The Effects Of Hygrothermal/High Temperature Environment On Low Velocity Impact Properties Of C/BMI Composites

In this paper,In this paper,T700/HT280 composite and its matrix resin were treated by hygrothermal(80?,85%RH)and high temperature(200?)environmental aging.The effects of hygrothermal and high temperature environmental aging on mechanical properties and low speed impact properties of T700/HT280 composite were analyzed by means of electronic balance,dynamic mechanical thermal analysis(DMA),ultrasonic C scanning and scanning electron microscopy.The results show that:The moisture absorption rate of resin and composite materials in hygrothermal environment is similar to the mass loss rate in high temperature environment,which increases rapidly first and then slowly increases and finally tends to be stable.The saturated moisture absorption rates of resin and composite materials are 3%and 1%in the hygrothermal environment,and the maximum mass loss rates are 1.3%and 0.6%in the high temperature environment.The quality change of composites affected by environmental aging mainly comes from the quality change of matrix resin.Hygrothermal and high temperature have a certain impact on the mechanical properties of materials.In the hygrothermal environment for a long time,the static mechanical properties of the material are lower than the original state due to the combined effect of wet stress,thermal stress and the entry of water molecules.In the high temperature environment of 200? for a long time,the material is affected by post-curing and physical aging,and the performance has an improvement trend in a short time.However,with the extension of time,aging dominates,and the performance decreases,which is lower than that of the original state.By testing the dynamic mechanical properties of the resin and composite before and after hygrothermal and high temperature aging treatment,it was found that hygrothermal had little effect on the Tg of the material,and the phenomenon of "peak deviation" appeared,which was attributed to the local interfacial debonding between the fiber and the resin.High temperature makes Tg increase,indicating that high temperature makes the material post-curing effect,increases the crosslinking density.Through visual observation and ultrasonic C-scan analysis of the impact damage of materials before and after environmental treatment,it can be seen that hygrothermal and high-temperature environment cause certain damage to materials,and the damage caused by high temperature is more serious.With the increase of impact energy,the impact absorption energy increases continuously.When the impact energy reaches 60J,the material will suffer from penetrating damage.The compressive strength of the composites after aging in hygrothermal and high temperature environment decreases with the increase of impact energy.Impact energy of 30J?40J can effectively characterize the damage effect of aging in high temperature and hygrothermal environment.Comparing the finite element simulation results with the actual damage results,it can be seen that the finite element model can well simulate and analyze the process and results of low velocity impact.