缝高比对FRP拉挤型材软化关系的影响

Influence of crack-height ratio on tensile softening relationship of pultruded FRP

为研究FRP拉挤型材拉伸软化特性,对顺纤维方向切口梁采用了三点弯曲试验,试件初始缝高比分别为0.2、0.3、0.4和0.5。试验测定了试件的荷载-挠度(P-δ)曲线、荷载-裂缝口张开位移(P-CMOD)曲线和荷载-裂缝尖端张开位移(P-CTOD)曲线,结果显示FRP拉挤型材断裂过程包括3个阶段:线性阶段、稳定阶段与失效阶段,表现为准脆性断裂破坏。应用P-δ曲线计算试件断裂能,再根据拉伸强度、断裂能以及变形关系建立双线性拉伸软化曲线。总断裂能由微裂纹断裂能和纤维桥连断裂能组成,研究表明:总断裂能大小不受初始缝高比影响,微裂断裂能约占总断裂能的60%;拉伸软化曲线受初始缝高比影响明显,建立了相应的函数公式。

In order to study the tensile softening property of puhruded FRP, a threepoint fracture test on single not- ched specimens was taken out along the fiber direction notch. The initial crack height ratioswere set as 0.2, 0.3, 0.4 and 0.5. The load-deflection （P - 8） curve, the load-crack mouth opening displacement （P - CMOD） curve, and the load-crack tip opening displacement （P - CTOD） curve were measured and recorded during the test. The result shows that, a quasi-brittle fracture phenomenon is obvious for pultruded FRP, which includes three stages： linear stage, stable stage and failure stage. According to the P -8 curve, the fracture energiesof tested specimen areealculated to obtain bilinear tensile softeningcurve. The fracture energy is composed of two parts, cracking frac- ture energy and fiber bridging fracture energy. It shows that the crack - height ratio has little effect on the fracture energy, and the cracking fracture energy takes about 60% of the total fracture energy. The tensile softening model is obviously influenced by the initial crack height ratio, while the function formula between model parameters and crack height ratio is built.