A numerical investigation into the electrical properties of through-thickness reinforced composites
Topic(s) : Manufacturing
Co-authors :
Bing ZHANG (UNITED KINGDOM), Mudan CHEN (UNITED KINGDOM), Jingyi ZHANG (CHINA), Giuliano ALLEGRI (UNITED KINGDOM), Stephen HALLETT (UNITED KINGDOM)Abstract :
1. Introduction
Fibre-reinforced polymer (FRP) composites are most used in the form of lamination, where plies are stacked up, and the fibre orientation in each ply is tailored to maximise the structural properties in the required in-plane direction. However, their out-of-plane properties are lower than in-plane. Thus, through-thickness reinforcement (TTR), typically via Z-pinning, Tufting and Stitching, is introduced to composites to improve their out-of-plane properties. TTR elements can be in principle made of any materials that can be processed into small diameter rods or threads, thus the last decade has seen an increasing study on the non-structural function of TTR [1]. A potential application of TTR is to tailor the electrical conductivity of composites [1,2]. Experimental studies in this area are sparse and costly. Thus, it is beneficial to develop a numerical model to comprehensively investigate the effects of TTR on the electrical properties of composites.
2. Present work
A critical review on the state of art of multifunctional TTR will be firstly presented, covering electrical and thermal properties, sensing, actuation and self-healing.
This work then employs a high-fidelity ply-by-ply model to examine the influence of TTR on the electrical properties of composites, considering typical microstructures of composites with TTR, such as fibre waviness, resin pocket, fibre crimp due to TTR insertion, and TTR misalignment. In particular, when TTR areal density is high and pin misalignment is severe, the microstructure of composites with TTR become quite complicated. An automated meshing tool is developed to describe these features, and their effects on local electrical conductivity are described by a mathematical formula that is based on the fibre volume fraction. The modelling strategy is verified against experiment results of an IMA/M21 quasi-isotropic composite laminate with composite and metallic Z-pins as TTR, as published in Ref. [2]. Figure 1 shows the electric potential predicted in the laminate when electrical current is rejected from the top left corner of top surface and exits from the centre of bottom surface.
Figure 2 shows that the numerical results agree well with experiments for both in-plane and out-plane measurements. TTR can significantly change the conductivity of composites, but depending on where current is injected to and exits from the laminate. The current injection pattern, along with other factors such as TTR areal density and TTR misalignment will be thoroughly discussed and analysed, drawing insights and conclusions from an extensive dataset generated by the numerical modelling strategy.
Fibre-reinforced polymer (FRP) composites are most used in the form of lamination, where plies are stacked up, and the fibre orientation in each ply is tailored to maximise the structural properties in the required in-plane direction. However, their out-of-plane properties are lower than in-plane. Thus, through-thickness reinforcement (TTR), typically via Z-pinning, Tufting and Stitching, is introduced to composites to improve their out-of-plane properties. TTR elements can be in principle made of any materials that can be processed into small diameter rods or threads, thus the last decade has seen an increasing study on the non-structural function of TTR [1]. A potential application of TTR is to tailor the electrical conductivity of composites [1,2]. Experimental studies in this area are sparse and costly. Thus, it is beneficial to develop a numerical model to comprehensively investigate the effects of TTR on the electrical properties of composites.
2. Present work
A critical review on the state of art of multifunctional TTR will be firstly presented, covering electrical and thermal properties, sensing, actuation and self-healing.
This work then employs a high-fidelity ply-by-ply model to examine the influence of TTR on the electrical properties of composites, considering typical microstructures of composites with TTR, such as fibre waviness, resin pocket, fibre crimp due to TTR insertion, and TTR misalignment. In particular, when TTR areal density is high and pin misalignment is severe, the microstructure of composites with TTR become quite complicated. An automated meshing tool is developed to describe these features, and their effects on local electrical conductivity are described by a mathematical formula that is based on the fibre volume fraction. The modelling strategy is verified against experiment results of an IMA/M21 quasi-isotropic composite laminate with composite and metallic Z-pins as TTR, as published in Ref. [2]. Figure 1 shows the electric potential predicted in the laminate when electrical current is rejected from the top left corner of top surface and exits from the centre of bottom surface.
Figure 2 shows that the numerical results agree well with experiments for both in-plane and out-plane measurements. TTR can significantly change the conductivity of composites, but depending on where current is injected to and exits from the laminate. The current injection pattern, along with other factors such as TTR areal density and TTR misalignment will be thoroughly discussed and analysed, drawing insights and conclusions from an extensive dataset generated by the numerical modelling strategy.