Intelligent composites

Intelligent composites are a new class of materials that have shown a lot of promise because of their ability to detect environmental and/or structural changes. This unique sensing ability has attracted a lot of interest in recent years, and scientists and engineers have come up with numerous types and configurations of such materials to fidfil various sensing and structural requirements. 

The concept of intelligent composite seismic wallpaper for the reinforcement, strengthening, monitoring, and management of civil infrastmctures vulnerable to earthquakes has been proposed in the frame of the POLYTECT project. 

M. Leibowitz, J.R. Vinson, Intelligent composites Design and analysis of composite material structures involving piezoelectric material layers. Technical Report 91-54, Center for Composite Materials, University of Delaware, Newark, Delaware, USA (1991)... 

Weder, A., et al., 2012. A novel technology for the high-volume production of intelligent composite structures with integrated piezoceramic sensors and electronic components. Sensors Actuators A 202, 106-110. 

In addition to their role in composites, high performance fibers are also found in coated and laminated textile products, three-dimensional fabric stmctures, multifunctional property improvement, and intelligent or self-adaptive materials. 

The above tests for characterising coating properties necessarily continue to involve a certain amount of empiricism. The intelligent use of these tests, however, has shown that wide variations of physical and electrochemical characteristics of coatings as a function of composition may be obtained, and further, that significant changes in these characteristics, that can be measured before the usual evidence of failure appears, occur upon natural and accelerated ageing. 

In a binary diagram the position of the three-phase line can be calculated utilising a method whereby the step size is changed when a phase boundary is reached. For example, the calculation begins with an alloy in the (a 4- 0) phase held. The temperature is increased by 10°C steps and its composition maintained so that it exists in the (a + 0) phase field. At each new step the stability of the liquid is checked. Once the liquid becomes stable the previous temperature is used as a start point and the temperature step is decreased. This process is repeated with subsequent decreased step sizes until a the temperature is defined within a critical step size. This method is cumbersome and more intelligent searching routines can be used. But in the end the temperature will be defined within a critical step size. Alternatively, the temperature where the activity/chemical potential of A and B in the three phases is equal can be explicitly calculated. 

Overall an intelligent closed-loop system produces more consistent parts because the advancement to the next stage of cure is based on the resin achieving a certain molecular state rather than on time. The advancement of the viscosity and degree of cure is monitored. Final cure is defined by a universal degree of cure. This is a more consistent way to produce composite parts than simply subjecting them to the same time-temperature schedule when batch variations and differences in prefabrication handling are present. 

In summary an FDEMS sensor system can be used to monitor the processing properties in situ during the fabrication process of a composite part. A smart sensor control system can be used to monitor resin properties for reproducability-quality assurance, to ensure fabric impregnation, and to control and optimize the composite fabrication process intelligently through in situ sensor feedback. 

Intelligent Control of Product Quality in Composite Manufacturing... 

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