Carbon fiber reinforced plastics (CFRP) have many mechanical properties that are superior to those of conventional structural materials and are becoming more and more widely used. Monitoring the curing process used to produce such composite material is important to ensure the quality of the process, especially for the characterization of residual strains after the material has been manufactured. In this study, we present a tilted fiber Bragg grating (TFBG) sensor used to monitor the curing of CFRP composite materials. The TFBG sensor was embedded into the layers of CFRP laminates to study the curing residual strain of the laminates. The experimental results showed that the curing residual stress was about −22.25 MPa, the axial residual strain was −281.351 με, and lateral residual strain of 89.91 με. The TFBG sensor was found to be sensitive to the curing residual strain of the CFRP, meaning that it has potential for use in applications involving composite curing processes. Moreover, it is indeed possible to improve the properties of composite materials via the optimization and monitoring of their curing parameters.

This paper proposes an optical fiber strain sensor based on packaged long-period fiber gratings (PLPFG) which is fabricated by the micro-electromechanical systems (MEMS) process and packaged with poly-dimethylsiloxane (PDMS) polymer materials. The optical fiber sensor packaged with PDMS improves robustness effectively. The proposed PLPFG sensors have periods of 610, 650, 660 μm and fiber diameter of 48, 60, 72 μm, respectively. The resonance dip of the PLPFG grows when a strain loaded onto the sensor. The results show that the largest strain sensitivity of the PLPFG strain sensor was −0.0652 dB/με from 0–1200 με and the linearity (R2) was 0.9812. Accordingly, the proposed PLPFG sensor has good potential for high-sensitivity strain sensing applications.

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Composite materials are widely used in the aerospace industry and structural engineering owing to their advantageous mechanical properties. The curing monitoring of composite material is important to ensure the quality of the curing process, especially for the characterization of residual strains after manufacturing. In this study, we present a notched long-period fiber grating (NLPFG) with a period of 650 μm and a diameter of 66 μm that can be used in the curing monitoring of composite materials. This NLPFG was embedded into the middle layers of composite materials in order to determine the curing residual stress exhibited by the materials. The experimental results showed that the residual stress was about 107 MPa and the axial residual strain was 1490 με. Therefore, the proposed NLPFG has potential as a strain sensor for composite materials.