Failure mechanisms of biological crossed-lamellar microstructures applied to synthetic high-performance fibre-reinforced composites

Abstract

This paper investigates whether the toughening mechanisms of a biological crossedlamellar microstructure can be reproduced in a synthetic high-performance carbon fibre/epoxy matrix composite. The mechanics of the failure process in synthetic crossedlamellar microstructures was investigated using the Finite Element Method. This enabled the design of a high-performance carbon-fibre reinforced polymer (CFRP) with such microstructure. Two different procedures were then developed to synthesise the first crossed-lamellar microstructures in CFRP in the literature. Test specimens were subsequently manufactured. Three-point bend tests were carried out in an SEM environment, showcasing the damage diffusion capability of the microstructure under stable conditions. The results show that the crossed-lamellar microstructure can be synthesised in CFRP with good accuracy, and that the mechanical toughening mechanisms associated with the natural crossed-lamellar microstructures can be reproduced in this synthetic material.

A three-level hybrid metal/in-plane-CFRP/crossed-lamellar microstructure concept for containment applications

“…shown to be potentially excellent [9], crossed-lamellar microstructures have no fibres in the direction of loading, which limits their use in practical engineering applications. Therefore, in this work, for the first time in the literature, we propose a hybrid metal/CFRP composite with in-plane fibres and a bio-inspired crossed-lamellar layer, and demonstrate that this novel microstructure preserves its structural integrity during failure while the in-plane fibres provide it stiffness and strength.…”

“…Additionally, in the middle layer, only half the thickness of the +45 • and −45 • 90 plies was included in the model due to its periodicity. An interface with thickness t I (Table 2) was also modelled between the ±45 • plies to allow for debonding and subsequent frictional sliding of the plies using an elasto-plastic constitutive law with linear softening [9]. The CFRP in the middle layer was modelled as having non-linear shear behaviour in the local 12-direction following the Ramberg-Osgood relationship and was subsequently allowed to fail in shear using anisotropic plasticity with linear softening.…”

“…x-axis using periodic boundary conditions on the left and right faces ( Figure 3). While these boundary conditions are relatively trivial for the x and y displacement components [9], a new term was derived for the z displacement component to account for the zigzagshaped boundaries.…”

“…Upon bending, the shell dissipates energy through parallel tunnel cracking in the inner layer, crack deflection as the cracks reach the middle layer, and crack bridging, debonding and frictional sliding as the cracks grow in the middle layer [10]. Research into the [8], copyright 2004 American Chemical Society) has (b) a crossed-lamellar microstructure (not to scale) [9].…”

“…Previous research into CFRPs with crossed-lamellar microstructures [9,11] has shown that the damage mechanisms of the natural composite can be reproduced in CFRP, and that the damage diffusion can be further enhanced with a microstructure that has inner and outer layers made of a ductile material.…”