橡胶增韧高聚物的动态断裂

采用冲击改性的高聚物对材料的断裂能在近瑞利波速Cr时减小的断裂行为进行了研究.设计了基于条带几何形状的实验装置用以探索这些高聚物在快速裂纹传播(RCP)时的脆性行为.发现沿着橡胶增韧聚甲基丙烯酸甲酯(RT-PMMA)的整个试样,尽管有的出现裂纹分叉甚至裂纹俘获静止,其宏观裂纹速度几乎恒定.当材料行为趋于加速裂纹时,临近Cr时断裂能减少,而当由于分叉使力学惯性效应趋于限制裂纹传播速率时,宏观裂纹速度稳定在大约αmb=0.6Cr,其是RT-PMMA的宏观裂纹分叉速度.因此,对这种材料在宏观裂纹分叉速度时,实验断裂表面能及断裂表面韧性没有单一值.实际上,其宏观断裂表面能值随着失稳形态数目或无效裂纹分叉而增加.

Dynamic Fracture of Rubber Toughened Polymers

The fracture behaviour of materials for which the fracture energy decreases near the Raleigh wave; speed, cr, is investigated using an impact modified polymer. An experimental device based on strip band geometry has been designed to explore the brittle behaviour of such polymers during rapid crack propagation ( RCP) . The macroscopic crack speed is found to be quasi-constant along an entire rubber toughened polymethyl-methacrylate (RT-PMMA) specimen, even in the case of crack branching and until arrest. As the material behaviour tends to accelerate the crack, the fracture energy decreases near cr, whereas mechanical inertial effects tend to limit the rate of crack propagation-due to crack branching, the macroscopic crack speed stabilizes at approximately amb =0.6 cr, which is the macroscopic crack branching speed for RT-PMMA. Consequently, at the macroscopic crack branching velocity, the experimental fracture surface energy and the fracture surface roughness; have no single value in such materials. In fact, the macroscopic fracture surface energy value increases with the number of instabilities or frustrated micro-branches.