Characterization of the shear/compression failure envelope of Rohacell foam

• Published in: Polymer testing 2004-02, Vol.23 (1), p.51-57
• Main Authors: Benderly, D., Putter, S.
• Format: Article
• Language: English
• Subjects: Analytical model; Applied sciences; Cellular; Core material; Exact sciences and technology; Failure envelope; Flexural testing; Foam; Forms of application and semi-finished materials; Polymer industry, paints, wood; Rohacell; Sandwich structure; Technology of polymers
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/S0142-9418(03)00061-8

Four-point flexural testing of sandwich structures is often used for the determination of the shear strength of the core material. The accuracy of this test was evaluated using finite-element modeling. The model results show that the measured average shear stress may be inaccurate due to shear stress variations within the sample and the presence of supermiposed compressive stresses. A modified experimental test method was developed to ensure a more homogeneous shear stress field. Using this test method, controlled combinations of shear and compressive stress can be generated within the polymeric foam, allowing evaluation of the shear/compression failure envelope. Results for a Rohacell polymeric foam show that, at the temperatures evaluated, the compression/shear failure envelope is elliptical. On a normalized plot of the failure envelope, the data for all temperatures coincide on a circular plot. Use of this failure envelope approach can reduce the amount of testing required to acquire design data.