碳纤维复合材料内部缺陷深度的定量红外检测

利用脉冲红外热成像技术对碳纤维复合材料试件内部的模拟脱黏缺陷的深度进行测量, 研究在被测物热属性参数未知情况下,碳纤维增强塑料中缺陷深度的测量方法. 分析了平板材料在脉冲热源激励下的一维热传导模型;给出了内部缺陷深度的红外测量原理; 选用对数温度二阶微分峰值时刻作为特征时间测量缺陷深度; 考虑单点标定测量深度可能产生较大的随机误差,提出利用最小二乘法多项式拟合建立阶梯件中阶梯深度与其对应的对数温度时间二阶微分曲线峰值时间两者之间的标定关系式的方法, 选择在相对误差平方和最小情形下的拟合关系式作为脱黏缺陷深度测量的标定关系式. 实验结果表明,利用该方法测量脱黏缺陷深度的精度优于单点法标定测量结果, 实现了在被检测材料热属性参数未知的情况下仍能较准确地测量脱黏缺陷深度.

Quantitative infrared prediction method for defect depth in carbon fiber reinforced plastics composite

In this work, we present a quantitative method of predicting defect depth within carbon fiber reinforced plastics (CFRP) composite with unknown thermal property of specimen. The method discussed in this paper is derived from theoretical model of ideal one-dimensional heat conduction in a flat plate sample. The principle of depth prediction using pulsed infrared thermography is presented; the time based on the peak second-derivative of the temperature difference in the logarithmic scale is selected as the characteristic time; the calibration curve based on data of single defect depth can be easily affected by random error. The calibration curve is put forward in the paper and obtained by designing a stepped reference sample, and it can be obtained by a curve fit of different depths and corresponding characteristic time using polynomial function. The polyfitting curve is used as the calibration curve for depth prediction when the relative error square is minimum. The experimental results show that the depth measured by the calibration curve based on many reference defect depths is more accurate than by single reference defect depth. Defect depth in CFRP composite can be measured by the method without knowing thermal property of specimen.