Experimental and numerical investigation of intra-laminar energy dissipation and size effect in two-dimensional textile composites

Marco Salviato, Kedar Kirane, Shiva Esna Ashari, Zdeněk P. Bažant, Gianluca Cusatis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Design of large composite structures requires understanding the scaling of their mechanical properties, an aspect often overlooked in the literature on composites. This contribution analyzes, experimentally and numerically, the intra-laminar size effect of textile composite structures. Test results of geometrically similar Single Edge Notched specimens made of [0]8 epoxy/carbon twill 2 × 2 laminates are reported. Results show that the nominal strength decreases with increasing specimen size and that the experimental data can be fitted well by Bažant's size effect law, allowing an accurate identification of the intra-laminar fracture energy of the material, Gf. The importance of an accurate estimation of Gf in situations where intra-laminar fracturing is the main energy dissipation mechanism is clarified by studying numerically its effect on crashworthiness of composite tubes. Simulations demonstrate that, for the analyzed geometry, a decrease of the fracture energy to 50% of the measured value corresponds to an almost 42% decrease in plateau crushing load. Further, assuming a vertical stress drop after the peak, a typical assumption of strength-based constitutive laws implemented in most commercial Finite Element codes, results in an strength underestimation of the order of 70%. The main conclusion of this study is that measuring accurately fracture energy and modeling correctly the fracturing behavior of textile composites, including their quasi-brittleness, is key. This can be accomplished neither by strength- or strain-based approaches, which neglect size effect, nor by LEFM which does not account for the finiteness of the Fracture Process Zone.

Original languageEnglish (US)
Pages (from-to)67-75
Number of pages9
JournalComposites Science and Technology
Volume135
DOIs
StatePublished - Oct 27 2016

Keywords

  • Damage mechanics
  • Microplane model
  • Non-linear fracture mechanics
  • Size effect
  • Textile composites
  • Two-dimensional composites

ASJC Scopus subject areas

  • Ceramics and Composites
  • Engineering(all)

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