Life cycle health monitoring technology for composite airframe structures based on strain mapping is proposed. It
detects damages and deformation harmful to the structures by strain mapping using fiber Bragg grating (FBG) sensors
through their life cycles including the stages of molding, machining, assembling, operation, and maintenance. In this
paper, we firstly carried out a strain monitoring test of CFRP mock-up structure through the life cycle including the stage
of molding, machining, assembling, and operation. The experimental result confirms that the strain which arises in each
life cycle stage can be measured by FBG sensors embedded in molding stage and demonstrates the feasibility of life
cycle structural health monitoring by using FBG sensors. Secondly, we conducted the strain monitoring test of CFRP
scarf-repaired specimen subject to fatigue load. FBG sensors were embedded in the scarf-repaired part of the specimen
and their reflection spectra were measured in uni-axial cyclic load test. Strain changes were compared with the pulse
thermographic inspection. As a result, strain measured by FBG sensors changed sensitively with debonded area of repair
patch, which demonstrates that the debondings of repair patches in scarf-repaired composites due to fatigue load can be
detected by FBG sensors.
This paper proposes structural health monitoring technology based on the strain mapping of composite airframe
structures through their life cycles by FBG sensors. We carried out operational load tests of small-sized mockup
specimens of CFRP pressure bulkhead and measured the strain by FBG sensors. In addition, we confirmed strain change
due to stiffener debondings. Moreover, debonding detectability of FBG sensors were investigated through the strain
monitoring test of CFRP skin-stiffener panel specimens. As a result, the strain distribution varied with damage
configurations. Moreover, the change in strain distribution measured by FBG sensors agrees well with numerical
simulation. These results demonstrate that FBG sensors can detect stiffener debondings with the dimension of 5mm in
composite airframe structures.
The objective of this work is to develop a system for monitoring the structural integrity of composite airframe structures by
strain mapping over the entire lifecycle of the structure. Specifically, we use fiber Bragg grating sensors to measure strain
in a pressure bulkhead made of carbon fiber reinforced plastics (CFRPs) through a sequence of lifecycle stages (molding,
machining, assembly, operation and maintenance) and detect the damage, defects, and deformation that occurs at each stage
from the obtained strain distributions. In previous work, we have evaluated strain monitoring at each step in the FRP
molding and machining stages of the lifecycle. In the work reported here, we evaluate the monitoring of the changes in
strain that occur at the time of bolt fastening during assembly. The results show that the FBG sensors can detect the
changes in strain that occur when a load is applied to the structure during correction of thermal deformation or when there
is an offset in the hole position when structures are bolted together. We also conducted experiments to evaluate the
detection of damage and deformation modes that occur in the pressure bulkhead during operation. Those results show that
the FBG sensors detect the characteristic changes in strain for each mode.
Next generation space telescopes, which are currently being developed in the US and Europe, require large-scale lightweight
reflectors with high specific strength, high specific stiffness, low CTE, and high thermal conductivity. To meet
budget constraints, they also require materials that produce surfaces suitable for polishing without expensive overcoatings.
HB-Cesic® - a European and Japanese trademark of ECM - is a Hybrid Carbon-Fiber Reinforced SiC composite
developed jointly by ECM and MELCO to meet these challenges. The material's mechanical performance, such as
stiffness, bending strength, and fracture toughness are significantly improved compared to the classic ECM Cesic®
material (type MF). Thermal expansion and thermal conductivity of HB-Cesic® at cryogenic temperatures are now
partly established; and excellent performance for large future space mirrors and structures are expected.
This paper will present the whole manufacturing process of such a space mirror starting from the raw material
preparation until the polishing of the optic including cryo testing .
The letters "HB" in HB-Cesic® stand for "hybrid" to indicate that the C/C raw material is composed of a mixture of
different types of chopped, short carbon-fibers.
Next generation space telescopes, which are currently being developed in the US and Europe, require large-scale light-weight
reflectors with high specific strength, high specific stiffness, low CTE, and high thermal conductivity. To meet
budget constraints, they also require materials that produce surfaces suitable for polishing without expensive over-coatings.
HB-Cesic - a European and Japanese trademark of ECM - is a Hybrid Carbon-Fiber Reinforced SiC composite
developed jointly by ECM and MELCO to meet these challenges. The material's mechanical performance, such as
stiffness, bending strength, and fracture toughness are significantly improved compared to the classic ECM Cesic
material (type MF). Thermal expansion and thermal conductivity of HB-Cesic at cryogenic temperatures are now partly
established; and excellent performance for large future space mirrors and structures are expected.
