Evaluation of Fracture morphology of sintered fiber felt

The fracture morphology of stainless steel sintered fiber felt sample with 80% porosity sintered at 1000oC for 60 minutes is observed. It is found that most of the randomly distributed fibers at facture region are oriented to the tensile direction with obvious network structure loosing and necking. With high porosity and low sintering temperature, the development and growth of sintering joints in the 3D skeleton of sintered fiber felt become tough that results in low fiber to fiber bonding strength. The fiber felt are multilayer sintered 3D network material by stacking randomly laid stainless steel fibers. The sintering joints are easily damaged shear stress under tension that results into low tensile strength of sintered fiber felts. As a result, most of the randomly distributed fibers at frcture region move towards the tension direction without any obstacles owning to the sintering joints breaking.

Additionally the fracture process is slow due to the resistance coming from fibers rotation, randomly orientation fibers alignment and friction among fibers. So the sintering joints breaking by shearing off mechanism is an important failure mode for the sintered fiber felt in tension loading owning to high porosity, low sintering temperature, or short sintering time. The tensile strength of sintered fiber felt is low.

The fracture morphologies of sintered fiber felt with 75% porosity sintered at 1200oC for one hour. Necking phenomenon, network structure loosing and fibers alignment cannot be noticed.  Considering relatively low porosity, adequate sintering temperature and sintering time and the sintering joints among fibers can develop and grow successfully that result in strong interfiber joints. Fiber filament fracture occurs mainly to the joint rupture when tensile stress reaches its fracture strength.

As sintering joints are not damaged, the randomly distributed fibers cannot rotate towards the tension direction without any problems and the 3D network structure does not become loose. Tensilestrength of sintered fiber felt  is high and relatively low porosity, suitable sintering temperature and sintering time.