Bruce K. Fink

Bio: Bruce K. Fink is an academic researcher from University of Delaware. The author has contributed to research in topics: Heat generation & Induction heating. The author has an hindex of 5, co-authored 5 publications receiving 132 citations.

A local theory of heating in cross‐ply carbon fiber thermoplastic composites by magnetic induction

Abstract: For joining and repair of continuous fiber thermoplastic composites, induction heating has been viewed a strong candidate. Induction heating employs an applied alternating magnetic field, which induces a rotational emf in a grid of conductive carbon fibers, which are then used to carry resulting currents. In continuous carbon fiber crossply composites the available paths for “eddy current” loops are along the network of conductive carbon fibers. For this to occur, an electrical transfer must take place between crossing fibers in adjacent plies. Tests involving variable thicknesses of interply neat film layers have been performed to provide insight into the mechanisms taking place. These tests indicate that the primary mechanism for heating in such laminates is dielectric losses in the polymeric region between fibers in adjacent planes that form the conductive loop. Therefore, heating is not uniform in such composites despite a uniform magnetic flux. Heating patterns were viewed using liquid crystal materials and E-type thermocouples. Several factors leading to nonhomogeneous thermal distributions have been considered, including current density effects, internal emf cancellation, and rotational field effects. Global and local considerations are addressed, a localized model is proposed, and the corresponding theory is developed qualifying the early results. Additional testing has supported the theory.

Experimental verification of models for induction heating of continuous-carbon-fiber composites

Abstract: Heating of continuous-carbon-fiber-reinforced polymers (CFRPs) by the application of an alternating magnetic field has been shown to be due to dielectric losses in the polymer. Models that predict thermal generation in these composites are input to a finite element heat transfer analysis, providing the predicted transient thermal profile in the plane of the laminate. The validity of the global thermal generation model is established through an experimental test matrix in which various specimen configurations are evaluated and compared with theoretical predictions of transient surface temperatures.

The Influence of Moisture on Dielectric Behavior of Poly-Etheretherketone/ Carbon Fiber Composites

Abstract: An analysis of local and global mechanisms of heat generation and distri bution in carbon-fiber-based composites subjected to an alternating magnetic field has shown that heating is dependent upon the dielectric properties of the polymer matrix. These properties were investigated as functions of temperature, frequency and moisture content. The results indicated little dependence of the dielectric constant on temperature or frequency, while the loss tangent exhibited a substantial dependence on both frequency and temperature. A substantial dependence of loss tangent on moisture content in PEEK was found. Significant increases in loss tangent corresponding to small increases in mois ture content are exemplified by a parametric analysis of our induction heating model.

Processing of fibre reinforced thermoplastic composites

Abstract: With the advent of high performance thermoplastic polymers, structural applications for thermoplastic composites are increasing rapidly. Thermoplastic matrix composites possess distinct advantages vis-a-vis thermoset matrix composites in terms of recyclability, high specific strength and specific stiffness, corrosion resistance, enhanced impact toughness, cost effectiveness, and flexibility of design. Since 1990s, the number of material forms and combinations in fibre reinforced thermoplastic polymers has increased exponentially, thereby expanding application avenues in transportation, automotive, mass transit, marine, aerospace, military and construction sectors. In this paper we review the state of the art in processing of fibre reinforced thermoplastics. We start with a brief description of thermoplastic polymers used in structural applications followed by material forms and methods of impregnation of the reinforcement with polymer. Long fibre based processing methods are described next. A desc...

Induction welding of thermoplastic composites—an overview

Abstract: 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.

The heating of polymer composites by electromagnetic induction – A review

Abstract: 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.

Induction heating of continuous carbon-fibre-reinforced thermoplastics

Abstract: This paper addresses the experimental investigation of induction heating of continuous carbon-fibre reinforced thermoplastics. The influence of the process parameters electromagnetic frequency, generator power, distance between induction coil and laminate, coil geometry and laminate lay-up on the heating rate and the heat distribution have been investigated in stationary experiments. It was found that all investigated parameters have significant influence on the heating behaviour and that a quadratic dependence is dominating. Heat is only generated when closed fibre loops exist, through which current can flow. The quality of the fibre junctions in a laminate, especially the contact length, was found to be of major importance. Thus, for example laminates with unidirectional fibre reinforcement, which do not contain fibre junctions, cannot be heated. Experimental evidence has shown that induction heating of carbon-fibre-reinforced thermoplastics is based on Joule losses.

Curing Methods for Advanced Polymer Composites - A Review:

Abstract: Advanced polymer composites have obtained great application interest in a number of demanding aerospace, wind energy, automotive, infrastructure, and consumer applications. Great varieties of curin...