Evaluation of the tensile strength of compacts using square samples produced through triaxial decompression

Jovana Radojevic1, Edward Yost2, Ariel Muliadi2, Chen Mao2, Antonios Zavaliangos1

1 Drexel University, Philadelphia, PA
2 Genentech, South San Francisco, CA

When N. Hiestand proposed that pharmaceutical materials and formulations should be characterized using a set of indices (commonly known as the Hiestand indices [1]), he recommended that their tensile strength should be assessed by lateral compression of two square samples (one with a central  hole and one without), produced through compaction followed by a triaxial decompression process. In his earlier work [2, 3], E.N. Hiestand had proposed that many compacts produced by triaxial decompression are in general stronger than those created in a regular “rigid” die and thus samples produced by triaxial decompression could allow for the determination of the “true” strength of a material. 

Recently, Huxley Bertram Inc. introduced a triaxial decompression option for their compaction simulator. In an effort to provide an evaluation of this setup, and in view of our modern and more complete understanding of the mechanics of these tests, this study focused on:

  1. a finite element analysis of the lateral compression of square specimens 
  2. an assessment of the operation of the HB device and
  3. an experimental evaluation of the strengths of representative materials with this setup.

References:
1.         Hiestand, H.E.N. and D.P. Smith, Indices of tableting performance. Powder Technology, 1984. 38(2): p. 145-159.
2.         Hiestand, E.N., et al., Physical processes of tableting. Journal of Pharmaceutical Sciences, 1977. 66(4): p. 510-519.
3.         Hiestand, E.N. in Int. Conf. on Powder Tech. and Pharm. 1978. Basel, Switzerland

Jovana Radojevic, Ph.D.

Jovana Radojevic recently received a PhD in Materials Science and Engineering from Drexel University in Philadelphia, PA. She holds a Master’s degree in Materials Engineering from University of Belgrade and a Bachelor’s degree in Mechanical Engineering from Temple University. Her doctoral thesis work focused on residual stresses that affect post-compaction evolution of strength in cold compacted powder composites. Her research interests include experimental and modeling work of powder compaction as well as investigation of methods that alter microstructure of powders and lead to an improved performance of compacted powder mixtures. She is an active member of American Association of Pharmaceutical Scientists (AAPS) and Materials Research Society (MRS).

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