High performance quasi-isotropic thin-ply carbon/glass hybrid composites with pseudo-ductile behaviour in all fibre orientations

Mohamad Fotouhi,Meisam Jalalvand,Michael R Wisnom

doi:10.1016/j.compscitech.2017.08.024

Mohamad Fotouhi, Meisam Jalalvand + Show 1 more

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https://doi.org/10.1016/j.compscitech.2017.08.024

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Abstract

This study exploits the potential of thin-ply carbon/glass hybrid laminates to generate high performance Quasi-Isotropic (QI) composite plates that show pseudo-ductility in all fibre orientations under tensile loading, overcoming the inherent brittleness of conventional composites. Two types of QI lay-ups with 45° and 60° intervals, i.e. [45/90/-45/0] and [60/-60/0], were used to fabricate novel architectures of a QI T300-carbon laminate sandwiched between the two halves of a QI S-glass laminate. The fabricated plates were then loaded in all their fibre orientations. The laminates were designed by choosing an appropriate ratio of the carbon thickness to the laminate thickness using a robust analytical damage mode map. The experimental results verified the analytical predictions and showed a desirable pseudo-ductile failure in all the fibre orientations. Microscope images taken through the laminates thickness showed fragmentations (fibre fractures in the carbon layer) appearing only in the 0° carbon plies. A hybrid effect was observed, with an increase in strain and stress to failure of the carbon fibres, which was found to be dependent on the stiffness of the plies separating the 0° carbon plies and the plies adjacent to the 0° carbon plies. Altering the stacking sequence changes the stiffness of the separator and adjacent plies, therefore, leads to changes in the pseudo-ductile characteristics such as the initiation and final failure strains.

Highlights

Polymer-matrix composites use has been continuously increased in engineering applications due to their superior mechanical properties
Most composite structures are subjected to multiple loading orientations, the aim of this paper is to study the potential of thin-ply carbon/glass hybrid laminates and the orientation-dispersed method to generate high performance QI composite plates that show pseudo-ductility when loaded in all the fibres orientations under tension
The results show that the order of the plies and the distance between the 0 carbon and glass plies influenced the damage scenario, the free-edge delamination and the hybrid effect

Summary

Introduction

Polymer-matrix composites use has been continuously increased in engineering applications due to their superior mechanical properties. Two types of catastrophic failure modes occur in conventional hybrid composites; a) a single crack through the whole thickness of the laminate due to a high ratio of LSM to HSM thickness (improperly sized hybrid laminate), which results in a linear stress-strain curve (Fig. 1a, and b) a single fracture in the LSM instantaneously followed by unstable delamination, which appears on the stressestrain graphs as a significant load drop (Fig. 1b). This is a typical failure mode in conventional standard ply thickness hybrid laminates. Thin-ply UD and QI hybrids with different types of low strain and high strain fibres were introduced that generated the desired nonlinear stressestrain response and pseudo-ductility that avoids the catastrophic failure in laminated composites [17e19]

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