黏弹性薄膜/基底系统界面黏附性能影响因素的实验及理论研究

The applications of viscoelastic thin film/substrate system are restricted significantly due to the absence of the corresponding theories. In this study, the adhesion of a viscoelastic thin film on substrate will be investigated by the peel test experiment combining theoretical analysis. Firstly, the peel test of a viscoelastic thin film adhering on substrate will be conducted systematically. The effects of loading velocity, peeling angle and the surface physical properties of substrate on adhesion will be mainly considered. The geometries of the cohesive zone will be measured by the in-situ images, with which the effective adhesion length and the size effect of the viscoelastic film can be studied. Rate-dependent interfacial properties of thin film/substrate can be analyzed by comparing the adhesion of a viscoelastic thin film with that of an elastic one. Secondly, the adhesion mechanisms of a multilayer thin film/substrate will be further measured. The peeling failure at different interfaces can be controlled by analyzing the efffects of loading velocity, pre-stress in the film and peeling angle on the adhesion, and the underlying mechanisms will be explained. Lastly, theoretical and numerical models will be established to analyze the peeling behaviors of one layer and multilayer thin film structures, and the results will be compared with the experimental ones, with which the adhesion mechanism of viscoelastic thin film is clarified. Combining the adhesion of elastic thin film and the results of the present study, it can not only provide theoretical foundations for designing the reversible adhesion for one layer of the viscoelastic thin film and the controllable failure at different interfaces for the multilayer thin film/substrate structure, but also can develop the viscoleastic surface/interface adhesion mechanics.

黏弹性薄膜撕脱理论的缺乏极大限制了黏弹性薄膜/基底系统的应用。本项目将通过黏弹性薄膜撕脱实验，并建立有效的黏弹性薄膜撕脱理论模型，系统研究黏弹性薄膜/基底结构的界面黏附行为。首先，开展黏弹性薄膜撕脱实验，研究加载率、撕脱角、基底表面性质等因素对撕脱行为的影响；实时在位测量内聚力区几何参数，分析黏弹性薄膜有效黏附长度的影响因素及尺寸效应；比较不同加载速率下黏弹性薄膜与弹性薄膜的撕脱行为，揭示界面黏附性质的率相关性；其次，实验测量多层薄膜/基底结构的黏附行为，分析加载率、预应力及撕脱角等因素对不同界面撕脱的控制行为，阐明其中的影响因素及物理机制；最后，建立并分析单层黏弹性薄膜和多层薄膜撕脱的理论与数值模型，与实验结果比较，阐明影响黏弹性薄膜黏附撕脱的主要因素。结合已有弹性薄膜撕脱理论与本项目研究成果，为设计单层薄膜可逆黏附及多层薄膜可控脱黏提供理论指导，并能促进黏弹性表/界面黏附力学发展。

薄膜/基底系统由于简单而有效被广泛用于表征界面黏附性能，但由于黏弹性薄膜撕脱理论的缺乏极大限制了黏弹性薄膜/基底系统的应用。本项目首先系统开展了黏弹性薄膜的撕脱实验，得到了典型撕脱力-位移曲线，并考虑了加载速率、撕脱角、薄膜厚度、基底粗糙度等因素对撕脱力的影响，实时在位测量了内聚力区的尺寸，发现黏弹性薄膜有效黏附长度随加载速率和薄膜厚度的增大而增大；进一步建立理论模型得到了黏弹性薄膜撕脱时的能量释放率。应用最小势能原理，理论研究了弯曲刚度和基底粗糙度对薄膜撕脱行为的影响，分析了薄膜在基底上的整个撕脱过程，解析得到了撕脱力-位移关系和薄膜构型变化。结果表明，弯曲刚度对薄膜起始脱黏时的撕脱力影响显著，此时撕脱力随着薄膜刚度的增大而增大；弯曲刚度对薄膜稳态撕脱力基本没有影响，但稳态时最大撕脱力随着基底粗糙度的增大而增大。进一步考虑了环境湿度对薄膜界面黏附的影响，发现当相对湿度小于90%时，基底上吸附的单分子厚度水膜与固体表面间较强的分离压力将增强界面黏附；当相对湿度大于90%时，水分子将在界面裂纹尖端凝结成液桥，此时，液桥产生的毛细力对界面黏附影响复杂，根据固-液界面能、固-气界面能、液-气界面能的不同，将增大或减弱界面黏附力。此外，初步研究了多层薄膜的界面黏附行为，发现可以通过控制黏弹性薄膜的加载速率或弹性薄膜的刚度实现在不同界面脱黏。通过以上研究，阐明了影响黏弹性薄膜界面黏附的主要因素，拓展了经典Kendall薄膜撕脱理论。该结果为设计单层薄膜可逆黏附及多层薄膜可控脱黏提供了理论基础，并能促进黏弹性表/界面黏附力学的发展。