Bridging between micromechanics response and macroscopic behavior is at the core of multiscale investigations in heterogeneous materials. As such, quantitative characterization of the transitional length scales that correlate micro and macroscale behaviors is of great importance. Experimental characterization of the so-called transitional length scales in foams and other cellular structures is extremely scarce. The present work reports on an experimental-statistical approach proposed to quantify the micro-to-macro transition length scale in polymeric foams. The approach proposed in this work uses full-field strain distributions measured by digital image correlation (DIC) at two scales as input. The physical dimensions of the transition length scale are identified by implementing a statistical algorithm based on spatial averaging of the local strain data obtained from DIC. Interestingly, the transition between micro and macroscale deformation is found to be a function of material density but independent of global strain and stresses applied. The present results provide direct validations to representative volume element (RVE) size in cellular solids determined by computational methods.

微观力学响应和宏观行为之间的桥梁是异质材料多尺度研究的核心。因此，与微观和宏观行为相关的过渡长度尺度的定量表征非常重要。泡沫和其他多孔结构中所谓的过渡长度尺度的实验表征极其稀少。目前的工作报告了一种实验统计方法，用于量化聚合物泡沫中的微观到宏观转变长度尺度。这项工作中提出的方法使用通过数字图像相关 (DIC) 在两个尺度上测量的全场应变分布作为输入。过渡长度尺度的物理尺寸是通过实现基于从 DIC 获得的局部应变数据的空间平均的统计算法来确定的。有趣的是，发现微观和宏观变形之间的转变是材料密度的函数，但与施加的全局应变和应力无关。目前的结果为通过计算方法确定的细胞固体中的代表性体积元 (RVE) 大小提供了直接验证。