传递的影响。试验结果表明:均质结构的胶合板断面密度分布较均匀,基本在0.83 g/cm³左右,而薄壳和内增强结构的胶合板断面密度显示两者均有明显的密度梯度和弱界面的存在。在450 N左右的载荷作用下,各密度梯度层胶合界面处的剪切变形最大值均出现在胶线两端的槽口处,并沿胶线方向逐渐减小。密度梯度层的应变主要表现为高密度层的应变通常大于低密度层的应变。老化后试件胶合界面的应变值普遍减小,高密度层的减小较小,反映了高密度层耐老化性能强于低密度层。

Investigation of strain of gradient density interface of plywoodusing digital speckle correlation method

The vertical density profile, density gradient and interface of three types of plywood, namely homogeneous, thin shell and inner strengthened structures, were investigated in this study. Strain distributions of different gradient density interfaces before and after the aging process were measured by the digital speckle correlation(DIC)method. Experiment results showed that the density of the homogenous structure plywood was relatively uniform, measuring about 0.83 g/cm³. Large density gradient and weak interface existed on the cross sections of both shell and inner strengthened structure plywood. Under a load of about 450 N, the maximum shear strain occurred near the notches at both ends of the bonding interface and shear strain decreased along the bond line to the middle zone. Generally, the shear strain of the higher density layer of gradient interface was greater than that on the lower density layer of the specimens. After aging, the shear strain on the bonding interface decreased compared with the control group. The higher density layer of the gradient interface of specimens had greater resistance to aging process, which was resulted from its slower strain decrease than that on the lower density layer on the gradient interfaces.