树脂基体的韧性对复合材料力学性能的影响

 以双酚A型环氧树脂——无规羧基丁腈橡胶——2-乙基-4-甲基咪唑体系为代表,考察了树脂基体的韧性对单向玻璃纤维复合材料力学性能的影响。试验结果表明:随着树脂基体韧性的提高,所得复合材料的伉断裂性能相应地增加,但提高的幅度较树脂基体本身韧性的提高值小;复合材料的短梁剪切强度、除拉伸模量以外的横向力学性能也随树脂基体韧性的增加而提高,而弯曲性能及纵向力学性能受树脂基体韧性的影响不明显。

TOUGHENING EPOXY RESIN MATRIX FOR GLASS AND CARBON FIBRE COMPOSITES——EFFECTS OF MATRIX TOUGHNESS ON THE MECHANICAL PROPERTIES OF FIBRE COMPOSITES

How to toughen an epoxy resin system for glass and carbon fiber composites is investigated.The system consists of butadiene-acrylonitrile rubber with random carboxyl groups（CTBNX）,epoxy resin of diglycidyl ether of biphenol A（DGEBA）and 2-ethyl-4-methylimidazol.The main objectives of this research are:（1）to toughen epoxy resins with commercially available elastomer CTBNX;and（2）to determine the effectiveness of this CTBNX-modified epoxy resin system in fiber reinforced composites.The authors'previous studies（4,5）show that the toughened epoxy resin can be prepared with CTBNX or CTBNX-bisphenol A to form a two-phase system.The toughened epoxy resins exhibit significant improvements over the unmodified ones in impact strength,modulus of toughness（area under the stress- strain curve）and fracture surface energy,by as much as 2 to 10 times,0.5 to 11.5 times and 1 to 4 times respectively.This paper presents the research results of the effects of matrix toughness on the crack resistance,impact strength and mechanical properties of unidirectional glass fiber composites and describes the technique of measuring the fracture toughness KQ of fiber composites.Test results show that:1.In the unidirectional glass epoxy composites,the increases of transverse and longitudinal impact strengths,fracture surface energy and candidate stress intensity factor KQ depend mainly on enhancement of the resin matrix toughness,but are not so large as in bulk resins and only modest,though still the increases obtained are significant.Wtih enhancing the matrix toughness,short beam interlaminar shear strength and all transverse mechanical properties except tensile modulus of composites increase,while all longitudinal mechanical properties and flexural properties change inappreciably.2.The use of double edge notched tension specimen（DEN）for determining fracture toughness of unidirectional fiber composites is recommended.