Fabricating of Multiscale Composite Materials Based on TPU reinforced by carbon fibre and Graphene Nanoplatelets (GNPs)

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Abstract

This project focuses on manufacturing novel carbon fibre (CF) multiscale composites (MSCs) based on nanocomposite matrices of thermoplastic polyurethane (TPU) and graphene nanoplatelets (GNPs). The main aim of this study is to obtain innovative MSCs with optimised electrical, thermal and mechanical properties that make them applicable to aerospace, transportation and electrical devices. The TPU with 70 wt. % hard segments (HS) was filled with three different sizes of GNPs, with average particle diameters of 5 microns (GNPM5), 15 microns (GNPM15) and 25 ­microns (GNPM25), and reinforced with CF fabric to produce MSCs. The effect of GNP size and annealing treatment on the thermal dynamic, mechanical and electrical properties of TPU-70 HS and TPU70/CF laminate were investigated. Following these tests, the best MSCs that could be obtained were used to study the effect of GNP content on the Mode-I interlaminar fracture toughness (ILFT), impact-damage resistance and damage tolerance of TPU70/CF laminates. It was found that the tensile modulus (E) and flexural modulus (FM) of polymers-NCs matrices were affected by both the size of GNPs and annealing treatments. While the addition of GNPM25 yielded an impressive improvement in the E and FM of TPU-70 HS, the annealing treatment caused a slight reduction owing to the disruption of phase separation and restacking of the GNP flakes. However, the neat TPU-70 HS exhibited significant improvements in the E and FM after annealing due to the formation of microcrystalline hard domain (HD) phase separation, which caused an increase in stiffness. The in-plane and out-of-plane electrical conductivity and the thermal conductivity of NCs combined with GNPM15 and GNPM25 showed a significant improvement compared to that of neat TPU-70 HS. The same results of E and FM were reported for MSCs based on GNPM25, where the E and FM enhanced by 19% and 105% compared with that of TPU70/CF laminates and reduced by 11% and 4% respectively after annealing. The out-of-plane electrical conductivity of TPU70/CF composites showed a noticeable improvement upon incorporating GNPM15 and GNPM25. Conversely, the thermal conductivity of the TPU70/CF laminate exhibited a significant improvement upon the addition of GNPM5 compared to that of GNPM15 and GNPM25. This result might be attributed to the non-uniform dispersion of GNPM5 due to its small size, leading to an increase in local thermal diffusivity. Since the best tensile, flexural and electrical properties were ascribed to the NCs and MSCs combined with GNPM25, these materials were selected and different weight percentages of GNPs (0.5, 2.5 and 5) were used. The MSCs combined with 0.5 wt.% GNPs showed a slight improvement in the GIC-Max and GIC-Prop compared with that of the TPU-70 CF, while a high loading caused a significant reduction in both GIC initiation and propagation. In addition, both the impact-damage resistance and residual compressive strength of MSCs at high GNP loading and impact energy levels experienced a significant reduction compared to TPU70/CF laminate. To conclude, adding GNPM25 to the TPU70/CF laminate produced MSCs with enhanced in-plane and out-of-plane electrical conductivity and thermal conductivity. However, some mechanical properties were sacrificed, such as ILFT, impact-damage resistance and residual compressive strength. This was especially true at high loading, which was used to reach the percolation threshold for GNPs with high aspect ratio.

Keyword(s)

Multiscale composites; graphene nanoplatelets nanocomposites

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