Design and strength optimisation of inserts embedded into fibre reinforced laminates

•New compression moulding process for thermoplastic composites with metal inserts.•FE model accurately predicts pull-out strengths for a wide range of geometries.•Multi-objective optimisation method for high strength and low mass inserts. Fibre reinforced plastics have great potential for the design of lightweight structures with high stiffness and strength. However, in practical engineering applications, there is a frequent requirement to join composite parts together or to join composite parts with metallic parts, creating hybrid connections. The ability to join such parts without performance degradation is a challenging task. This paper presents a near-netshape compression moulding manufacturing methodology for direct embedment of lightweight metallic load introduction inserts into composite laminates. The paper investigates the optimal pull-out strength design of these inserts considering a wide range of insert parameters. Extensive experimental characterisation is undertaken with both steel and titanium cone inserts, considering variation of insert diameter, cone height and vertical position within the laminate. The experimental results are used to validate a finite element model, which is then used for multi-objective optimisation and the generation of design charts, considering both maximum strength and minimum weight multi-objective design requirements. For each insert material, a Pareto front is determined, which defines the set of optimal insert geometries related to its vertical position.