Carbon/epoxy laminates and foam‐core sandwich composites are frequently used as engineering materials within the aerospace sector. However, epoxy resin matrix and foam‐core materials are highly flammable. In this work, the thermal behaviors of carbon/epoxy laminates and foam‐core sandwich composites were investigated using thermogravimetric analysis at different heating rates in atmospheric air. The morphological images of specimens and the residue after pyrolysis at different characteristic temperatures were further investigated using scanning electron microscopy. Additionally, thermogravimetric Fourier transform infrared spectroscopy was used to analyze the vapors and gases evolved during the thermal decomposition. It was determined that the pyrolysis reactions of carbon/epoxy laminates and foam‐core sandwich composites consist of three decomposition steps. Furthermore, an increase in the heating rate of each material results in higher initial and final temperatures for each thermal decomposition step. Kinetic parameters for the decomposition for carbon/epoxy composites were estimated using Kissinger, Flynn‐Wall‐Ozawa, and Starink methods, and the corresponding thermodynamic parameters were obtained. Through analysis of the reaction kinetics, it was determined that the pyrolysis reactions of carbon/epoxy composites are not easily activated, requiring significant activation energy, but the series of reactions take place easily once this energy barrier is overcome.

Device-free object tracking provides a promising solution for many localization and tracking systems to monitor non-cooperative objects, such as intruders, which do not carry any transceiver. However, existing device-free solutions mainly use special sensors or active RFID tags, which are much more expensive compared to passive tags. In this paper, we propose a novel motion detection and tracking method using passive RFID tags, named Twins. The method leverages a newly observed phenomenon called critical state caused by interference among passive tags. We contribute to both theory and practice of this phenomenon by presenting a new interference model that precisely explains it and using extensive experiments to validate it. We design a practical Twins based intrusion detection system and implement a real prototype by commercial off-the-shelf RFID reader and tags. Experimental results show that Twins is effective in detecting the moving object, with very low location errors of 0.75 m in average (with a deployment spacing of 0.6 m).

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