Background

The tensile strength along the longitudinal direction of unidirectional carbon fiber reinforced plastics (CFRPs) constitutes important data for the reliable design of CFRP structures. Our earlier reports proposed the formulations for the statistical static, creep, and fatigue strengths of CFRP based on Christensen’s model of the viscoelastic crack kinetics.

Objective

This study is concerned with the statistical assessment of the tensile static, creep, and fatigue strengths of unidirectional CFRPs by using the proposed formulations and the characterization of the long-term strengths of unidirectional CFRPs.

Method

First, the proposed formulations for the time-dependent and temperature-dependent statistical static, creep, and fatigue strengths of CFRP are introduced. Second, the tensile static, creep and fatigue strengths of unidirectional CFRP are measured statistically at various temperatures using resin-impregnated CFRP strands as tensile test specimens by measuring the viscoelasticity of the matrix resin. Finally, the master curves showing the long-term life of these strengths are constructed by substituting these measured data into the formulations.

Results

The results clarify that the formulations are applicable with high reliability over wide ranges of time and temperature for the statistical tensile static, creep and fatigue strengths of unidirectional CFRP except above the glass transition temperature of the matrix resin. Therefore, the fatigue strength degradation phenomena of unidirectional CFRPs can be expressed by the time- and temperature-dependent part due to the viscoelastic behavior of the matrix resin and the number of load cycle-dependent parts.

Conclusions

The long-term life prediction of unidirectional CFRPs under static, creep and fatigue tension loadings can be determined by ascertaining the mechanical properties of the CFRP and matrix resin in the proposed formulations.

中文翻译：

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单向CFRP拉伸静态，蠕变和疲劳强度的统计评估

背景

单向碳纤维增强塑料（CFRP）沿纵向的拉伸强度构成了CFRP结构可靠设计的重要数据。我们的早期报告根据Christensen的粘弹性裂纹动力学模型，提出了CFRP的统计静态强度，蠕变强度和疲劳强度的公式。

客观的

这项研究涉及通过使用建议的公式对单向CFRP的拉伸静态，蠕变和疲劳强度进行统计评估，以及对单向CFRP的长期强度进行表征。

方法

首先，介绍了针对CFRP随时间和温度变化的统计静态，蠕变和疲劳强度的建议公式。其次，使用树脂浸渍的CFRP股线作为拉伸测试样品，通过测量基质树脂的粘弹性，在不同温度下统计地测量单向CFRP的拉伸静态，蠕变和疲劳强度。最后，通过将这些测得的数据代入配方中，可以构建出显示这些强度的长期寿命的主曲线。

结果

结果表明，除了高于基质树脂的玻璃化转变温度以外，该配方还可以在宽范围的时间和温度范围内以高可靠性适用于单向CFRP的统计拉伸静态，蠕变和疲劳强度。因此，由于基体树脂的粘弹性行为和负荷循环相关部分的数量，单向CFRPs的疲劳强度降低现象可以由时间和温度相关的部分表示。

结论

通过确定拟议配方中的CFRP和基体树脂的机械性能，可以确定单向CFRP在静态，蠕变和疲劳张力载荷下的长期寿命预测。