KEYWORDS: Composites, Structural health monitoring, Control systems, Nondestructive evaluation, Sensors, Inspection, Software development, Intelligence systems, Data modeling, Systems modeling
Cornerstone Research Group Inc. (CRG) has developed and demonstrated a composite structural solution called
reflexive composites for aerospace applications featuring CRG's healable shape memory polymer (SMP) matrix. In
reflexive composites, an integrated structural health monitoring (SHM) system autonomously monitors the structural
health of composite aerospace structures, while integrated intelligent controls monitor data from the SHM system to
characterize damage and initiate healing when damage is detected. Development of next generation intelligent
controls for reflexive composites were initiated for the purpose of integrating prognostic health monitoring
capabilities into the reflexive composite structural solution.
Initial efforts involved data generation through physical inspections and mechanical testing. Compression after
impact (CAI) testing was conducted on composite-reinforced shape memory polymer samples to induce damage and
investigate the effectiveness of matrix healing on mechanical performance. Non-destructive evaluation (NDE)
techniques were employed to observe and characterize material damage. Restoration of mechanical performance
was demonstrated through healing, while NDE data showed location and size of damage and verified mitigation of
damage post-healing. Data generated was used in the development of next generation reflexive controls software.
Data output from the intelligent controls could serve as input to Integrated Vehicle Health Management (IVHM)
systems and Integrated Resilient Aircraft Controls (IRAC). Reflexive composite technology has the ability to
reduce maintenance required on composite structures through healing, offering potential to significantly extend
service life of aerospace vehicles and reduce operating and lifecycle costs.
Cornerstone Research Group Inc. has developed reflexive composites achieving increased vehicle
survivability through integrated structural awareness and responsiveness to damage. Reflexive
composites can sense damage through integrated piezoelectric sensing networks and respond to damage
by heating discrete locations to activate the healable polymer matrix in areas of damage. The polymer
matrix is a modified thermoset shape memory polymer that heals based on phenomena known as
reptation.
In theory, the reptation healing phenomena should occur in microseconds; however, during
experimentation, it has been observed that to maximize healing and restore up to 85 % of mechanical
properties a healing cycle of at least three minutes is required. This paper will focus on work conducted
to determine the healing mechanisms at work in CRG's reflexive composites, the optimal healing cycles,
and an explanation of the difference between the reptation model and actual healing times.
Aerospace systems stand to benefit significantly from the advancement of reflexive aerostructure
technologies for increased vehicle survivability. Cornerstone Research Group Inc. (CRG) is developing
lightweight, healable composite systems for use as primary load-bearing aircraft components. The
reflexive system is comprised of piezoelectric structural health monitoring systems, localized thermal
activation systems, and lightweight, healable composite structures. The reflexive system is designed to
mimic the involuntary human response to damage. Upon impact, the structural health monitoring system
will identify the location and magnitude of the damage, sending a signal to a discrete thermal activation
control system to resistively heat the shape memory polymer (SMP) matrix composite above activation
temperature, resulting in localized shape recovery and healing of the damaged areas. CRG has demonstrated SMP composites that can recover 90 percent of flexural yield stress and modulus after postfailure
healing. During the development, CRG has overcome issues of discrete activation, structural health monitoring integration, and healable resin systems. This paper will address the challenges associated with development of a reflexive aerostructure, including integration of structural health monitoring, discrete healing, and healable shape memory resin systems.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.