| Strain gage based load cell are widely used in the measurement of many kindsof high-precision instrument, however, the designation、 manufacture ofhigh-precision load cell in our country are relatively backward. The critical pointthat restrict its improvement is the manufacturing technique of the substrate in loadcell. To satisfy the operating requirement of high-precision sensors, a kind of filmsubstrate made of glass fiber(GF) reinforced epoxy resin composites was developed,and the morphology, microstructure and mechnical properties of the substrate werestudied by kinds of experimental analysis. The main contents and results are asfollows:Firstly, the solid and liquid epoxy resin were mixed with each other in theinternal mixer, then the film substrate based epoxy resin was obtained, to examineits properties with the traditional substrate made with solvent, dynamic mechanicalanalysis(DMA) was used to have a test. The result showed that under glasstransition temperature(Tg), the storage modulus of solvent-free film substrate wastwo times of that of solvent film substrate, and the creep of solvent-free substratedecreased fast with increasing temperature compared with the solvent substrate.Secondly, different contents of glass fiber with the diameter of1m weremixed with epoxy resin in the internal mixer, and then the substrate made of glassfiber reinforced epoxy resin was obtained. The distribution of glass fiber withdifferent contents in the epoxy resin were observed with Scanning ElectronMicroscopy(SEM), and it turned out that only those with10%glass fiber or morecan interweave with each other homogeneously. Different curing pressure of epoxyresin film were observed with optical microscope, the result showed that the surfaceof film cured under high pressure was smooth, then pressurized curing was adopted.Thirdly, the curing process of pure epoxy resin and glass fiber reinforcedepoxy composites were investigated with Differential Scanning Calorimetry(DSC).From the curing curve of pure epoxy resin, every step curing temperature can beobtained: gelation temperature was100℃, curing temperature was130℃, postcuing temperature was160℃, then Tg of epoxy resin with different curing agentcontents were tested, the result showed that epoxy resin with10%curing agentcontens has the highest Tg. The curing process of glass fiber reinforced epoxycomposites were investigated in the same way, the result showed that glass fiberaffected the curing process of epoxy resin, and the epoxy resin with glass fiber canbe cured completely when the post curing temperature increased to180℃. Tg ofepoxy resin with different glass fiber contents were tested with DMA and DSC, similar Tg were obtained from these two methods.Finally, the dynamic mechnical properties, creep and thermostability of epoxyfilm substrate with different glass fiber contents were tested with DMA andThermogravimetry(TG), the creep and recovery of each substrate were comparedunder different temperatures and stresses. The result showed that under lowtemperature, creep of each substrate was quite small, with temperature increasing,the creep resistance of20%GF reinforced epoxy has an obvious improvementcompared with that of pure epoxy and10%GF reinforced epoxy. Therefore,20%GFreinforced epoxy resin substrate can improve the precision of measurement andoperating temperature. The TG result showed that the onset decompositiontemperature of20%GF reinforced epoxy resin increased to320℃compared withthat of281℃of pure epoxy resin. |
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