Ductility and toughenability study of epoxy resins under multiaxial stress states
Ductility and toughenability study of epoxy resins under multiaxial stress states
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DOI：
10.1023/a:1013222421843
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发表时间：
1998-07-01
影响因子：
4.5
通讯作者：
Yee, AF
中科院分区：
文献类型：
--
作者：
Kishi, H;Shi, YB;Yee, AF
研究了未改性环氧树脂和橡胶改性环氧树脂在多轴应力状态下的局部应变。采用不同环氧单体分子量的环氧树脂，可改变基体的延展性。通过改变试样的厚度，使应力状态由1 × 1应变状态转变为平面应力状态。结果证实，在未改性树脂的情况下，经历近单轴拉应力的较薄试件在破坏时表现出比经历高三轴拉应力的较厚试件高得多的局部应变。交联密度随着单体分子量的增加而减小，因此应力状态变化引起的局部塑性应变的增加也随之增大。此外，研究发现，橡胶改性显著增加了破坏的塑性应变，而与试样尺寸无关，并且这种塑性应变的程度随着交联密度的降低而增加。这些结果与橡胶颗粒的空化解除了厚试样中初始多轴约束的概念是一致的，在整个试样中诱导出更接近平面应力的应力状态，从而使基体变形程度更大。结果还清楚地表明，基体树脂的增韧性与应力状态和基体塑性无关。(C) 1998 Kluwer学术出版社。
The local strains in unmodified and rubber-modified epoxies under multiaxial stress states were examined. Matrix ductility was varied by using epoxide resins of different epoxide monomer molecular weights. The stress state was altered from a pi a ne strain case to a plane stress case by varying the thickness of the test specimens. It was confirmed that, in the case of unmodified resins, the thinner specimens which experienced nearly uniaxial tensile stress exhibited much higher local strains at failure than the thicker counterparts which experienced highly triaxial tensile stress. Also, the cross-link density was reduced as monomer molecular weight increased, thus the increase in local plastic strain due to the stress state change also became greater. Furthermore, it was found that rubber modification markedly increased the plastic strain to failure, irrespective of the specimen dimensions, and that the extent of this plastic strain increased as cross-link density was lowered. These results are consistent with the concept that the cavitation of rubber particles relieves the initial multiaxial constraint in a thick specimen, induces a stress state closer to plane stress throughout the specimen, and consequently enables the matrix to deform to a larger extent. The results also show clearly that the toughenability of a matrix resin is not independent of the stress state and the matrix ductility. (C) 1998 Kluwer Academic Publishers.