Standard Article

The HELP-Layer® System

Systems and System Design

Examples of Systems

  1. Michel B. Lemistre

Published Online: 15 SEP 2009

DOI: 10.1002/9780470061626.shm100

Encyclopedia of Structural Health Monitoring

Encyclopedia of Structural Health Monitoring

How to Cite

Lemistre, M. B. 2009. The HELP-Layer® System. Encyclopedia of Structural Health Monitoring. .

Author Information

  1. Ecole Normale Supérieure de Cachan, Laboratoire SATIE/CNRS, Cachan, France

Publication History

  1. Published Online: 15 SEP 2009


The HELP-Layer® system, based on the interaction between an electromagnetic field and a material, is particularly suited to composite materials. This technique allows the main damages inside composites such as carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP) to be localized and characterized. This technique, which can be fully embedded, is based on the local measurement of the electric field induced by electric excitation (GFRP) or magnetic induction (CFRP). All damages inducing a local variation of electric conductivity and/or dielectric permittivity of a composite material can be detected and characterized by analyzing the local disturbance of the electric field (contrast). Consequently, this technique allows detection of some damages having nonmechanical origin such as liquid ingress (e.g., water, oil, fuel) or small burns generated by electric sparks (e.g., short circuits, lightning impacts), which are barely detectable by the more classical methods such as ultrasonic analysis.

After a short recall of the principle of this technique, this article describes the technology used, the simulation method, and the algorithm developed, allowing to solve the inverse problem. Several examples of damages detected in GFRP and CFRP materials are given.


  • dielectric substrate;
  • electrical characterization;
  • electrical conductivity;
  • electromagnetic field;
  • electromagnetic sensors;
  • liquid ingress;
  • magnetic induction;
  • SHM;
  • pyrolysis;
  • smart materials;
  • inverse problems