纖維複合材料之位移觀點破壞判準

A Displacement-based Criterion for Fracture Analysis of Fibrous Composites

鄭榮和(Jung-Ho Cheng) ； 張朝萬(Chao-Wang Chang)

《中國航空太空學會學刊》 31卷2期 (1999/06) Pp. 91-100

https://doi.org/10.6124/TAASRC.199906_31(2).03

摘要

本文以位移爲觀點，提出一新的適用於纖維強化複合材料的破壞判準。判準中，只要由纖維角度0°及90°之破壞模式Ⅰ實驗，並透過有限元素輔助模擬分析，即可求得所需的破壞指標－臨界裂縫張開位移量。過程直接、簡單，且判準容易使用，能快速預測含裂縫纖維複合材料之破壞外力。
首先，在固定裂縫長度下，針對單一方向不同纖維角度之積層板進行驗證，發現可以精確預測破壞應力，再探討纖維角度30°不同裂縫長度之積層板的破壞應力仍得到相當準確結果，在考慮不同加載情形與裂縫形式影響下，設計雙裂縫試片試驗與四點彎曲試驗，結果顯示有不錯的準確度。由於複合材料應用時多以交錯疊層堆疊，本研究另行發展一套交錯疊層積層板的臨界張開位移量計算公式，進而用在積層板的破壞預測，有相當不錯的成果。
最後將本研究所推導的判準以及分析程式應用於壓力容器的破壞預測，結果顯示能很有效且準確地應用於大型結構物的破壞分析。經由許多驗證，可以確認本文所提出位移觀點之破壞判準能夠精確且簡易的應用於含裂縫按合材料結構的破壞分析。

關鍵字

破壞判準 ； 裂縫張開位移量 ； 單一方向積層板 ； 交錯疊層積層板 ； 有限元素法 ； 破壞力學

並列摘要

This paper proposes a new displacement-based fracture criterion valid for fiber reinforced composites. In this criterion, the required fracture parameter (critical crack tip opening displacement) can be obtained just from the Mode Ⅰ fracture experiments of 0 and 90 degrees unidirectional composites with the aid of finite element analysis. This criterion is simple, straightforward and easy to apply. The fracture load of fiber reinforced composites with crack can be predicted quickly.
First of all, the prediction ability of the criterion was verified by different methods. The fracture characteristics of the unidirectional composites are the basic property that controls continuous fiber reinforced composites, so some fracture experiments and finite element analysis were performed in this field, including double-edged specimen experiments, four point bending experiments and standard compact tension specimen experiments. From the results of verification the fracture criterion proposed in this paper can predict not only the failure of composites with different crack lengths but also the failure of the composite with different fiber directions.
After understanding the fracture characteristics of unidirectional composites, another formula was proposed to compute the critical crack tip opening displacement of laminate from the physical relations between lamina and laminate. It is successful in predicting the failure of laminate.
Finally, the criterion and finite element program were applied to predict the failure of a pressure vessel. The result shows that the process proposed by this paper can be applied effectively and accurately in the analyses of larges structures.