The Experimental Study Of Mechnical Properties Of MWCNTs/PA66Composites Under Impact Loading

Nylon66(PA66) as a most popular engineering plastics, has highmechanical strength, high softening point, heat resistance and it can alsomaintain strong strength and stiffness at high temperature. These excellentperformance makes it particularly suitable to be widely used in aerospace,sporting goods, automotive, weapons, constructions, daily necessities andmany other fields. PA66occupies the primacy positions of engineering plastics.However there are amide groups (-NHCO-) belongs to the polar groups in thestructure of PA66. When these groups are at high temperature, hot and damp orultraviolet radiation environment, they are largely easy to prone to thermaldegradation, hydrolysis degradation and light degradation, thus affectingdimensional stability and mechanical properties of products by PA66, reducingthe stability and service life of the products, this greatly limits the applicationof PA66.In order to overcome these shortcomings of the PA66, as well as expandtheir applied fields, the modification of PA66are necessary. According toprevious studies we find that adding multi-walled carbon nanotubes(MWCNTs) in PA66to prepare MWCNTs/PA66composites is a very effectivemethod. And it is also found that most of the studies of MWCNTs/PA66composites were focused on the crystallization properties, electrical properties, the static tensile properties. However, the role of real-life objects are oftensubjected to compression and impact, MWCNTs/PA66composites underimpact and compressive loads are rarely reported. Therefore, in this paper weprepared a series of MWCNTs/PA66composites with surface-modifiedMWCNTs and PA66by melt blending method. And we explored themechanical response of composites under quasi-static and dynamic conditions,by comparing the dynamic and static mechanical properties, the effects ofcontent of carbon nanotubes on the mechanical properties of MWCNTs/PA66composites were studied. The main results were as follows:(1) Adding A-MWCNTs makes MWCNTs/PA66composites ofcompression modulus, compression strength, significantly lower than that ofPA66; with the increase of P-MWCNTs and D-MWCNTs content, the elasticmodulus and the strength of the composite materials gradually increase, butwhen the content of P-MWCNTs and D-MWCNTs are more than2.5%, theelastic modulus and strength will gradually decline, even lower than PA66.(2) The yield strength of D25and P25are15.0%and13.2%larger thanthat of pure PA66respectively. When the MWCNTs content is more than2.5wt%, the yield strength of MWCNTs/PA66composites will decline.(3) MWCNTs/PA66and PA66composites have significant strain rateeffect, they are strain-rate sensitive material.(4) When the strain rate is same, compared with PA66, the performance ofP25and D25has improved significantly. For example, the maximumincremental compressive yield strength is of4%-13%. Compared with PA66,with the increase of MWCNTs wt%, the strength of the composites increasedfirstly and then decreased, the critical wt%is2.5wt%.