When the thermoplastic composites reach the service limits during the service, the recovery and utilization are the key concerns. Meanwhile, the improvement of strength, toughness and durability of epoxy resin is the effective method to prolong the service life of materials and structures. In the present paper, three kinds of thermoplastic resins (polypropylene-PP, polyamide 6-PA6 and polyether-ether-ketone-PEEK) and composites (carbon fiber-PEEK, glass fiber-PA6 and glass fiber-PP) were adopted as the fillers to reinforce and toughen the epoxy resin (Ts). The mechanical, thermal and microscopic analysis were conducted to reveal the performance improvement mechanism of Ts. It can be found that adding thermoplastic resin and composite fillers at the low mass ratio of 0.5~1.0% brought about the maximum improvement of tensile strength (7~15%), flexural strength (7~15%) and shear strength (20~30%) of Ts resin. The improvement mechanism was because the addition of thermoplastic fillers can prolong the cracking path and delay the failure process through the load bearing of fiber, energy absorption of thermoplastic resin and superior interface bonding. In addition, the thermoplastic composite had better enhancement effect on the mechanical/thermal properties of Ts resin compared to thermoplastic resin. When the mass ratio was increased to 2.0~3.0%, the agglomeration and stress concentration of thermoplastic filler in Ts resin appeared, leading to the decrease of mechanical and thermal properties. The optimal addition ratios of thermoplastic resin were 0.5~1.0% (PEEK), 1.0~2.0% (PA6) and 0.5~1.0% (PP) to obtain the desirable property improvement. In contrast, the optimal mass ratios of three kinds of composite were determined to be 0.5~1.0%. Application prospect analysis indicated adding the thermoplastic resin and composite fillers to Ts resin can promote the recycling and reutilization of thermoplastic composites and improve the performance of Ts resin, which can be used as the resin matrix, interface adhesive and anti-corrosion coating.

Phase retrieval algorithm is an important part of optic‐fiber interferometry system. In this article, drift of the retrieved signal caused by the time delay difference between two interference signals from asymmetric 3 × 3 coupler is theoretically analyzed, and a compensation algorithm to solve this problem is proposed. Through simulation and experiment in real sensing system, the compensation algorithm can effectively eliminate the signal drift induced by the time delay difference, and enhance the accuracy of the signal in real sensing system.

In this article, multi‐time reflection phenomenon induced by fiber connector at the connection point of device module in engineering applied all‐fiber long‐distance distributed vibration sensing system is analyzed and discussed. Despite the application of phase generated carrier (PGC) technology, this multi‐time reflection phenomenon severely degrades the performance of the system. Through theoretical analysis and experiments on the basis of PGC technology, it is found that the influence of multi‐time reflection on the system can be suppressed by selecting appropriate modulation frequency according to the position of the reflection point, and the distortion of the phase retrieved signal is effectively eliminated.

No abstract