Novel Curve-Shape Sandwich Composites with Flexible Cores for Rehabilitation of Buried Infrastructure: Experimental and Analytical Studies Considering Geometric Nonlinearity

This paper presents findings from an experiment examining a novel curve-shape sandwich composite made of fiber-reinforced polymer (FRP) facesheets and flexible cores under transverse compressive loading. The curve-shape sandwich composites aim to enhance strength and stiffness while minimizing material use, particularly as liner for rehabilitation of large buried infrastructure like pipes and culverts. The study involved fabricating and testing 24 circular liners with various facesheet-core combinations. Results include deflection measurements, load data, and tensile strain values at different points on the liners. The stiffness of each sandwich specimen was compared to theoretical predictions based on composite facesheet behavior. Notably, bulkermat cores demonstrated superior stiffness and strength compared to three-dimensional (3D) woven fabric cores, exhibiting higher composite action. In contrast, solid-wall liners exhibited greater deformations than sandwich liners. To predict these significant deformations, an iterative analytical model was developed, accounting for geometric nonlinearity. This model accurately predicted test data prior to any material nonlinearity, such as facesheet or core failure. Additionally, the model was used to perform a parametric analysis, exploring various liner characteristics, including diameter, FRP layers, core thickness, and liner shape.