Effect Of Heat Curing Process Of Resin And Heat Treatment Of Ramie Fiber On Resin Matrix Composites

The energy crisis and environmental problems have prompted people to widely develop plant fiber composite materials to partially replace chemical fiber in production and life applications.Ramie fiber has become a research hotspot because of its renewability,wide source,light weight,low cost,degradability,high specific strength and specific modulus,excellent comprehensive mechanical properties.However,it is easy to decompose at high temperature and has strong polarity,which affects the application of its composite materials.In this work,the effect of different pre-curing temperatures(130?-2 h,155?-2 h,180?-2 h)on the performance of phenolic resin and ramie fiber reinforced phenolic resin composite(RFRP)was studied.The thermomechanical analyzer(TMA)in-situ continuous test tracks the dynamic deformation of the thermosetting resin to evaluate the curing process.The results indicate that the phenolic resin is not sufficiently cured after heat treatment and curing under certain conditions.With the continuous test,the phenolic resin is further cured,the apparent glass transition temperature is moved to a higher temperature.The Tg of the first test of 130?-2 h phenolic resin was 127?,and the fourth test was 200?,which increased by 73?.And as the pre-curing temperature increases,the phenolic resin cures more fully.The storage modulus of RFRP at 130?-2 h changed particularly large,with a change of 21 MPa,while the curing conditions at 155 ? and 180 ?showed little difference,only 6.3 MPa and 3.1 MPa,respectively.At the test starting temperature of 28?,the RFRP of 130?-2 h,155?-2 h,180?-2 h has a storage modulus that is 31.94%,30.52% and 20.22% higher than that of phenolic resin.From the SEM image,it can be observed that the fiber is tightly bound to the resin,and there is residual resin on the surface of the fiber when the fiber is to be pulled out.At the same time,the effect of different heat treatment temperatures on the properties of ramie fiber and composite materials was studied.It is found that as the heat treatment temperature increases,the color of the ramie fiber gradually becomes darker,and the thermal expansion coefficient(CTE)of the composite material gradually decreases.Compared with untreated ramie fiber composites,the CTE of composites obtained by ramie fibers treated at 120?,150? and 180? decreased by11.02%,35.69% and 54.09%.And the thermal stability of ramie fiber and its composite materials have been improved.When using different heating rates to test the dynamic mechanical properties of the composite,it was found that the slower the heating rate,the higher the storage modulus of the composite,and the better the dynamic mechanical properties.