碳纤维混凝土受弯断面的数字重构与断裂能计算

断裂能是定量表征混凝土断裂韧性的重要指标,但其实验结果显著依赖于混凝土试件断面面积评价方法的有效性和准确性。因测定困难,通常情况下只能由截面面积代替,造成断裂能计算结果存在较大误差。本文以碳纤维混凝土为研究对象,采用数字处理技术对混凝土断面形貌进行量化分析、重构,结合分形计算方法得到混凝土的真实断面面积,并将其用于碳纤维混凝土的断裂能计算,分析讨论了纤维掺量和长度对混凝土断裂能的影响规律。实验结果表明:碳纤维的引入显著提高了混凝土断面的粗糙度,表现为断裂面分形维度的明显提高,实际断面面积随之增大,以此为依据计算出的混凝土断裂能及其增益比随碳纤维掺量和长度的变化规律与韧度系数测试数据(按ASTM C1018)的一致性良好。

Digital Reconstruction of Bent Fracture Surface and Fracture Energy Calculation of Carbon Fiber Reinforced Concrete

Fracture energy is an important index to quantitatively characterize the fracture toughness of concrete. However, its experimental results are significantly dependent on the effectiveness and accuracy of concrete specimen fracture surface area. Because of the difficult to accurately measure the actual fracture surface area, it is usually replaced by its section area, which can result in large errors in fracture energy calculation. In this paper, taking carbon fiber reinforced concrete as study object, using digital processing technology, quantitative analysis of concrete specimen fracture surface morphology and its reconstruction were carried out. By combining with fractal calculation, the actual fracture surface area of carbon fiber reinforced concrete specimen was obtained, which was used in its fracture energy calculation. The influence of carben fiber content and length on concert fracture energy was discussed. Results show that the introduction of carbon fiber significantly improves fracture surface roughness: the fractal dimension of fracture surface is obviously increased and the actual fracture surface area increases therewith; based on which, the calculated concrete fracture energy and its gain ratio with the variation of carbon fiber content and length are in good accordance with measured data of toughness coefficient (according to C1018 ASTM).