Composite Materials and Their Place in Aviation

Composite materials are created by combining two or more materials to achieve engineering properties superior to those of conventional materials. By using such materials, together stiffness, strength, lightness, corrosion resistance resistance, thermal properties, fatigue life and wear resistance like can be enhanced in many important feature engineering structures.

Emergence Process

The use of composite materials extends back to the earliest periods of human history. When humans needed more durable materials, they combined basic materials to take the first steps toward composites. For example:

• Mesopotamians in 3400 BCE glued wooden strips at different angles to create plywood.
• Ancient Egyptians produced mud bricks by mixing clay with straw.
• Mongol warriors manufactured composite bows using bamboo, silk, cattle tendons, pine resin and horn. These bows remained in use until the advent of firearms.

Structure

Composite materials are structures composed of at least two components: reinforcement and matrix matrix. The reinforcement material carries the load, while the surrounding matrix phase holds and supports it. Taking the mud brick as an example, straw is the reinforcement phase kil and clay is the matrix phase.

Matrix Phase

In composite materials, the primary functions of the matrix material include maintaining the structural integrity of the reinforcement, facilitating load load transfer, preventing or slowing crack propagation, and protecting the reinforcement from chemical and physical effects. Polymer matrices (thermoset and thermoplastic) are the most common commonly used matrix types, while metal and ceramic matrices are preferred for more specialized applications. The properties of the matrix play a decisive role in the composite structure’s coup strength, delamination, chemical resistance, water absorption and friction resistance during abrasive processes.

Reinforcement Phase

The reinforcement elements used in composite materials are one of the key components of composites and carry a large portion of the applied load. For effective load transfer, a good physical and chemical compatibility and strong interfacial bonding between the reinforcement and matrix are required. Additionally, the matching of thermal expansion coefficients between the reinforcement and matrix is critical to prevent residual stresses in the structure.

Composites in Aviation

Since the Wright Brothers’ first powered flight in 1903, aircraft have evolved from delicate structures made of wire and fabric into high-performance machines constructed from advanced materials. During this transformation transition, composite materials have increasingly replaced steel and aluminum. Although the high safety standards of aviation have made the adoption of composites challenging, their use has progressed from secondary structures (side panels, head overhead bins) to primary structures (wings, body). In addition to their lightness, aviation composites possess many favorable properties:

• Greater lightness
• High impact resistance
• High thermal stability
• Resistance to metal fatigue and corrosion
• Lower material cost
• Radar invisibility (radar stealth)
• Ability to create aerodynamic shapes impossible with wood or metal
• Simplified assembly through reduced part count

The most significant of these properties in aviation is radar invisibility. Certain composites can absorb, redirect or scatter radar waves due to their constituent materials. This situation makes aircraft harder to detect. Important aviation composites and their properties are as follows:

Carbon Fiber Reinforced Polymer (CFRP): Due to its high strength and low weight, this composite ranks first in aviation applications. It is used in fuselages, wings, engine cowlings and landing gear covers.

Glass Fiber Reinforced Polymer (GFRP): The most important application of this composite is in radomes. Radomes allow radar waves to pass through, enabling the acquisition of essential information for flight safety and security. Additionally, they are used in interior panel linings and helicopter blades due to their high impact resistance.

Aramid Fiber Reinforced Polymer (AFRP): What distinguishes this composite is its flexibility. It is used in ballistic protection, helicopter rotor blades and aircraft fuel tanks.

Ceramic Matrix Composites (CMC): This composite stands out for its exceptional resistance to extreme temperatures and can withstand temperatures above 1000°C. Due to this property, it is used in jet engines and thermal protection systems.

Aircraft Using Composite Materials

With the increasing use of composite materials, two aircraft have emerged as the most intensive users in the aviation sector: Boeing 787 and Airbus A350. The greatest advantage of composite materials in aviation is enabling lighter aircraft. This technology trend, which is now widespread, was first introduced in the 1980s during the production of Airbus A320. In the construction of the Airbus A320, 15 percent composite material was used, particularly in the tail section, resulting in a weight savings of 800 grams.

With the growing use of composite materials, the Airbus A380, produced in 2005, became one of the first aircraft to apply this technology on a larger scale. The Airbus A380, the world’s largest passenger aircraft, uses 20 percent composite material. In particular, CFRP (carbon fiber reinforced polymer) used in the “wingbox,” the region where the wings are attached, achieved a weight savings of approximately 1.5 tons.

The Boeing 787, produced in 2008, marked a significant dönüm milestone in the use of composite materials in aviation. More than 50 percent of the aircraft was manufactured from composite materials, ushering in a new generation of aircraft that combined lightness, high efficiency and long range. The Airbus A350, produced in 2013, pushed this further by using more than 53 percent composite materials.

Today, composite materials are widely used in various parts of many aircraft, including interior linings and panels. Given all these developments, it is anticipated that the use of composite materials in the aviation sector will continue to expand and increase further in the future.