The effects of porosity and external loading on hygrothermal tensile mechanical properties and interfacial failure mechanism of CFRP laminates were studied by high and low temperature alternating accelerated hygrothermal cyclical test and finite element simulation. 3 kinds of laminates with different porosities were prepared by controlling molding pressure. The load on specimen was 30%

40% and 60% of the maximum bending load of laminates

respectively. The results showed that the increase of porosity was the main reason leading to the sharp decrease of tensile properties of CFRP laminates after hot-humid aging. The greater the porosity was

the more hygrothermal tensile strength decreased. The external load could accelerate the debonding of the interface between fibers and resin matrix

further degraded the hygrothermal tensile strength of the composites

and had different effects on the laminates with different porosity. Among of them

the most influential one was the laminate with porosity of 0.08

the second was the laminate with porosity of 0.04

and the least was the laminate with porosity of 0.11. And the greater the load

the greater the impact

but the influence of load on the hygrothermal tensile properties of the laminates was far less than that of the porosity. ABAQUS software was employed to simulate tensile properties of composite specimen. The tensile stress distribution of the laminates was investigated

and it was found that the tensile stress increased at 90 degree layer due to the hydrothermal cycle. Therefore

the matrix cracking and fiber/matrix interface debonding were prone to occur

resulting in the decrease of mechanical properties

which was consistent with the experimental results. The variation trend of tensile mechanical strength calculated by the ABAQUS software was consistent with the experimental results. Keywords: CFRP; porosity; bending load; hygrothermal environment; mechanical properties 〖FQ(+25mm。22

ZX-W〗收稿日期: 2017-12-20 基金项目: 黑龙江省自然科学基金（E201311） 作者简介: 张东兴(1961—)

男

教授; 贾近（1976—）

女

高级工程师通信作者: 贾近

jiajin@hit.edu.cn 碳纤维增强聚合物基复合材料（简称CFRP）具有比重小、比强度高、比模量高、耐高温、抗疲劳及耐化学腐蚀性能好等优点而广泛应用于飞行器的主、次受力构件及特殊部位的功能件[1-3]. 飞行器用复合材料在运输、贮存、发射或飞行过程中要面临如温度、湿度、复杂的外载荷等特殊环境

这些环境因子以不同的机制作用于复合材料

造成其降质退化直至损坏变质[4-9]. 例如

在超音速飞机飞行时

所用的复合材料要承受长期的温度在-55~130℃与湿度在0~80%RH交变的环境

经历多次飞行循环结束后

飞机进入维修护理期

在超音速飞机整个飞行服役期间

复合材料处于温度与湿度交变的湿热循环中[10-13]. 并且

由于CFRP制备工艺的特殊性

通常会形成孔隙、夹杂、分层等制造缺陷

其中

孔隙是复合材料结构中最为常见的缺陷之一. 大量的研究表明

孔隙会使CFRP在服役期间

因湿热等环境因素而加速材料性能的退化[14-16]. 目前国内外大多数学者多采用水浸、湿热试验箱等简单的恒温恒湿加速试验方法研究复合材料的湿热性能

试验湿热环境没有真实体现飞行器实际服役环境

同时未考虑外载荷的影响

得到的试验结果在实际应用上具有很大的局限性[17-19]. 因此

本文以含孔隙的碳纤维增强环氧树脂基复合材料(CF/EP)层合板为研究对象

基于材料服役期间的吸湿状态和内应力状态

通过模拟超音速飞机服役环境的高低温交变加速湿热循环试验

并结合有限元分析方法

研究湿热交变环境下孔隙率和外加载荷对CFRP层合板拉伸力学性能及界面破坏机理的影响

为CFRP在先进飞机中的应用提供理论设计依据. 1试验