Sputter Deposited Metal Layers Embedded in Composites—From Fundamentals to Applications

Abstract

Due to the low heat flux towards the substrate, magnetron sputter deposition offers the possibility to deposit thin films on heat sensitive materials such as fiber-reinforced polymers, also known as composite materials. Passive thermal probe measurements during the sputter deposition of metal layers show indeed that the temperature increase remains well below 25 °C for film thicknesses up to 600 nm. The latter thickness threshold is based on the influence of embedded metal films on the adhesion of the composite plies. Films thicker than this threshold deteriorate the mechanical integrity of the composite. The introduction of the uncured composite in the vacuum chamber strongly affects the base pressure by outgassing of impurities from the composite. The impurities affect the film properties as illustrated by their impact on the Seebeck coefficient of sputter deposited thermocouples. The restrictions to embed thin films in composites, as illustrated by both the heat flux measurements, and the study on the influence of impurities, are however not insurmountable. The possibility to use embedded thin films will be briefly demonstrated in different applications such as digital volume image correlation, thermocouples, and de-icing.

Embedded Sensors for Structural Health Monitoring: Methodologies and Applications Review

“…Regarding applications obtained in composite materials, a set of embedded SHM techniques has been developed to incorporate the structural components [ 107 , 108 , 109 , 110 , 111 , 112 , 113 ]. Starting with SHM techniques that have capacitive methods as their basis, the scientific community has developed technologies that allow for the monitoring of the deformations that a particular component is subjected due to dynamic impacts by including a pair of wires in adjacent layers to obtain a complex condenser.…”

Embedded Sensors for Structural Health Monitoring: Methodologies and Applications Review

“…For applications obtained in composite materials, a set of SHM embedded techniques has been developed to incorporate the structural components [110][111][112][113][114][115][116]. Starting with SHM techniques that have Capacitive Methods in their base, the scientific community has developed technologies that allow the deformations monitoring that a particular component is subjected due to dynamic impacts, by including a pair of wires in adjacent layers to obtain a complex condenser.…”

“…The methodologies for integrating this type of sensors or materials are fundamentally based on a reinforced concrete structure, in the inclusion of sensors during the production phase and in polymer matrix composites, in the inclusion of these before the curing process. However, news approach to methodologies for obtaining smart sensors materials are beginning to emerge, such as the use of magnetron sputter deposition to deposit thin films on heat sensitive materials such as fibre-reinforced polymers, also known as composite materials [115].…”

“…Embedded sensors allow the addition of value or functionalities in structural components; however, they can compromise the structural properties of the host material. Therefore, the work developed by Cougnom et al [115] presents an alternative that does not deteriorate the properties but rather guarantees an increase depending on the typology of the thin films deposited. Consequently, this composite material allows the fabrication of single-metal thermocouple thin and heating elements.…”

Metallisation of Textiles and Protection of Conductive Layers: An Overview of Application Techniques

“…Among the above-mentioned variations, the magnetron sputtering is the most frequently employed process for the deposition of thin, durable layer of metals (Cu, Ti, Ag, Al, W, Ni, Sn, Pt), metal oxides (TiO 2 , Fe 2 O 3 , WO 3 , ZnO) or non-metallic compounds (Si, graphite, ceramic) on various types and forms of flat textiles [108], providing a sophisticated film thickness and user-defined patterns on a substrate [109] for diverse applications, i.e., electroconductive transmission lines for emergency and security services [110], flexible strain sensors for real-time monitoring of human motions [111], EMI shielding protective gear [112,113], etc. Moreover, the transfer from laboratory results to industrial applications is rather straightforward, since magnetron sources can be upscaled easily [114]. The basic mechanism of the magnetron sputtering process is presented in Figure 6a.…”