Preparation Of Nanometer Al₂O₃/PTFE Composite And Study On Mechanical Property

In this paper, PTFE and Al2O3/PTFE composite were prepared using the process ofcold pressure and sintering. The process parameters were determined by compression testand sintering test.A series of ratcheting experiments under uniaxial loading were conducted onpure PTFE. The effects of loading rate, mean stress and stress amplitude onratcheting strain were studied. It is shown that ratcheting strain increase with theloading rate decreased, but when loading rate is higher than 40N/S, there is littleeffect on ratcheting strain rate. The ratcheting strain and ratcheting strain rateincrease with mean stress and stress amplitude increased, and mean stress has moreeffects on them. Ratcheting strain rate decayed quickly with the increase of thenumbers of cycle. The U-P-R model was used to predict the ratcheting behavior ofpure PTFE. The results of experiment and prediction coincided well in some cases,but not for all cases.A series of compression experiments and ratcheting experiments wereperformed on different mass fraction nanometer Al2O3/PTFE composite. It is shownthat as a whole, compression modulus has the upwards with the increase ofnanoparticles Al2O3' fraction in PTFE. Compression strength increase with Al2O3fraction in PTFE until the maximum at the value of 10% fraction, then go down. TheSEM analysis for fracture surface of specimen has shown that the failure ofcomposite transformed from ductile material to brittle material with the increase ofAl2O3' fraction. PTFE filled with Al2O3 decrease the value of ratcheting strain ofAl2O3/PTFE composite markedly. Between 5% and 15% there is an optimum valuewhich makes the ratcheting strain being the minimum.