The University of Tokyo

利用损伤力学分析方法，推导了与基质开裂有关的能量释放率和裂纹层的平均应力。基于能量准则和平均应力准则，预测了层合板应力对基体裂纹密度的影响。分析了层合板的应力和裂纹密度对层合板应变增量的影响，预测了考虑层合板开裂时层合板的应力应变关系。通过实验观察了层合板在静态拉伸载荷下的损伤过程，研究了层合板中树脂、铺层顺序和温度对层合板损伤的影响。对层合板的应力应变关系和基体裂纹行为进行了分析预测，并与实验结果进行了比较。对基体裂纹行为的分析预测与实验结果吻合较好。然而，分析预测低估了层合板的应力，因为在分析中高估了与基体裂纹张开位移相关的应变增量。该预测方法的优点是可以应用于具有任意堆叠顺序的层合板。此外，还观察了准各向同性CFRP层合板在疲劳拉伸载荷下的细观损伤演化行为。研究了堆积顺序对微观损伤的影响。采用损伤力学分析方法，推导出了与基体开裂相关的能量释放率。采用修正的巴黎定律模拟了复合材料的开裂行为，并研究了热疲劳载荷作用下正交层合板的细观损伤过程。基体裂纹在O°层和90°层均有萌生，且随着循环次数的增加，裂纹数目增多。结果表明，修正的Paris法适用于超薄层，平均应力法适用于厚层。

A damage mechanics analysis was used to derive the energy release rate associated with matrix cracking and average stress of cracked plies. Matrix crack density as function of laminate stress was predicted based on both energy and average stress criteria. Laminate strain increment caused by matrix cracking was also derived as a function of applied laminate stress and matrix crack density, and the relation between laminate stress and strain could be predicted considering matrix cracking.Microscopic damage progress under static tensile loading was observed to study the effect of matrix resin, stacking sequence and temperature, experimentally. The analytical prediction of matrix crack behavior and the relation between laminate stress and strain were compared with the experimental results obtained. Analytical predictions for matrix crack behavior were in good agreement with experimental results. However, analytical prediction underestimated the laminate stress, because strain increment associated with matrix crack opening displacement is overestimated in this analysis. An advantage of the present predictive method is that it can be applied to laminates with arbitrary stacking sequences.Microscopic damage progress behavior in quasi-isotropic CFRP laminates under fatigue tensile loading was also observed. The effect of stacking sequence on microscopic damages was investigated. Damage mechanics analysis was used to derive the energy release rate associated with matrix cracking. Matrix cracking behavior was modeled using modified Paris-law approach.Microscopic damage progress in cross-ply laminates under thermal fatigue loading was also investigated. Matrix cracks initiated in both O° and 90° plies and the number of cracks increased as the number of cycles increased. It was found that modified Paris law approach was effective far thin plies and average stress approach was effective for thick plies.