Predicting the indentation load of FRP facesheet / foam core sandwiches

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Çetin A., Uzay Ç., Tütüncü N., Geren N.

Structures, vol.62, 2024 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 62
  • Publication Date: 2024
  • Doi Number: 10.1016/j.istruc.2024.106266
  • Journal Name: Structures
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: Fiber-reinforced polymer (FRP) composite facesheet, Flexural stiffness, Indentation failure, Modified analytical model, Sandwich beam, Three-point bending test
  • Çukurova University Affiliated: Yes


Due to concentrated bending loads, indentation is a common failure mode for sandwich structures. Indentation restricts the efficient use of sandwiches and is seriously affected by the sandwich design. Currently-used Traditional Analytical Models (TAM) are insufficient to predict the indentation load of the sandwiches with fiber-reinforced polymer (FRP) composite facesheets and foam core. Because of anisotropic features of FRP composites, experimental stiffness data is required to implement TAM. Their prediction accuracy is also disputable for different fiber orientations of facesheets. In this study, a modified analytical model (MAM) was developed to predict core yield and indentation failure loads without needing the experimental data of FRP composite facesheets. The modification is applied to currently-used two different traditional indentation models, and it is based on the analytically-obtained stiffness terms. The results obtained by MAM were then compared with the results determined by TAM and with the flexural test results of various sandwich structures. The modified analytical model, presented herein, yielded more accurate results than the TAM even for angle-ply configurations. An analytical solution to predict indentation is ultimately more attractive to structural sandwich designers because it provides rapid predictions that eliminate trial-and-error experimental efforts.