A novel nacre-inspired cfrp microstructure for improved strain to failure under in-plane compression

  • Garulli, Torquato (AMADE)
  • Katafiasz, Tomas (Imperial college London)
  • Greenhalgh, Emile (Imperial college London)
  • Pinho, Silvestre (Imperial college London)

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One notable weakness of Carbon Fibre Reinforced Polymers (CFRPs) is their performance under longitudinal compression. Typically, for unidirectional CFRPs, fibre-direction strength is much lower in compression than it is in tension, and the compressive failure process is sudden and catastrophic. This is due to it being triggered, for most CFRPs, by a material instability that leads to localised unstable fibre rotation and eventually to the formation of a kinkband [1]. Recently, design strategies inspired by biological materials have been used to devise CFRP microstructures with improved performances [2]; however, studies concerned with longitudinal compression loading [3] are lacking, despite it being a critical condition in many applications. In this study, we used an analytical approach to design a novel, nacre-inspired, tiled CFRP microstructure for improved strain to failure under longitudinal compression. Specifically, we engineered it to avoid failure by kinkband formation and to allow significant inelastic deformation of matrix regions among tiles. We manufactured prototype specimens with three different microstructure configurations and a baseline one, to be tested under 3-point-bending (3PB), having the novel microstructure on the side of the specimen undergoing compression. We performed in-situ 3PB tests in a scanning electron microscope (SEM) using a Deben micromechanical testing device, following damage evolution during the test. We then performed a detailed fractographic study to investigate the failure mechanisms of the novel microstructure and of the baseline specimen. The novel microstructure was able to prevent failure from being kinkband dominated; as a result, large inelastic matrix deformation and diffused damage were promoted. Furthermore, significantly larger strain to failure with respect to the baseline was obtained. The authors acknowledge the funding for this research provided by UK Engineering and Physical Sciences Research Council (EPSRC) programme Grant EP/T011653/1, Next Generation Fibre-Reinforced Composites: a Full Scale Redesign for Compression in collaboration with University of Bristol.