This paper presents the design and manufacturing of an 800-mm mirror for space application, starting with the C/C raw
material preparation to the finishing of the components, including the polishing of the mirror.
The letters "HB" in HB-Cesic stand for "hybrid" to indicate that the C/C raw material is composed of a mixture of
different types of chopped, short carbon-fibers.
There is a growing demand in recent years for lightweight structures in aircraft systems from the viewpoints of energy
and cost savings. The authors have continued development of the Highly Reliable Advanced Grid Structure (HRAGS)
for aircraft structure. HRAGS is provided with health monitoring functions that make use of Fiber Bragg Grating (FBG)
sensors in advanced grid structures. To apply HRAGS technology to aircraft structures, a full-scale demonstrator
visualizing the actual aircraft structure needs to be built and evaluated so that the effectiveness of the technology can be
validated. So the authors selected the wing tip as the candidate structural member and proceeded to design and build a
demonstrator. A box-structure was adopted as the structure for the wing-tip demonstrator, and HRAGS panels were used
as the skin panels on the upper and lower surfaces of the structure. The demonstrator was designed using about 600 FBG
sensors using a panel size of 1 x 2 m. By using the demonstrator, damage detection functions of HRAGS system were
verified analytically. The results of the design and evaluation of the demonstrator are reported here.
There is a growing demand for lightweight structures in aircraft systems for energy and cost savings. The authors have
therefore continued development of the Highly Reliable Advanced Grid Structure (HRAGS) with the aim of application
of the same to aircraft. HRAGS is provided with health monitoring functions that make use of Fiber Bragg Grating
(FBG) sensors in advanced grid structures, which have been the focus of attention in recent years as lightweight
structures. It is a new lightweight structural concept that enables lighter weight to be obtained while maintaining high
reliability.
This report describes the tests and evaluation of the Proto System conducted to verify experimentally the concept of the
highly reliable advanced grid structure. The Proto System consists of a skin panel embedded with 29 FBG sensors and a
wavelength detection system. The artificial damage to the skin panel of the specimen was successfully detected by
comparing the strain distributions before and after the introduction of the damage measured by FBG sensors. Next, the
application of HRAGS to the wing tip was studied. The results of the studies above are reported here.
One of the key technologies for next generation space telescope with a large-scale reflector is a material having high specific strength, high specific stiffness, low coefficient of thermal expansion and high coefficient of thermal conductivity. Several candidates such as fused silica, beryllium, silicon carbide and carbon fiber reinforced composites have been evaluated. Pitch-based carbon fiber reinforced SiC composites were developed for the SPICA space telescope mirror to comply with such requirements. Mechanical performance such as bending stiffness, bending strength and fracture toughness was significantly improved. Evaluation procedures of thermal expansion and thermal conductivity behavior at cryogenic temperatures (as low as 4.5K) were established and excellent performance for the SPICA mirror was demonstrated.
Future large aperture telescope projects will require very lightweight mirrors that can be produced at significantly lower cost and faster production times than currently possible. Tailorable, low thermal expansion composite materials offer an attractive path to achieve these goals. Application of carbon/carbon composites is particularly attractive as these materials do not exhibit the moisture-absorption-related expansion problems observed in typical resin matrix composites. The National Astronomical Observatory of Japan and Mitsubishi Electric Corporation are collaborating to develop materials and surface finishing technologies to enable future carbon/carbon composite mirror applications. Material processing techniques for improved substrate surface finish have been developed. An innovative surface finish approach involving high precision machining of a metal layer applied to the mirror surface has also been developed. As a result, 150mm diameter C/C spherical mirror with honeycomb sandwich structure was successfully demonstrated.
One of the key technologies for next generation space telescope with a large-scale reflector is a material having high specific strength, high specific stiffness, low coefficient of thermal expansion and high coefficient of thermal conductivity. Several candidates such as fused silica, beryllium, silicon carbide and carbon fiber reinforced composites have been evaluated. Pitch-based carbon fiber reinforced SiC composites were developed for the SPICA space telescope mirror to comply with such requirements. Mechanical performance such as bending stiffness, bending strength and fracture toughness was significantly improved. Evaluation procedures of thermal expansion and thermal conductivity behavior at cryogenic temperatures (as low as 4.5K) were established and excellent performance for the SPICA mirror was demonstrated.
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.