Modeling and Implementation of VARTM for Civil Engineering Applications

摘要

The use of composite materials in civil engineering applications has been growing at a fast pace for the last decade. Design and building codes for composite structures have been written and approved to a point where consulting companies across the United States and abroad are applying in practice. The technology has been implemented in primary and secondary structural members for design and retrofit. It has also been demonstrated that the use of composites in combination with conventional construction materials has a synergetic effect that can be exploited positively. Processing of composite materials in the field has proven to be a challenge for the construction industry. Thermoset resins, mainly vinyl ester and epoxies pose a safety hazard for workers due to volatile emissions, long curing times, exotherm issues, and proper handling on site. In the case of structural retrofitting and rehabilitation, Vacuum Assisted Resin Transfer Molding (VARTM) is a processing technology that belongs to the liquid molding family of processes and is still under development for civil engineering applications. In order to successfully implement VARTM in the field, processing parameters such as - amount of resin, curing times, filling time, and permeability of the fibers need to be calculated effectively before attempting to repair a structural member. In the present work we have used a finite element (FE) based software, RTM-Worx (Koorevaar, 2002) to simulate liquid molding processes useful processing guidelines for in-field applications. This paper addresses the FE analysis of VARTM and experimental validation for two large-scale scenarios representing infrastructure applications. First, the infusion of an autoclaved aerated concrete (AAC) beam wrapped with 'carbon fabric is simulated and compared to the experimental results. Second, the use of VARTM on a full scale high strength concrete T-bulb girder reinforced with unidirectional carbon fabric is simulated and compared to on-site implementation. The results show excellent agreement between the RTM-Worx generated resin flow information and the experiments for both the AAC and the T-bulb girder application.