Effect Of External Load On The Structure And Mechanical Properties Of CFRP Under Alternating Temperature And Humidity Field

Carbon fiber reinforced polymer(CFRP)with a small specific gravity,high strength,high modulus,high temperature resistance,fatigue resistance and chemical corrosion resistance as well as good performance and is widely used in spacecraft,primary and secondary stress components and features.Space for composites during the period of service will be affected by temperature,humidity and uv radiation all sorts of harsh environmental factors,such as the hot and humid environment is composite material performance degradation of one of the most important factor.Currently,carbon fiber reinforced composite material of damp and hot research mainly focused on the performance of a single wet,hot,or hot and humid conditions,and load and wet and heat cycle under bending load environment effect on the properties of carbon fiber reinforced composite materials research is less,so the carbon fiber reinforced composites in the wet and heat aging environment and the influence law of bending load on its mechanical performance is of great significance.This paper to explore different porosity of carbon fiber/epoxy lamin ated plate is in the high low temperature aging environment and loads under the action of the evolution of the mechanical properties,based on the materials during the moisture absorption and the internal stress state of service,to high and low temperatur e alternating T700 CF / 3234 ep accelerated aging wet and heat cycle test.By controlling the moulding pressure,and the preparation of three kinds of porosity were 0.04,0.08 and 0.11 of laminated plates,the three kinds of porosity of laminated plates to load,load load of maximum bending load of the laminated plates respectively 0,30%,40% and 30%,and then put it in high and low temperature environment simulation test box,study different cycle structure and mechanical properties of composite laminated plates,by using ABAQUS software,and the finite element simulation of mechanical performance,finally forecasts the laminated plates in the wet and heat cycle,bending load under the coupled action of single and service life.The results show that the pores of the laminated plates are located near the interface area between the rich resins and the layers.The same porosity laminated plates,with the increase of wet and heat cycle,the pore number increased obviously,the same porosity change is not obvious,very close to the pore,pore between will be connected together to form larger pore.After loading,the laminated plates are the exact opposite,and with the increase of additional load,the individual porosity increases obviously,and the increase of pore volume is not obvious.With the increase of high temperature and humidity cycle,both bending and tensile strength are decreasing.The greater the porosity,the greater the decrease in bending and tensile strength.The damage mechanism of the heat cycle is mainly the removal of the fiber and resin.Under the same impact energy,the pit depth of the laminated plate after the thermal aging is less than that of the laminated plate without the aging of the damp and heat.With the increase of impact energy,t he pit depth increases,from 7.5j to 10 J,the depth of pit depth of laminates will be mutated.With the increase of the humid heat cycle,the greater the porosity of the laminated plate with the greater the porosity.Loading 40% and 60% of laminated plates increased by 1.5% and 1.6% respectively during the 4-6 cycle.The higher the loading of the laminates,the higher the solidification degree of the laminates,and the higher the hardness,the more obvious the change of glass transition temperature,but the chemical structure of the laminated plate has not changed.With the increase of wet and heat aging period,the greater the porosity and bending load,bending and tensile strength decline,the greater the laminated plate delamination and fiber debonding ph enomenon more obvious,in 4 to 6 cycles,due to the secondary curing of the resin,40% load and 60% load of the laminated plate bending and tensile strength of leveling off.With the increase of the humid heat cycle,the pore rate has the same laminates,a nd the larger the bending load,the smaller the pit depth.In addition to the bending load,the larger the porosity,the larger the pit depth.Use ABAQUS software to simulate the bending,tensile and impact mechanical properties of simulated values fit well with the test results,and through each layer of laminated plate bending,tensile and impact mechanical properties of simulation,found that the laminated plate bending,tensile and impact of each layer mechanical properties change rule are symmetrical distribution,and the intensity of the two layers in the middle of the smallest.The life prediction results show that both the wet and thermal environment and the bending load have greatly reduced the service life of laminated plates...