Performance Study On Glass Fiber Reinforced Polypropylene Laminated Self-Reinforced Polypropylene Composites

With the advantages of low cost and good rigidity,Glass fiber reinforced polymer(GFRP) occupies a significant markets of communication base station covers,wind blades and so on.However,the toughness of GFRP is poor,its impact damage response is catastrophic structural failure.Under similar damage,the energy absorption is much lower than that of ductile materials.Many applications of GFRP,especially in the base station covers,are often threatened by natural impacts such as hail.Take the base station cover as an example,as the communication technology is upgraded to 5G,the base stations number required for 5G full coverage will be more than double of 4G,the manufacturing and maintenance costs will increase significantly.To use 4G GFRP covers will obviously bring challenges to the low-cost coverage of 5G.Self-reinforced polypropylene composites(SRPP)are new materials which has the advantages of low-cost,high-performance,completely recyclable.Excellent impact toughness is its mainly feature.With this advantage,SRPP has applied in the high-end market of luggage,protection fields.However,the relatively weak rigidity makes SRPP unable to bear the demand of structural stability on some occasions alone.In this paper,SRPP is introduced into glass fiber reinforced polypropylene composites(GRPP)in the form of laminated composites to obtain a new material with good toughness and rigidity,which provides a low-cost and high-performance choice for 5G low-cost coverage.In this paper,the effects of different structural parameters on the performance of laminates were studied.The main contents and conclusions are as follows:(1)Through tensile,flexural,compression,shearing and drop weight impact tests,static and dynamic mechanical performance of SRPP and GRPP were tested and characterized.Results show that there are fundamental differences in the tensile,flexural and impact mechanical performance of basic materials.The tensile strength and modulus of GRPP are 282.7 MPa and 13.85GPa,respectively,the tensile strength(115.4 MPa)and modulus(2.87 GPa)of SRPP are 40.8%and20.7%of GRPP,respectively.The break elongation of SRPP has reached 27.79%,GRPP(1.97%)is only 7.1%of SRPP.The flexural modulus of GRPP is 10.63 GPa,SRPP(1.78 GPa)is only 16.7%of GRPP,but SRPP has strong flexural resistance,there is no damage until high strain.GRPP has been severely damaged under the impact energy of 6 J/(kg/m~2),SRPP has no penetration under 50J/(kg/m~2).Taking GRPP as reference,the best impact energy level is determined as 5 J/(kg/m~2).Two basic materials have obvious characteristics and great differences,which can play a significant complementary role.(2)Based on several research and theoretical model,the structural configuration is as follows:1.Centralized paving;2.Set three thickness ratio of SG1∶1,SG1∶2 and SG1∶3;3.Set two position structures,S/G/S and G/S/G.Laminates were prepared by vacuum bag pressing technology.The actual thickness ratio difference with expected value was within 2%,the combination of basic materials was excellent,which met the expected quality requirements.(3)In the tensile performance of laminates,the greater the GRPP thickness ratio,the greater the tensile strength and modulus.The strength improve is not obvious as modulus,the maximum strength is 186 MPa of G/S/G-SG1∶3,which is 62%higher than SRPP.The maximum modulus is 10.21GPa of S/G/S-SG1∶3,which is 256%higher than SRPP.S/G/S tensile strength is lower than G/S/G,the maximum strength of two structures is 145.37 MPa and 186.49 MPa respectively.But S/G/S tensile modulus is higher than G/S/G,the maximum modulus of two structures is 10.21 GPa and 9.45 GPa respectively.In terms of toughness,the greater the GRPP thickness ratio,the greater the failure strain(all higher than GRPP),since the hybrid synergistic effect will become stronger as the hybrid ratio transitions from 50%to two extreme values(0%,100%).The SRPP skin thickness on both sides of S/G/S is half of SRPP core in G/S/G,so the toughness of SRPP skin weaker,which makes the overall failure strain of S/G/S lower than G/S/G.(4)In the flexural performance of laminates,the flexural stress prediction model of laminate structures is proposed based on the elementary beam theory,which basically consistent with the experimental results.The flexural response of G/S/G is similar to GRPP,it is a kind of buckling failure with relatively high flexural strength and modulus.The strength of G/S/G-SG1∶3is 203 MPa,which is 98%of GRPP,and the modulus is 11.77 GPa,which is higher than GRPP.The flexural response of S/G/S is similar to SRPP,its flexural resistance is relatively strong,SG1∶1and 1∶2 are not obviously damaged.In terms of toughness,S/G/S is very strong,the failure strain of G/S/G is slightly lower than GRPP,but it will increase with the increase of SG ratio.(5)In the impact performance of laminates,for low energy,the greater the GRPP thickness ratio,the smaller the peak load,energy absorption and displacement.S/G/S impact response is similar to GRPP,with low peak load which demonstrate as platform,and low proportion of elastic potential energy in energy absorption;G/S/G is similar to SRPP,with high and sharp peak load,and high proportion of elastic potential energy in energy absorption.Different from their similar basic materials,S/G/S has higher energy absorption and displacement than G/S/G.The characterization of depth dimension based on DIC proves that S/G/S has higher deformation than G/S/G except the crack generation and propagation similar to GRPP,but it is mainly rigid failure deformation.(6)On the dielectric performance,structural factors have no obvious influence.In the 5G normally frequency band of 2.5～5 GHz,the dielectric constant of each laminate is lower than 4,the electromagnetic wave transmittance is higher than 80%,which shows good electromagnetic wave permeability.