共聚聚丙烯材料的断裂行为

FRACTURE BEHAVIOUR OF CO-POLYPROPYLENE

采用基本断裂功方法(EWF)评价了四种不同牌号共聚聚丙烯材料的断裂韧性和塑性功,并结合材料的热性能及力学性能进行了分析。研究发现,EWF方法比常规力学性能可更有效地揭示材料长期破坏行为的特征。各种共聚聚丙烯的比非基本断裂功βwp相差不太大,但长期断裂破坏行为较好的材料(A和B)的比基本断裂功we相对较大,说明它们在断裂过程中抵抗裂纹扩展的能力较强;而且其屈服前与屈服后的比基本断裂功we,y,we,n都比较大;长期断裂破坏行为较差的材料C的we,y,we,n均很低,而材料D的we,n虽较高,但we,y较小,这可能与材料的晶粒数量和大小有关。

The essential work of fracture (EWF) method was employed to determine the fracture toughness of four types of co-polypropylene, while the thermal properties and mechanical properties of the materials were analyzed. It is found that it is available for the EWF method more than yield strength and impact strength to characterize the materials′ service behavior under stress during long time. The values of β w_p, the energy dissipated in the plastic deformation, of the four materials have no much difference. But w__e values, the resistance to crack propagation, of the materials A and B which are not easy to fracture during long service time are higher w__(e,y) values, the resistance to fracture before yielding, of A and B are higher, and w__(e,n) values of them are also relatively higher, which is a possible reason for their better service behavior under low stress. However, w__(e,y) and w__(e,n) values of material C which tend to fracture during long service time are much lower. w__(e,y) value of material D is lower though w__(e,n) value of it is relatively higher, that maybe dependent on the amount and size of crystal grains in the materials.