金属材料延性对其薄膜-柔性基底结构延展性的影响

Effects of Metal Ductility on the Stretchability of Film-elastomeric Substrate Structures

自由金属薄膜轴向拉伸时的极限伸长率一般约为1%～2%,而沉积在具有一定厚度和刚度的柔性基底上的金属薄膜伸长率可能大大增加,因此此类复合结构在柔性电子器件中有较好的应用前景。采用有限元法对不同延性的薄膜-基底结构拉伸变形至其颈缩断裂过程进行了模拟,研究材料延性对其薄膜-基底延展性的影响。将内聚力模型运用到金属薄膜的断裂研究中,通过改变内聚力模型参数来模拟具有不同延性的金属薄膜。计算结果表明,脆性膜-基结构的延展性与相应的自由金属薄膜相当,而当材料延性较好时,柔性基底能起到抑制颈缩的发展,从而使膜-基结构的整体延展性得到大幅度增加,说明薄膜材料本身的延性对薄膜-基底结构的延展性具有很大影响。

When a freestanding metal film subjected to tension, the elongation at break is generally about 1% to 2%. But metal film deposited on an elastomeric substrate with certain thickness and stiffness can usually be stretched to a large strain. Therefore such metal film-substrate structures have been prospective used in flexible electronic devices. To study the effects of the ductility of metal films on the stretchability of metal film-substrate structures, the entire process of stretching of the structure to film necking was modeled and analyzed by finite ele- ment method. Film fracture was simulated by application of cohesive zone model（CZM）. Different ductility of metal film was approximated by adopt corresponding CZM parameters. The results show that the stretchability of the film-substrate structure is almost the same as that of freestanding thin film when the film is brittle. However, for the necking being suppressed by the substrate, the stretchability is greatly enhanced as the film getting more ductile. It is demonstrated that material ductility of film plays important role in stretchability of the film-elasto- meric substrate structures.