Methods for microwave melting of fiber mixtures to form composite materials include placing the fiber mixture in a receptacle located in a microwave oven. The methods further include microwave heating the mixture, causing a heat activated compression mechanism to automatically increase compressive force on the mixture, thereby eliminating air and void volumes. The heat activated compression mechanism can include a shape memory alloy wire connecting first and second compression brackets, or one or more ceramic blocks configured to increase in volume and thereby increase compression on the mixture.