Strain monitoring in glass fiber reinforced composites embedded with carbon nanopaper sheet using Fiber Bragg Grating (FBG) sensors

A novel approach has been developed to fabricate multifunctional nanocomposites using carbon nanopaper sheets. In this study, vapor grown carbon nanofibers are pre-formed as carbon nanopaper sheet. The carbon nanopaper sheet had a porous structure with highly entangled carbon nanofibers. The as-prepared carbon nanopaper sheet was integrated into the laminates through vacuum-assisted resin transfer molding (VARTM) process. To study the integrity of the hybrid nanocomposites, Fiber Bragg Grating (FBG) sensors were embedded into laminated composites. Two types of composite specimens were fabricated to study the characteristics of strain distribution between different layers. The inter-layer strains of the laminates with carbon nanopaper sheet under static bending loads were measured, indicating that carbon nanopaper sheet was fully integrated to the laminates. A tensile test of the laminates with carbon nanopaper sheet as surface layer was conducted, indicating a good bonding between carbon nanopaper sheet and baseline laminates. In addition, scanning electron microscopy (SEM) was used to investigate the impregnation of carbon nanopaper by the resin during the VARTM process. The SEM images show that a complete penetration of the resin through carbon nanopaper was achieved. Therefore, there was a good structural integrity of carbon nanopaper sheet with the laminates.