加捻z-pin与层合板的界面粘接性能试验

Experimental study on interfacial adhesive properties between twisted z-pin and laminates

通过小孔模具成型并在升温固化前对纤维束加捻的方法制备了5种捻度(捻度t分别为1、2、2.5、3和4 n/cm)的z-pin。观察了各种捻度z-pin的外观形态,测试了各种z-pin的拉伸性能。通过单根z-pin从层合板中拔出的试验方法表征了z-pin与层合板之间的界面粘结性能。结果表明,加捻使z-pin主干发生扭曲,捻度越大,扭曲的程度越大;加捻使zpin的拉伸强度及伸长率降低了50%左右,使拉伸模量降低了30%左右;加捻可显著提高z-pin与层合板之间的界面粘结性能,捻度越大,界面剪切强度τd、最大摩擦力Ff、拔出功Wp越大;随着捻度的增大,z-pin与层合板间脱粘位置逐渐从zpin自身的纤维与树脂之间的F-R型细观界面向z-pin外层树脂与层合板树脂之间的R-R型细观界面转移。当捻度t=3n/cm时,与无捻z-pin相比,τd提高了61%,Ff和Wp均提高了2倍。

Five types of twisted z-pins（ the twist degree are 1, 2, 2.5, 3 and 4 n/cm respectively） were prepared by means of draw forming from small-cavity mold and twisting before resin curing. Appearances of various twisted z-pins were observed, and the tensile properties of various twisted z-pins were tested. The interfacial adhesive properties between z-pins and laminates were charac-terized through single z-pin pull-out tests. The results show that twisting makes the stems of the z-pins distorted, the more twist de-gree is, the more distortion is. Twisting makes the tensile strength and the elongation reduce by about 50%, and the tensile modulus decreases by 30%. However, twisting improves the interfacial adhesive properties between z-pins and laminates significantly. The more the twist degree is, the higher the interfacial sheer strength τd, the maximum frictional force Ff, and the pull-out energy Wp are. With the increase of twist degree, the debonding location shifts from the F-R meso-interface between its fiber and resin of z-pin to the R-R meso-interface between the outer resin of z-pin and the resin of laminates. For the z-pin with twist degree of 3 n/cm, theτd is improved by 61%, Ff and Wp are all tripled.