Hybrid Titanium Composite

In the realm of aerospace design and performance, there are few boundaries in the never-ending drive for increased performance. This thirst for ever-increased performance of aerospace equipment has driven the aerospace and defense industries into developing exotic, extremely highperformance composites that are pushing the envelope in terms of strength-to-weight ratios, durability, and several other key measurements. To meet this challenge of ever-increasing improvement, engineers and scientists at NASA-Langley Research Center (NASA-LaRC) have developed a high-temperature metal laminate based upon titanium, carbon f i h , and a thermoplastic resin. This composite, known as the Hybrid Titanium Composite Laminate, or HTCL, is the latest chapter in a significant, but relatively short, history of metal laminates. During the mid-l%O’s, Kaufinan [I] showed that it was possible to improve the Eracture toughness of aluminum by laminating thin plies of aluminum togher. During the latter half of the 1970’9, Johnson and colleagues [2,3 ] demonstrated that adhesively laminating thin aluminum plies together would dramatidy improve the fatigue resistance along with improving the crack growth resistance. In the early 1980’9, Johnson followed upon his earlier findings to show that adhesively laminated titanium plies improved fiacture toughness by almost 40??i, increased fatigue life by an order of magnitude, and reduced through-the-thickness crack growth rates by 20% over an equivalent monolithic titanium plate. [4] The next advancement in the history of metal laminates was made at Delft University, the Netherlands, in conjunction with Alcoa. In the mid 1980’s they produced the A W L family of fiber-reinforced metal laminates. The ARALL laminates included aramid fibers in the adhesive bondline between the aluminum plies, further improving the mechanical properties of the laminate.[5,6] The HTCL family of metal laminates took the concept of adding fibers to the adhesive bondline and applied it to the high-temperature regime of supersonic flight. The high temperatures found in supersonic flight necessitate the use of titanium rather than aluminum, and the substitution of Fig. 1 Schematic of a typical HTCL construction