The world of smart healable materials

Bonded repair of composite aircraft structures: A review of scientific challenges and opportunities

In most areas where weight reduction is crucial, carbon fiber reinforced composites (CFRPs) are an excellent choice. Carbon fiber, besides its structural role, can be applied for several secondary functions as well, based on its electrical properties; for example, it can be used for crosslinking, welding, as a sensor and it can also facilitate self-healing. By merging these functions, a multifunctional part or structure can be created. In this article, we review multifunctional application examples of reinforcing carbon fiber. The focus is on utilization: which additional function and what physical layout can be used with CFRP. In a summarizing table (Table 1), we classified the presented examples according to their secondary function, the material used and the physical layout. With the combination of different functions, important materials can be created for the energy and transportation industry, for autonomous vehicles and for Industry 4.0.

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Multifunctional application of carbon fiber reinforced polymer composites: Electrical properties of the reinforcing carbon fibers – A short review

This paper presents a comprehensive overview of the process of induction welding of thermoplastic composites. The main objective is to provide a deeper insight into the nature of the induction welding process and to summarise the investigative effort that was put into it by a large group of researchers. The main focus is put on the types of heat generation mechanisms during the induction heating process and the parameters that govern the welding process (frequency, power, pressure, residence time), as well as on the secondary phenomena that can influence the quality of the weld. An overview of the experimental procedure is also presented, with an emphasis on the experimental set-up. Finally, a brief overview of the modelling of the heat generation mechanisms and the induction welding process is presented.

Induction welding of thermoplastic composites—an overview

Since the late 1980s a small number of research groups have been attracted with the idea of using induction heating technology for the processing of fibre reinforced polymer composites. Induction technology is suitable for the processing of thermoplastic and thermoset polymer materials but requires special susceptor additives (conductive materials) either in the form of structured fibres and fabric or particulate that can transform the electromagnetic energy into heat. This paper aims to summarize the principles of induction heating with respect to polymer composites processing taking a look first at material and equipment based process influences. State of the art applications and research activities are then reviewed, from thermoplastic composite welding, thermoset curing, selective material heating and fast mould heating technologies. Current simulation possibilities and available software tools have also been covered. Finally, some new ideas and possibilities for future developments in the field of polymer composites processing have been discussed.

The heating of polymer composites by electromagnetic induction – A review

A unified approach, considering three possible heating mechanisms: fiber (Joule losses) and fiber crossover junction (dielectric hysteresis and contact resistance), to identify dominant heating mechanisms during induction processing of conductive fiber reinforced composites is presented. Non-dimensional parameters were proposed to identify the relationships between heating mechanisms and process and material parameters. Parametric studies showed that junction heating mechanisms dominate fiber heating for the material systems considered, with the exception of relatively low contact resistance (< 10 3). Results for dielectric hysteresis and low contact resistance were consistent with individual models in the literature. A design map relating the three mechanisms is presented that can help identify the dominant heating mechanism, given the properties of the composite.

A Study on the Induction Heating of Conductive Fiber Reinforced Composites

The advantages of using adhesives for joining composite structures are now well accepted. Adhesive joints may offer, over bolted joints, advantages such as a lower assembly weight, a superior stress transfer and an improved fatigue resistance. However, in some applications the above advantages may be offset by the processingconditions required to cure the adhesive. Indeed, in the conventional oven curing process the thermal energy must diffuse through the composite layers to heat the joint interfaces, resultingin longand expensive processingtime as well as wasted energy. A novel method of achieving adhesive bonds is addressed in the present study. The method of electromagnetic heating is well suited for rapid and efficient localized heatingof adhesive bond lines, provided suitable susceptors are used at the interfaces. This paper presents the results of a study on the use of induction heating for bondingcomposite adherends. Single-lap shear tests and double-cantilever beam fracture experiments were perfor...

A comparison of oven-cured and induction-cured adhesively bonded composite joints

A numerical model is proposed to describe in-plane heat generation spatial response during induction processing of carbon fiber-reinforced thermoplastics. The model is based on a unified approach that considers three possible heating mechanisms: fiber heating (Joule losses in fiber), noncontact junction heating (dielectric hysteresis), and contact junction heating (Joule losses at junctions). A lumped meshing scheme is used to construct a numerical representation for cross-ply and angle-ply orientations of 2-ply prepreg stacks. Heat generation patterns are calculated based on voltage and current conservation laws and verified with induction heating of AS4 carbon fiber-reinforced polyetherimide (AS4/PEI) prepreg stacks. Excellent agreement is found except at very low angle-ply orientations where the predicted heating patterns show significant deviations from the experiment results. A sensitivity analysis is also performed to assess the relationship between heating patterns and material and process paramete...

Hee June Kim

Papers

A Study on the Induction Heating of Conductive Fiber Reinforced Composites

A comparison of oven-cured and induction-cured adhesively bonded composite joints

Development of a Numerical Model to Predict In-Plane Heat Generation Patterns During Induction Processing of Carbon Fiber-Reinforced Prepreg Stacks