Thickness control of autoclave-moulded composite laminates

Composite materials and especially those made from pre-impregnated (prepreg) material are widely used in the aerospace industry. To achieve the tight assembly dimensional tolerances required, manufacturers rely on additional manufacturing steps like shimming or machining, which generate extra waste, are time-consuming and expensive. Prepreg sheets come naturally with fibre and resin volume content variability that leads manufacturers to guarantee cured ply thicknesses within a typical +/-5% margin of their nominal values. For thick laminates, this can equate to a thickness variability of as much as a few mm. To solve the issue, it is proposed to twin in-situ laser measurements of the uncured prepreg thickness with numerical simulations of the laminate autoclave consolidation and cure process and to adjust the number of additional sacrificial plies in the laminate based on the model predictions. Data for IM7/8552 and IM7/977-3 is presented to demonstrate the potential of the method to reach an almost exact target thickness for flat panels.