Proposal of an active composite with embedded sensor

Abstract

Though advanced composites with embedded actuator materials such as shape memory alloys and piezo ceramics have been developed as active materials, another one by making use of thermal deformation of composites was proposed and an active laminate was prepared as an example by hot-pressing of aluminum plate as material of high coef®cient of thermal expansion (CTE), uni-directional carbon ®ber reinforced plastics (CFRP) prepreg as low CTE material and electric resistance heater, polymer adhesive ®lm as insulator between them, and copper foils as electrodes. Actuation of this laminate is different from that of bimetal because CTE of the CFRP layer is strongly anisotropic due to directionality of its reinforcement ®ber. As CTEs of the CFRP layer and the aluminum plate in the ®ber direction are quite different from each other though they are close to each other in the transverse direction, smooth and uni-directional actuation becomes possible. In this study, its fundamental performances such as shape change and output force were observed and evaluated, and after establishment of its fabrication, an optical loss type sensor was formed in the active composite, by embedding multiply pre-notched optical ®ber in the CFRP layer and breaking it at the pre-notches under bending, followed by lamination on aluminum plate with adhesive. As the sensing part can be formed inside the matrix without any complicated processes, a robust and low cost sensor is obtained. From the results, it becomes clear that: (1) curvature of the active composite linearly changes as a function of temperature between room temperature and its hot pressing temperature by electric resistance heating of the CFRP layer and cooling, (2) its output force against a ®xed punch during heating from room temperature up to around glass transition temperature of the resin phase almost linearly increases with increasing temperature, (3) the multiply pre-notched, embedded and fractured optical ®ber works as a sensitive sensor for monitoring the curvature of the active composite.

The Development of Active and Sensitive Structural Material Systems

“…The fiber-optic sensor shown in Figure 3 was multiply made in the CFRP layer to enhance total optical loss when the active laminate is actuated [10]. This type of laminate was made as shown in Figure 17.…”

Thermaly Active Structures for Shape Morphing Applications

“…Controlled behaviour composite material (CBCM) [14][15][16][17][18] is a thermal actuator developed ten years ago. There are two different ways to use the CBCM (Figure 1): the first one is called "temperature effect" and the second "gradient effect"; the difference between the two effects is the possibility for the composite structure to bend in one or two directions, respectively.…”

“…Asanuma et al [18] used this solution and presents an active composite made of composite/metal layers. To create the thermal field, a CFRP (unidirectional carbon-fiber-reinforced plastic) connected to a current generator was used.…”

Development of High Performance CFRP/Metal Active Laminates

“…In the case of developing active and smart structural materials, shape memory alloys and piezoelectric ceramics have been mainly used (2), (3) , but Asanuma proposed another effective active material by making use of thermal deformation of CFRP/metal laminates with electric resistance heating of the carbon fibers in the CFRP (4), (5) . An example can be made by laminating a metal plate as a high CTE (coefficient of thermal expansion) material and CFRP prepreg as a low CTE material/in-situ electric heater with a thin insulating layer between them.…”