Design for manufacture: Cost-estimating model for randomly oriented strand advanced composite aerospace parts

Abstract

This work aimed at developing a parametric cost-estimating model based on physical laws for making three categories of thermoplastic composites structural aerospace parts from discontinuous prepreg randomly oriented strands. The proposed cost model will use Microsoft Excel spreadsheet developed in house which imputes all industrial and academic data for calculating costs elements such as material, labour, energy, machinery, building costs and costs of working capital, overheads and then the total cost per part. This research study focused, on one hand, at estimating the heating costs for experimental and virtual parts by changing the volume and keeping the same process cycle times. The heating power was determined by simulating the process thermal diagram numerically using finite elements COMSOL software and validated by experimental data. On the other hand, the tooling costs were estimated by DFMA software for experimental and virtual moulds by changing the projected area. Then, the heating energy and tooling costs sizing scaling laws were established under linear equation forms limited to the size of platens areas. These linear equations were inputted in an Excel spreadsheet to calculate the cost of new parts, which have not been made yet. The variation of the total cost with the size and the complexity of the part were investigated. The results showed that the calculated heating energy costs of the three experimental randomly oriented strand parts were different due to different geometries of the heating platens and the moulds. For the mould cost, the more complex the form was the higher the cost. For total cost, it was also demonstrated that the manufacturing cost of L-bracket part was higher than that of flat plate and T-shape part due to higher process cycle time.