Thermomechanical analysis of micromechanical formation of residual stresses and initial matrix failure in CFRP
Thermomechanical analysis of micromechanical formation of residual stresses and initial matrix failure in CFRP
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DOI：
10.1299/jsmea.47.349
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发表时间：
2004-07-01
期刊：
影响因子：
--
通讯作者：
Schulte, K
中科院分区：
文献类型：
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作者：
Hobbiebrunken, T;Hojo, M;Schulte, K
采用有限元方法研究了单向碳纤维布的过程热残余应力和基体破坏。选取了由纤维微观区域和基体被均匀区域包围的部分离散模型复合材料。研究了关于残余应力形成和初始基体破坏的四种情况：自由ud -层压板，约束ud -层压板，交叉层压板和在冷却过程中遭受温度梯度的厚层压板。在对纯树脂进行热力学试验的基础上，建立了基于温度的基体应力-应变行为和抛物线破坏准则，并将其引入到有限元程序中。在不同的边界条件下，微观水平上的实际应力状态可以被描述出来。结果表明，在考虑细观力学效应的情况下，采用部分离散模型的方法确定不同宏观试样的初始基体破坏是合适的。结果表明：约束层合板和交叉层合板存在较高的三轴应力，导致90度层合板初始基体破坏；考虑温度梯度会影响基体中的应力分布，但对最大残余应力值的影响较小。在这种情况下，可以排除初始矩阵失效。
Process induced thermal residual stresses and matrix failure of unidirectional CFRP has been investigated by finite element methods. Partial discrete model composites consisting of a microscopic area of fibers and matrix surrounded by a homogeneous area were chosen. Four cases have been investigated concerning the formation of residual stresses and initial matrix failure: A free UD-laminate, a constrained UD-laminate, a cross ply laminate and a thick laminate which is subjected to a temperature gradient during cooling down. On the basis of experimental results from thermo-mechanical tests of the neat resin, the temperature dependent matrix stress-strain behavior as well as the parabolic failure criterion were formulated and introduced into the finite element program. The actual stress state on the microscopic level depending on different boundary condition could be described. The authors showed that the approach of a partial discrete model is suitable to determine the initial matrix failure of different macroscopic specimens under consideration of micro-mechanical effects. The results showed that high tri-axial stresses occur in the constrained laminate and the cross ply laminate, which lead to initial matrix failure in the 90degrees-ply. The consideration of a temperature gradient affects the stress distribution in the matrix though the influence on the maximum residual stress values is small. In this case, initial matrix failure can be excluded.