A new criterion, the limit stress, is presented for characterizing the mechanical performance of carbon fibers via the impregnated tow method. A description of the method and its underlying connection to actual single carbon fiber mechanical performance is given and an initial demonstration of the technique is implemented. For implementation, a commercial 24k tow carbon fiber was interrogated mechanically, and prepared using two independent approaches, resulting in two cross-sectional geometries; flat (ribbon) and round. The average ultimate failure stress and average limit stress from round to flat were reduced by 5.76% and 16.8%, respectively. Hence, the limit stress approach is between 2–3x more sensitive to induced variations in tow performance compared to the peak load approach. This method gives critical insight to the nuances of carbon fiber performance, important to the understanding of fiber types (for example low-cost carbon fibers) and coupled fiber surface optimization.

提出了一种新的准则，极限应力，用于通过浸渍丝束法表征碳纤维的机械性能。给出了该方法的描述及其与实际单碳纤维机械性能的潜在联系，并对该技术进行了初步演示。为了实施，机械地询问了商用的24k丝束碳纤维，并使用两种独立的方法进行了制备，从而产生了两种横截面几何形状；扁平（色带）和圆形。从圆形到平坦的平均极限破坏应力和平均极限应力分别降低了5.76％和16.8％。因此，与峰值载荷方法相比，极限应力方法对牵引性能变化的敏感性要高出2-3倍。