Indian Journal of Engineering & Materials Sciences Vol. 19, April 2012, pp. 135-143 FEM modeling of compressive deformation behaviour of aluminum cenosphere syntactic foam (ACSF) under constrained condition Raghvendra Khedle a *, D P Mondal b , S N Verma a & Sanjay Panthi b a Department of Mechanical Engineering, Rajiv Gandhi Prodyogiki Vishwavidyalaya, Air Port Road, Bhopal 462 003, India b Advanced Materials and Processes Research Institute (CSIR-AMPRI), Bhopal 462 026, India Received 18 April 2011; accepted 16 April 2012 The deformation behavior of aluminum cenosphere syntactic foam (ACSF) as a function of porosity, shell thickness, shell volume fraction and cenosphere volume fraction has been studied using finite element modeling of a representative unit cell of the respective material under both constrained and unconstrained conditions. The volume fraction of cenosphere and its shell thickness varies from 5% to 65% and 1 μm to 4 μm, respectively. It has been noted that as cenosphere volume fraction decreases, the plateau stress and Young’s modulus of these materials increases. While these values increase with increase in the shell thickness, i.e., shell volume fraction. The modulus and plateau stress increase considerably under constrained condition especially at low cenosphere volume fraction. The FEM predicted values are validated with experimental results and it is noted that the FEM predicted values are within the 12% variation of the experimental values. The proposed study thus shows that unit representative shell techniques are reasonably ideal and rapid method for predicting compressive deformation behavior of ACSF. Keywords: FEM, Aluminum cenosphere syntactic foam, Plateau stress, Micro-balloons Aluminum cenosphere syntactic foam (ACSF) are finding wide range of applications in aerospace and automobile due to their excellent combination of physical, tribological and mechanical properties 1-5 . The cenosphere is hollow and spherical in shape used as a space holder in aluminum metal for making aluminum syntactic foam 6-9 . The existence of these hollow particles along with stronger shell in the matrix results in a lower density, lower thermal coefficient, lower thermal conductivity and higher specific strength 8,9 . ACSF exhibits higher strength, excellent energy absorbing capability and isotropic mechanical properties due to extensive strain accumulation at relatively high stress 9 . These properties of ACSF are dependent on the size of micro-balloons and the preparation of the matrix material. There are two ways to change the properties of the respective material: first one is to change the volume fraction of cenosphere and second one is to use cenosphere of different wall thicknesses and sizes in the ACSF 11 . A few investigations have been carried out on the ACSF to study the effect of size, shape, volume fraction and distribution of cenosphere on its deformation behavior. ACSF with different porosity fraction could be made using different methods such as stir casting and melt in filtration 10 . Analytical and empirical attempts have been made to predict compressive strength of ACSF by various investigations 7-9,11 . The FE model predicated lower peak load, which is most likely due to the size effect exhibited by foam 12 . Wu et al. 7 predicted the compressive strength of ACSFs under quassi-static condition with the following equation: σ csf = C (σ m (1-f) 3/2 +σ wall [f (1-(1-t/r) 3 ) 3/2 ] … (1) Where, σ csf is the compressive strength of ACSFs, σ m is the yield strength of matrix, ƒ is the volume fraction of cenosphere, σ wall is the yield strength of cenosphere wall material, C is the empirical constant and t/r is the relative wall thickness of cenosphere (where t is wall thickness and r is radius of the cenosphere). They further reported that age hardened ACSFs exhibit higher plateau stress and high energy absorbing capacity as compare to the cast one. The above equation also states that the cenospheres with higher shell thickness provide higher plateau strength in ACSF. Similar kind of relation was also proposed by Balch and Dunand 8 . Mondal et al. 11 proposed a semi-empirical relationship of plateau stress of ACSF with cenosphere volume fraction and cenosphere shell strength and porosity fraction considering load partitioning between cenosphere and the matrix. According to Mondal et al. 11 the plateau ___________ *Corresponding author (E-mail: [email protected])
FEM modeling of compressive deformation behaviour of aluminum cenosphere syntactic foam (ACSF) under constrained condition
Jun 14, 2023
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