Design Optimisation of FRP Universal Connectors

There has been an increased demand for developing special connecting elements for pultruded fibre reinforced plastics (PFRP) structures. The first prototype of a moulded fibre reinforced plastic (FRP) universal connector (UC) was presented to the industry in previous work. The merit of this connector was proven through a full-scale testing program for PFRP beam-to-column connections. In order to develop a series of FRP connections with high structural performance and the lowest possible associated cost, design optimisation techniques must be utilised. For this reason, a design optimisation study on a FRP universal connector was conducted. In evaluating the structural performance of each UC design, finite element analysis was employed. The main objective of the study is to develop an optimum design for the UC by maximising its load carrying capacity and minimising the stress concentration at the critical locations. In order to minimize the number of design variables required for producing the optimum UC, the Taguchi statistical method for quality control was incorporated in this study. In this method, statistically planned experiments are used to identify the settings of the UC design parameters that reduce performance variation. Among the different parameters selected in the study are the UC geometry, composite lay-up, and thickness of the various elements comprising the connector. The results of the analysis indicated that the UC wall thickness, the addition of diagonal webs, and the orientation of the fibres in the webs improve the stiffness significantly. Other design recommandations and conclusions are also presented.