预混料吸湿对复合材料内部质量的影响

Effect of Moisture Absorbed Pre-mixture on Internal Quality of Composite Material

在RH85%的环境下,将高硅氧/酚醛预混料吸湿24 h后压制成复合材料,对试样进行无损检测和力学性能分析。结果表明:预混料吸湿后其复合材料内部存在大量缺陷,其中Ⅱ类区面积37.4%,Ⅲ类区面积49.8%;力学性能下降幅度较大,拉伸强度、压缩强度、冲压剪切强度分别下降了55%、60%、15%,但弯曲强度变化较小。分析表明:预混料吸湿的水分一部分在树脂固化时,成为气孔,形成Ⅱ类区;另一部分进入纤维,削弱树脂和纤维界面间的粘接力,严重时出现脱粘,形成Ⅲ类区,降低材料力学性能。

By exposing high silica/phenolic premix at a relative humidly(RH)of 85%for 24 h,the composite was prepared by hot pressing the premix,and then it was evaluated by non-destructive testing and mechanical property measurement.Experimental results show that there are a large amount of internal defect in composite materials,including 37.4% Class Ⅱ region and 49.8% Class Ⅲ region.In addition,mechanical properties of the composite decrease dramatically,showing 55% decrease in tensile strength,60% decrease in compressive strength and 15% decrease in shear strength.The formation of the internal defects can be mainly ascribe to two aspects:(1)The volatilization of part of water absorption in the premix forms pores in the composite during the curing process,forming Class Ⅱ region;(2)The rest water absorption by fiber weakens the interfacial adhesion between fiber and resin matrix and causes the debonding of the interface in serious conditions,resulting in the formation of the Class Ⅲ region.These reasons lead to decreased mechanical properties of composite.