We are now developing an impact damage detection (IDD) system for composite airframe structures. The basic
technologies of IDD system were developed and demonstrated using a composite structure with embedded small-diameter
optical fiber sensors by Authors in FY2002. IDD system consists of a composite structure with installed optical
fiber sensors and a monitoring measurement system. To get the prospect of aircraft application of IDD system is a target
of this development. To investigate the durability of embedded optical fibers and composites, cyclic loading test is
conducted using composite coupon specimens with embedded small-diameter optical fibers. The evaluation of the
system by using composite substructures is also conducted to proceed towards product. This paper presents the
development target, our technology, test method, test result and future task.
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
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.
There is a growing demand for lightweight structures in aircraft systems for realizing energy and cost savings. The authors are developing a new lightweight grid structure for aircraft applications equipped with a health monitoring system utilizing fiber Bragg grating (FBG) sensors. The grid structure has a very simple path for stress, which is easily detected by FBG sensors embedded in the ribs. In this research, the difference in the strain distributions before and after damage to the grid structure was evaluated analytically, and a damage detection method was established. The correspondence between damage detection ability and damage tolerance design strength was clarified. Furthermore, the damage tolerance design method was established based on the evaluation of residual strength corresponding to the detected damage level of rib. Next, the prototype of a highly reliable grid structure embedded with FBG sensors was manufactured, and the damage detection ability was experimentally verified. The panel size of the specimen was 525 x 550 mm and 29 FBG sensors were embedded at the center of the panel. Load was applied on the grid panel, and the strain distribution was measured by the multipoint FBG sensors. The artificial damage introduced in one rib of the specimen and the position of the damage, were successfully detected by comparing the strain distributions before and after the introduction of the damage.
The Japanese Smart Material and Structure System Project started in 1998 as five years' program that funded by METI (Ministry of Economy, Trade and Industry) and supported by NEDO (New Energy and Industrial Technology Development Organization). Total budget of five years was finally about 3.8 billion Japanese yen. This project has been conducted as the Academic Institutions Centered Program, namely, one of collaborated research and development among seven universities (include one foreign university), seventeen Industries (include two foreign companies), and three national laboratories. At first, this project consisted of four research groups that were structural health monitoring, smart manufacturing, active/adaptive structures, and actuator material/devices. Two years later, we decided that two demonstrator programs should be added in order to integrate the developed sensor and actuator element into the smart structure system and verify the research and development results of above four research groups. The application target of these demonstrators was focused to the airplane, and two demonstrators that these shapes simulate to the fuselage of small commercial airplane (for example, Boeing B737) had been established. Both demonstrators are cylindrical structures with 1.5 m in diameter and 3 m in length that the first demonstrator has CFRP skin-stringer and the second one has CFRP skin. The first demonstrator integrates the following six innovative techniques: (1) impact monitoring using embedded small diameter optical fiber sensors newly developed in this program, (2) impact monitoring using the integrated acoustic emission (AE) systems, (3) whole-field strain mapping using the BOTDR/FBG integrated system, (4) damage suppression using embedded shape memory alloy (SMA) films, (5) maximum and cyclic strain sensing using smart composite patches, and (6) smart manufacturing using the integrated sensing system. The second one is for demonstrating the suppression of vibration and acoustic noise generated in the composite cylindrical structure. In this program, High-performance PZT actuators/sensors developed in this program are also installed. The whole tests and evaluations have now been finished. This paper presents the outline of demonstrator programs, followed by six presentations that show the detail verification results of industrial demonstration themes.
The Japanese Smart Material and Structure System Project started in 1998 and has been developing several key sensor and actuator elements. This project consists of four research groups that consist of structural health monitoring, smart manufacturing, active/adaptive structures, and actuator materials/devices. In order to integrate the developed sensor and actuator elements into a smart structure system and show the validity of the system, two demonstrator programs have been established. Both demonstrators are CFRP stiffened cylindrical structures with 1.5 m in diameter and 3 m in length. The first demonstrator integrates the following six innovative techniques: (1) impact damage detection using embedded small-diameter optical fiber sensors newly developed in this program, (2) impact damage detection using the integrated acoustic emission (AE) system, (3) whole-field strain mapping using the BOTDR/FBG integrated system, (4) damage suppression using embedded shape memory alloy (SMA) foils, (5) maximum and cyclic strain sensing using smart composite patches, and (6) smart manufacturing using the integrated sensing system. The second one is for demonstrating the suppression of vibration and acoustic noise generated in the composite cylindrical structure. High-performance PZT actuators developed in this program are also installed. The detailed design of the demonstrator was made and the testing program has been planned to minimize the time and the cost for the demonstration. The present status of the demonstrator program is presented, including the success and difficulty in the on-going program.