Question: why is fiberglass and carbon composite material in the Saqr models stealthy?
Context: Carbotanium is a patented composite material invented by Modena Design, the carbon composite manufacturing and consultancy arm of the Italian car company Pagani.  It is a combination of beta titanium alloy with advanced carbon composites, having a matched yield strength and moduli of elasticity ratio.  When the combination is adhesively bonded both parts will approach maximum yield strength and fail at a similar amount of total strain.  The titanium and carbon composites are combined by first abrading the titanium to be bonded, coating the titanium with platinum, aging the titanium, spraying primer on the coated titanium, applying adhesive to the primer side of the titanium and then applying the carbon to the adhesive.  This allows the carbon composite to bond securely to the titanium.  This composite uses the best properties of each component, the combination having a better set of properties than either part.  This material is both strong and light. Fiberglass reinforced plastic grating (also known as FRP grating, glass reinforced plastic grating or fiberglass grating) is a composite material manufactured by combining a matrix of resin and fiberglass.  Fiberglass grating does not corrode like steel grating and is therefore used in corrosive environments to reduce maintenance costs.  It is used in a variety of applications including walkways and overhead platforms.  FRP grating is a structural product that can be weight-bearing between spans. Saqr (meaning: "Falcon") is the name of a line of Unmanned aerial vehicles produced by the King Abdulaziz City for Science and Technology for the government of Saudi Arabia.  s of 2014 , three models had been developed: Saqr 2, Saqr 3 and Saqr 4.  All three models are manufactured from fiberglass and carbon composite material, making them lightweight and stealthy.  The Saudi government has developed the craft for research purposes, and the units are equipped with cameras for aerial photography.  According to Prince Turki bin Saud bin Mohammed, the Saqr-1 has a range of more than 2,500 km and can remain airborne for more than 24 hours.  The UAV flies at an average altitude of 20,000 feet. A void is a pore that remains unoccupied in a composite material.  A void is typically the result of an imperfection from the processing of the material and is generally deemed undesirable.  Because a void is a non-uniformity in a composite material, it can affect the mechanical properties and lifespan of the composite.  Voids can act as a crack nucleation site as well as allow moisture to penetrate the composite and contribute to anisotropy of the composite .  This is an issue because crack formation and propagation can create unpredictable behavior in the laminate.  For aerospace applications, a void content of approximately 1% is appropriate for performance while other grades of composites can have between 3%-5% void content.  A small change in the percentage of void content may not seem like a large problem however for a loaded carbon fiber laminate composite, a 1%-3% increase in void content can reduce the mechanical properties of the composite by up to 20% Void content in composites is represented as a ratio, also called void ratio, where the volume of voids, solid material, and bulk volume are taken into account.  Void ratio can be calculated by the formula below where e is the void ratio of the composite, V is the volume of the voids, and V is the volume of the bulk material. Carbon fiber reinforced polymer, carbon fiber reinforced plastic or carbon fiber reinforced thermoplastic (CFRP, CRP, CFRTP or often simply carbon fiber, carbon composite or even carbon), is an extremely strong and light fiber-reinforced plastic which contains carbon fibers.  The spelling 'fibre' is common in British Commonwealth countries.  CFRPs can be expensive to produce but are commonly used wherever high strength-to-weight ratio and rigidity are required, such as aerospace, automotive, civil engineering, sports goods and an increasing number of other consumer and technical applications. Fiber volume ratio is an important mathematical element in composite engineering.  Fiber volume ratio, or fiber volume fraction, is the percentage of fiber volume in the entire volume of a fiber-reinforced composite material.  When manufacturing polymer composites, fibers are impregnated with resin.  The amount of resin to fiber ratio is calculated by the geometric organization of the fibers, which affects the amount of resin that can enter the composite.  The impregnation around the fibers is highly dependent on the orientation of the fibers and the architecture of the fibers.  The geometric analysis of the composite can be seen in the cross-section of the composite.  Voids are often formed in a composite structure throughout the manufacturing process and must be calculated into the total fiber volume fraction of the composite.  The fraction of fiber reinforcement is very important in determining the overall mechanical properties of a composite.  A higher fiber volume fraction typically results in better mechanical properties of the composite. Effective medium approximations or effective medium theory (sometimes abbreviated as EMA or EMT) pertains to analytical or theoretical modeling that describes the macroscopic properties of composite materials. EMAs or EMTs are developed from averaging the multiple values of the constituents that directly make up the composite material.  At the constituent level, the values of the materials vary and are inhomogeneous.  Precise calculation of the many constituent values is nearly impossible.  However, theories have been developed that can produce acceptable approximations which in turn describe useful parameters and properties of the composite material as a whole.  In this sense, effective medium approximations are descriptions of a medium (composite material) based on the properties and the relative fractions of its components and are derived from calculations. Forged composite is a technology that uses carbon fiber composite material and was developed jointly between Lamborghini and Callaway Golf Company who introduced it in their Sesto Elemento concept car and Diablo Octane drivers, respectively.  The application of this technology was originally developed at the Automobili Lamborghini Advanced Composite Structures Laboratory (ACSL) in Seattle, WA, where the Lamborghini-Callaway partnership was initially formed.  This partnership, along with forged composite technology, was announced at the 2010 Paris Motor Show when Lamborghini unveiled its concept car.  The United States trademark for forged composite was filed on July 13, 2010, in the category Toys and Sporting Goods Products. Stealth aircraft are designed to avoid detection using a variety of technologies that reduce reflection/emission of radar, infrared, visible light, radio-frequency (RF) spectrum, and audio, collectively known as stealth technology.  Development of stealth technology likely began in Germany during World War II, the prototyped Horten Ho 229 was designed for twin BMW 003 jet engines but finally powered by twin Junkers Jumo 004 jet engines being described as the first stealth aircraft.  Well-known modern examples of stealth of U.S. aircraft include the United States' F-117 Nighthawk (1981–2008), the B-2 Spirit, the F-22 Raptor, and the F-35 Lightning II. Composite baseball bats, opposed to aluminum or wood baseball bats, incorporate a reinforced carbon fiber polymer, or composite, into the bat's construction.  This composite material can make up all or part of the bat.  Bats made entirely of this polymer are referred to as composite bats.  Bats which only incorporate a portion of polymer (and the rest either wood or an aluminum alloy) are referred to as composite hybrid bats.  These composite material provides an advantage over aluminum alloys and wood in durability, weight distribution, improved trampoline effect, and a higher damping rate (to reduce hand sting).
Answer: reduce reflection/emission of radar, infrared, visible light, radio-frequency (RF) spectrum, and audio, collectively known as stealth technology.