Investigation On Hydrothermal Aging Behavior Of Carbon Fiber Reinforced Nylon-6 (CF/PA6) Laminates

Continuous carbon fiber reinforced thermoplastic resin nylon-6?CF/PA6?composites have attracted more and more attention in the engineering field because of its high specific strength,high specific modulus,wear resistance and easy recovery.However,the strong hygroscopicity of nylon-6 limits its application in automotive industry and other fields.Therefore,it is of practical significance to study the moisture uptake behavior of CF/PA6composites in hydrothermal environment.In addition,according to the characteristics of nylon-6 and carbon fiber,the effect of modification of matrix and reinforcement onmoisture resistance and mechanical durability were studied.The main contents of this paper are as follows:Firstly,CF/PA6 composite laminates were prepared by a laminating method.The hygroscopicity and the service performance of the composites were tested.The moisture uptake and mechanical properties of CF/PA6 composite laminates under hydrothermal environment were investigated.According to the moisture absorption curve obtained from the experiment,the mathematical model was established,and the moisture absorption behavior of CF/PA6material was proposed with a novel extended Fickian model to capature the post-saturation diffusion behavior,which could describe the moisture absorption process of the material in thermal hot/wet environment.The relationship between service performance and aging time of CF/PA6 laminates were analyzed,and the degradation of service performance is related to the moisture absorption rate of materials.A mathematical model of mechanical retention is established to describe the degradation of mechanical property..Secondly,talc powder was used to modified nylon-6 matrix.The moisture uptake of CF/PA6_t composites were tested and the service performance was monitored.The experimental results showed that the addition of talc powder enhanced the moisture resistance of the composites.The cross-section of the composites before and after aging are observed by metallographic microscope and scanning electron microscope.The influence mechanism of talc powder on the aging process was analyzed.The results showed that talc powder inhibited the diffusion of water molecules into the composites,thus improving the moisture resistance of the composites.In addition,the content of talc powder was compared and optimized.10 wt%talc powder reduced the mechanical properties of the materials.On the other hand,carbon nanotubes?CNT?were grafted onto carbon fibers woven fabric to improve the interfacial adhesion between matrix and fibers The grafting of CNT onto carbon fibers were confirmed by means of infrared spectroscopy and X-ray photoelectron spectroscopy.The hydrothermal aging experiments of the modified CF_CNT/PA6 composites were carried out.The results showed that the moisture resistance of the CF_CNT/PA6 composites has been greatly improved during aging under 60^oC environment.The reason was ascribed that the grafting modification of carbon fibers by CNT enhanced the interfacial bonding between the fibers and the matrix in the composites,which reduced the cracks and debonding of interface caused by the erosion at higher temperature.In addition,the mechanical properties of CNT grafted CF/PA6 materials have been greatly improved,and the flexural strength and modulus have been increased by about 10%.Therefore,CNT grafting of carbon fiber woven fabric contribute to an improvement in the mechanical properties of CF/PA6 composites and their moisture resistance under hydrothermal condition.This study provides data support and theoretical guidance for the research and application of CF/PA6 composites under hydrothermal condition.