In one embodiment, a method for making a high density structural composite includes depositing a plurality of fibrous materials on or adjacent a first plate or surface. A polymer liquid is deposited onto the plurality of fibrous materials to form a composite mixture. A first cyclic pressure is applied onto the composite mixture to compress the composite mixture. In some embodiments, the cyclic pressure may then be reduced to a valley pressure to complete a pressurization cycle. In some instances, the valley pressure may be below atmospheric pressure to induce trapped air and volatile gases to escape from the composite mixture before curing. The pressurization cycle may be repeated. A second pressure, which may be a constant pressure in some embodiments, may be applied to the composite mixture using, in some embodiments, a second plate until the polymer liquid has at least partially cured or partially solidified.