DEVELOPMENT OF A HIGH-PERFORMANCE INTRALAMINAR-HYBRID COMPOSITE MATERIAL

An innovative dual-fiber, hybrid composite material has been developed for the purpose of increasing the structural efficiency of composite airframe materials. The material combines boron fibers and carbon fibers to take advantage of the high compression strength and modulus of boron fiber and the high tensile strength and modulus of carbon Fiber. It was recognized that small-diameter carbon Fibers (5 microns) would nest between boron fibers because the boron fibers are 20 times larger in diameter. This nesting can theoretically increase fiber volume to 95% of the total material volume, which can result in a significant increase in stiffness and strength. The concept was initially demonstrated by manually combining boron/epoxy prepreg tape with carbon/epoxy. Later, hybrid prepreg was manufactured using a standard preimpregnation operation. Coupons were fabricated and tested to evaluate the new material in tension, compression, and shear. It was concluded that significant increases in compression strength and modulus were achieved. Tests to evaluate corrosion resistance and the effect of thermal cycling were also performed. Preliminary producibility and structural performance were evaluated by fabricating and testing hat-section stringers reinforced with the new material. No significant drawbacks were found and thus it is concluded that this innovation is a potentially viable structural composite material that can reduce weight over conventional composites in some applications.