Entropy based design and topology optimization for multifunctional composite aircraft skins

The research presented in this dissertation investigates the design methodology of a new integrated radar aircraft skin, which serves a multifunctional role by accommodating structural and thermal loads. Mechanically the skin must be capable of handling tensile and shear loads.; The Entropy Generation Minimization (EGM) method is applied to the multifunctional aircraft skin in order to provide a thermodynamic metric for the analysis of different skin material systems. Thermoelectric (TE) devices, sandwiched between the skin and the radar devices for the purpose of harvesting some of the waste heat to be rejected to the ambient, are considered in the analysis. The optimal entropy generation configuration is one that corresponds to the maximum energy harvesting condition, while satisfying tensile and shear running loads. This optimal condition is found to be when the skin is at its thinnest, with a maximum of 65% volume fraction of carbon fiber inclusions. Additionally it is shown that despite increasing the mass of the skin, the overall mission entropy generated decreases.; A topology optimization technique is used to determine the optimal material distribution within the multifunctional skin composite at the 65% volume fraction of inclusion material. A three-dimensional design space is created in which thermal and mechanical loads are applied, and optimized using the Solid Isotropic Microstructures with Penalization (SIMP) method. A weighting variable is introduced to allow for scaling of the incident loads, such that either the thermal or mechanical loading condition may be the dominant load affecting the design space. A thermal dominant loading condition produces a topology representative of a domed structure. A mechanically dominate load results in a 'truss' shaped structure. Novel topologies between these two extreme solutions are realized and presented.; Materials research was conducted on carbon foams to assess their viability as a multifunctional skin material. Pristine foam cubes and foam cubes reinforced with a nano-modified resin were compressed to determine modulus and yield strength values. The Young's modulus was increased up to 3x over the Young's modulus of the pristine foam. The yield strength was increased up to 3.5x over the pristine foam.