Advanced spray multiple layup process for quality control of sprayed FRP composites used to retrofit concrete structures

Thus far, the typical spray layup process for fabricating sprayed fiber-reinforced polymer (FRP) composites has entirely depended on the know-how and experience of skilled operators in the marine and commercial composite industry. However, there are some limitations on quality control of these retrofit materials by a typical spray layup process, which are as follows: a limited range of fiber loadings in volume and partial defects by the inconsistent thickness of the layer. To overcome these limitations, this study proposes an advanced spray multiple layup process based on a modified gun-calibration technique in conjunction with spray technical skills proposed by the American Composites Manufactures Association. In detail, practical spray skills were adopted to maintain a consistent thickness of the retrofit materials. An advanced gun-calibration technique was suggested to control the various volume fractions of the fibers. Then, following the proposed spray multiple layup process, sprayed FRP laminates were fabricated. Finally, quantitative tests measuring the thickness, volume fraction of the fibers, and mechanical properties of the final laminates were conducted to assess the feasibility of the proposed process as a quality-control method for retrofit materials.