Thermoplastic fibre reinforced composites offer a wide range of adjusting the material behaviour by varying material selection, layup and fibre orientation. By default, damping and stiffness of composites are contradictory material properties related to the fibre orientation. Thus, FEA based composite design requires special modelling efforts implying anisotropic damping of the composite as well as fluid-structure-interaction for the oil filling. In contrast, multi-dimensional optimisations for various layups require computationally fast numerical solutions. In this study, a complex but efficient vibro-acoustic modelling approach of a composite oil pan is presented. The FEA model includes a strain energy based modal damping approach for the layerwise accumulation of the anisotropic composite damping as well as a structural representation of the additional mass and damping of the oil filling avoiding fluid modelling. Moreover, the radiated sound power of the component is determined by a structural dynamic steady state FEA using surface velocity based approaches. Next, the scalar optimisation objective, the mean sound power or the total energy within the frequency range, is further estimated by a semi-analytic approximation based on the resonance values. This continuous simulation methodology is further used to design a vibro-acoustically optimised layup for a thermoplastic composite oil pan. The fibre orientation of single layers is chosen assuring a light, stiff and less radiating component.