Effect of tensile strength of fiber felt with different porosities
Porosity as an essential factor of the fiber felt has a extensive influence on the tensile strength. The felt samples were sintered at 1200oC for 1 hour. The samples undergo a linear elastic range after receiving a short-term initial nonlinear elastic deformation and then undergo plastic deformation and hardening limit. The tensile strength of stainless steel fiber felt samples with 75%, 80%, and 85% porosity reaches 44.5 MPa, 30.5 MPa and 19 MPa respectively. The yield strength of fiver felt samples with 75%, 80% and 85% porosity attains 25 MPa, 17.5 MPa and 10.5 MPa respectively. It can be observed that the tensile strength and yield stress of the fiber felt are excellent. The reason can be that laminar and jagged surface structures increase the friction between fibers and offer occlusal force to hook fibers that favour strong sintering joints formation.
Effect of sintering on tensile property of fiber felt
Considering essential manufacturing parameters, sintering temperature and sintering time have a major effect on the forming process of the fiber felt.
The tensile strengths of samples sintered at 1000oC, 1100oC and 1200oC are 16 MPa, 28.2 MPa and 30.5 MPa respectively. With increase in sintering temperature, material movement becomes active hence enhancing the development of sintering joints that make bonding of interfiber stronger. Additionally, the yield stress of samples sintered at 1000oC is 13.3 MPa and yield stress of samples sintered at 1100oC and 1200oC are almost identical and up to 17.5 MPa. Hence, it can be understood that the sintering temperature limit should be between 1100oC to 1200oC to receive high strength.
Sintering temperature of sintered fiber felt has considerable effect on its surface morphology. The melting phenonmenon occurs when sintering temperature is 1300oC. At this point, the laminar and jagged structures are lost and the surface morphology of stainless steel fiber felt become smooth. So the sintering temperature should not be more than 1200oC to prepare the sintered fiber felt with hard surface morphology.
The tensile strength increases from 33 MPa to 49.5 MPa with sintering time varying from 30 minutes to 120 minutes. Although, the tensile strength reduces to 42.8 MPa when widely increasing the sintering time to 240 minutes. It can be observed that increasing the sintering time suitably can enhance the development and growth of sintering joins because of material of contact regions among fibers has sufficient time to diffuse and tensile strength is enhanced. Although, wide sintering time makes grains coarsening that leads to tensile strength reduction and elongation enhancement. Additionally, the yield stress of samples sintered for 60 minutes and 120 minutes are almost same and up to 25 MPa. So, the suitable sintering time should be about 60 minutes to 120 minutes.
It is found that surface morphology of sintered fiber felt are slick and the laminar and jagged structures lost. So, the sintering time should not be longer than 120 minutes to maintain the rough surface of Sintered fiber felt.