On Porosity Formation in Metal Matrix Composites Made with Dual-Scale Fiber Reinforcements Using Pressure Infiltration P
- PDF / 1,202,253 Bytes
- 15 Pages / 593.972 x 792 pts Page_size
- 62 Downloads / 193 Views
n process (PIP) for making metal matrix composites (MMCs), liquid metal is injected under pressure into a mold packed with reinforcing fibers. PIP is very similar to the resin transfer molding (RTM) process, which is used for the manufacture of near-net-shaped parts out of polymer matrix composites.[1] Both are characterized as liquid molding processes and consist of the following steps: (1) Dry fiber preforms made out of fabrics or fiber mats are placed in the mold. (2) Liquid matrix (monomeric thermosetting resin such as unsaturated polyesters or epoxies for PMCs, and molten metal or alloys for MMCs) is injected into the preform. (3) The liquid is allowed to harden through temperature control of the mold (exothermic thermosetting reaction for the resin and phase change for the metal). (4) The final netREIHANEH ETEMADI, Graduate Student, and KRISHNA M. PILLAI, Associate Professor, are with the Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211. Contact e-mail: [email protected] PRADEEP K. ROHATGI, Professor, is with the Department of Material Science and Engineering, University of Wisconsin-Milwaukee. SAJAD AHMAD HAMIDI, Research Associate, is with the Department of Civil and Environmental Engineering, University of Wisconsin-Milwaukee. Manuscript submitted May 18, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
shaped composite part is removed from the mold. An important advantage of the liquid infiltration processes is the production of near-net shape composite parts from preforms designed using different reinforcements for optimal mechanical and other properties.[2,3] The use of the woven or stitched fabrics as reinforcements is increasing as they provide a convenient way of improving the mechanical properties by ensuring higher fiber volume fractions through clustering of fibers as fiber tows or bundles. Porosity* is a major defect found in *In this study, the term ‘‘void volume fraction’’ is used to quantify the void space inside a preform as a fraction of the total preform volume, while the presence of voids inside the composite will be referred to as the ‘‘porosity.’’
these fabricated composites which adversely affects their fatigue properties. Of the two types of PIPs, we will be studying the gas PIP (gas pressure infiltration process) where a pressurized gas is used to push the liquid metal into the dry preform. The processing conditions have a major influence on the porosity content of MMC composites synthesized by the gas PIP. Another major source for porosity formation during this process is solidification shrinkage, which happens during the metal phase
change. In the present study, the effect of changes in the processing parameters of infiltration temperature and pressure on the porosity content of MMC samples synthesized by gas PIP is studied. In addition, the effect of matrix shrinkage on the porosity content of MMC samples is explored using a zero-shrinkage alloy as the matrix. The phenomenon of porosity formation during the making of MMC using PIP from 3D-woven reinforc
Data Loading...
