Tailoring of Thermo-Mechanical Properties of Hybrid Composite-Metal Bonded Joints

Abstract

Metallic substrates and polymer adhesive in composite-metal joints have a relatively large coefficient of thermal expansion (CTE) mismatch, which is a barrier in the growing market of electric vehicles and their battery structures. It is reported that adding carbon nanotubes (CNTs) to the adhesive reduces the CTE of the CNT enhanced polymer adhesive multi-material system, therefore when used in adhesively bonded joints it would, theoretically, result in low CTE mismatch in the joint system. The current article presents the influence of two specific mass ratios of CNTs on the CTE of the enhanced polymer. It was observed that the addition of 1.0 wt% and 2.68 wt% of multi-walled CNTs (MWCNTs) decreased the CTE of the polymer adhesive from 7.5e-5 1/C (pristine level) to 5.87e-5 1/C and 4.43e-5 1/C, respectively by 22% and 41% reduction. The reduction in the CTE was predicted, theoretically, which showed that CTE should have been reduced to 3.6e-5 1/C (52% reduction) and 1.4e-5 1/C (81% reduction). This may be due to the fact that, Raman spectroscopy of the MWCNTs identified defects in the raw material, and scanning electron microscopy (SEM) identified agglomeration of MWCNTs on the surface and cross-section of the modified polymers.

Development and testing of carbonaceous tin-based solder composites achieving unprecedented joint performance

“…• grain improvement strengthening Slight increase was observed in the transition from the as-received C-Solder® to 0.01 wt% CB, and a significant increase in 0.05wt% CB enhanced C-Solder® (Figure 10) by nearly 0.85 HV. The increase was also seen in the case of SWCNT addition at 0.01wt% and 0.05wt% however lower at 0.05% wt.% SWCNT, attributed to the extensive agglomeration shown in Figure 6(g), compared to that of the 0.01wt% sample observed to attain a more uniform SWCNT dispersion in Figure 6 (HV≈ 14-15), C-Solder® in Figure 10 showed a higher hardness value [21,25], mainly due to the presence of chromium in the solder matrix which restricts dislocation motions [39]. This restriction can be overcome by addition of carbon nanomaterials according to our phenomenological study above, i.e.…”

“…The failure load in almost all joints soldered by 0.01 wt.% reinforced solders was lower than the pristine solder. This can be attributed to the fact that in some areas in the solder matrix, the carbon nanomaterials coming into contact with each other, form clusters due to strong Van der Waals forces between them [27,25]. This may hinder the bonding between the nanomaterials and the solder matrix which in turn results in cluster induced porosity that act as potential stress concentration site and promote joint failure.…”

“…The study includes a comprehensive analysis of data from microstructural characterisation, thermal analysis and mechanical shear performance of soldered joints utilising the pristine solder, and carbon nanomaterials reinforced solder with 0.01 and 0.05 wt.% loading contents. The joint strength was evaluated using standard single-lap soldered joints made of aerospace grade aluminium substrates, and under quasi-static loading conditions [12,25].…”