The Study On Notched Strength Of Glass Fiber Reinforced Thermoplastic Composites

In recent years,with the development of fiber reinforced plastic(FRP)molding technology,they are widely used in the automotive industry due to its high strength and stiffness,high corrosion resistance,good fatigue resistance.In the composition of the car,the application of FRP composites covers the structure of the car and semi-structural parts,Auto parts need to be drilled in the assembly process.So the notched strength of composite materials is an important property that has gained extensive use by designers.Many researchers have devoted themselves to investigating the effects of different factors on notched strength.In the study,non-alkali glass fiber(GF)as the reinforcement,polypropylene(PP),POM(POM),polycarbonate(PC),polyamide(PA)resin as the matrix respectively,were used to produce Four different types of glass fiber reinforced composites by injection molding Methods,and each of which had two different fiber contents.The influence of the hole on the tensile properties of the composites was investigated by the tensile test of eight kinds of composites.The effects of hydrothermal aging and low cycle tensile fatigue on the composite materials were studied.In addition to the study of mechanical properties,The interfacial bonding of the composites and the interface between the fibers and the resin were also investigated by scanning electron microscopy(SEM).Conclusions from the above experiment were as follows: 1)Compared with the tensile strength of glass fiber reinforced composites,GF / PA composites have the best tensile properties,while the tensile properties of GF / PA composites are the worst.2)Opening holes had little effect on the tensile properties of GF / PP composites,While had a significant effect on the tensile properties of GF / POM,GF / PC,GF / PA composites.And the effect of opening hole on the composite material increases with the increase of fiber mass content.3)The sensitivity of four composites on the opening holes was investigated by finite element simulation.According to the results,GF / PA composites were the most sensitive to the opening holes,which was similar to the tensile test results.4)In terms of GF / PP composites and GF / PC composites,the water absorption and weight loss rate did not change significantly as the immersion time increased,in terms of GF / POM composites and GF / PA composites,the water absorption and the weight loss rate increased as the immersion time increased.5)Tensile tests on immersed specimens are carried out to investigate the degradation of eight kinds of composites.The results showed that when the glass fiber mass fraction is 10%,the notched strength of GF / PP composites hardly changes after hydrothermal aging.While the notched strength of other seven composites decreased more than 10% after hydrothermal aging,so that damp-heat aging had a significant effect on other seven composites.6)In the LCTF test,it was shown that 55% pre-set load low cycle tensile fatigue(LCTF)had no significance influence on eight kinds of composites.70% pre-set load LCTF had a significant effect on GF / POM-20% composites and GF / PA-40% composites,but had no significant effect on the other six composites.However,eight kinds of composites don't go through more than 85% pre-set load LCTF tests,because the eight kinds of samples were broken in the LCTF.