Multifunctional Materials - Biomimetics: Biologically Inspired Technologies - page 332

12.2.3.4 Healing Summary

A cross-linked polymer with thermally reversible covalent bonds, such as that created by Wudl
et al., offers many attractive attributes. When combined with a medium that distributes heat, such
as a network of resistive heating wires, the healing mechanism may be initiated throughout the
material. The effectiveness of such a system has yet to be fully determined, however, since healing
occurs on the molecular level to reestablish broken covalent bond, there is considerable promise.
Initial results on macro-cracked neat polymer samples show excellent potential that near full
recovery of original strength is possible. Moreover, healing may be carried out multiple times on
the same broken bond. This polymer requires outside intervention to initiate the heating (healing)
process. We are developing self-sensing smart materials to embed in this material, where an
integrated self-sensing, self-healing composite may act autonomously.

12.2.4 Sensing Functionality

The goal is to add information-based properties into multifunctional composites, mimicking
nature's approach to local and global information acquisition, processing, and communication.
Figure 12.28 identifies the necessary three interwoven challenges that must be successfully met in
order to create intelligently sensing composite materials that are:

Aware of their environmental and internal changes; and

.

Can selectively acquire, process, and store or communicate information locally and globally.

.

As is suggested in this figure, integrating sensing functionality into structural materials begins with
the challenge of composite fabrication that seamlessly integrates within the material the necessary
sensing and electronic platforms, without sacrificing the structural attributes of the resulting system.
The next challenge is that the structurally integrated micro-sensors must be able to monitor, interact
with their neighboring sensors, make on-board decisions, and report on the local structural
environment upon request, or in real-time as necessary. And, the final but equally vital challenge
is to create an efficient data handling architecture with local-global processing and communication
algorithms.

Challenges in developing composites with integrated sensing

Composite fabrication to
include integrated sensors
and electronic network:
robustness and
thermo-mechanical issues

Sensors, processing,
and in situ- global
communications

Networks
data handling
architecture and algorithms

Figure 12.28 Three interwoven challenges that must be successfully met in order to create intelligently sensing
composite materials.