Composite Patch Repair Numerical Simulations

Abstract

Recent developments in the composite patch repair techniques have aimed to overcome the limitations of classic repairs of corroded steel plates through welding which consists of cropping and renewing of steel plates. Welding involves hot work which significantly interrupts the operation of vessels, particularly for Floating Offshore Production, Storage and Offloading (FPSO) vessels. The Joint Industry Project (JIP) StrengthBond Offshore (SBO) developed a robust methodology for the design assessment of composite patch repairs on corroded steel structure. Several experiments were performed on specimens to determine the failure of composite/steel assembly and numerical simulation were conducted and compared results with experiments. The present study is conducted under the DuraBond Joint Industry Project (JIP) to develop structurally optimized and computationally efficient models that are well suited for the industrial applications. Based on the reference model from SBO, 4 composite patch configurations have been developed by focusing on the hybrid modelling approach and investigated through finite element simulations on FEMAP Nastran. To capture the behavior of steel – composite interface in each model, cohesive zone modelling (CZM) approach is adopted. This method precisely simulates the damage initiation and propagation under the opening and the shear modes by performing tensile and bending tests separately. Cohesive damage patterns are observed and compared with the reference model which shows good correlation. Force vs displacement curves are also obtained to analyze the behavior of each model w.r.t reference model. Among the 4 optimized patch models, patch 2 model has shown consistent and balanced performance based on simulation results. It has provided precise structural response while significantly reducing the computational cost as compared to reference model, making it the most practical candidate for full scale modelling and further industrial use. Overall, the developed modelling strategy supports future applications in large scale composite patch repairs of corroded steel structures in offshore conditions and aligns with practical objectives of industrial feasibility and standardization.