预报三向碳碳材料在简单拉伸时的切口强度的模型

MODELLING OF NOTCHED FAILLURE OF 3D CARBON CARBON UNDER SIMPLE TENSION

首先,一面加载,一面用偏光显微镜观察切口附近的先天缺欠的发展情况。为了跟踪切口尖端,设计了加载装置和可调台架。在观察基础上建立起一个非常简单的计算模型。为了用微结构力学来预报其切口强度,设计一个专用夹具来测量纤维束的强度。含切口的三向碳碳材料的强度实际上是切口附近应力集中发生的那一段纤维束的纵向强度所决定的。修正 Hedgepeth 的无限大板的应力集中系数。用 Zweben的统计强度准则作强度预报,与实验结果作比较。

First of all,the development of inherent damage near notch tip in 3D carbon carbon was examined with polariscopic microscope while loading. The notch tip was tracked With a specially designed adjustable stand and loading appratus during testing.Based on the observation,a very simple anaiytical model was established.In order to use micromechanics to pre- dict the notched strength,the strength of in-situ fiber bundle was mea- sured with a specially designed fixture.The strength of 3D carbon carbon is dominated by the longitudinal strength of the portion of fiber bundle, where the stress concentration takes place.Hedgepeth′s stress concentration factor for infinite plate is corrected for finite plate.Calculation of stress concentration factors of fiber bundles near notch tip also shows that fai- lure of a single fiber bundle will cause total rupture of the specimen.With Zweben's statical strength criterion,the strength of the notched 3D car- bon carbon was predicted and the prediction agrees with experimental resu- lts quite well.