To fully understand the term composite structure you should know two things: what is composite material and what is structure; because composite structures are simply the structures made by composite materials.
The world of composites is extremely vast and diverse. It is not only about a fancy engine cover on a sports car. We encounter composite structure in our everyday lives: when a bicycle passes us by, when we look up in the air and we spot a plane, and also at home, when we stand on them while taking a shower.
The past few decades have seen outstanding advances in the use of composite materials in structural applications. There can be little doubt that, within engineering circles, composites have revolutionized traditional design concepts and made possible an unparalleled range of new and exciting possibilities as viable materials for construction.
The types of composite structures are so diverse that it is literally impossible to introduce a category that contains all types of composite structures. But the two important types of composite structures that are under research in RRVI are bi-stable composite structures and corrugated composite structures.
What is composite material?
Composite materials (also called composition materials or shortened to composites) are materials made from two or more constituent materials with significantly different physical or chemical properties, that when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure. The new material may be preferred for many reasons: common examples include materials which are stronger, lighter or less expensive when compared to traditional materials.
Typical engineered composite materials include:
- Composite building materials such as cements, concrete
- Reinforced plastics such as fiber-reinforced polymer
- Metal Composites
- Ceramic Composites (composite ceramic and metal matrices)
Composite materials are generally used for buildings, bridges and structures such as boat hulls, swimming pool panels, race car bodies, shower stalls, bathtubs, storage tanks, imitation granite and cultured marble sinks and counter tops. The most advanced examples perform routinely on spacecraft in demanding environments.
Corrugated board
Corrugated board has two main components: the liner and the medium. Linerboard is the flat facing that adheres to the medium. The medium is the wavy plate in between the liners.
A typical corrugated board
Architects have known for thousands of years that an arch with the proper curve is the strongest way to span a given space. The inventors of corrugated board applied this same principle when they put arches in the corrugated medium. These arches are known as corrugation and when anchored to the linerboard with adhesive, they resist bending and pressure from all directions.
Typical types of corrugated boards are:
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Single Face: One medium is glued to one flat sheet of linerboard. |
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Single Wall: The medium is between two sheets of linerboard. Also known as Double Face. |
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Double Wall: Three sheets of linerboard with two mediums in between. |
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Triple Wall: Four sheets of linerboard with three mediums in between |
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The medium alone usually called corrugated plate. These plates might be classified based on the shape of their core. Trapezoidal and sinusoidal corrugated profiles are among the most common profiles used in industry. These plates show higher stiffness-to-mass ratio in the transverse to corrugation direction in compare to flat plates. Because of these advantages, corrugated plates have been used in various engineering applications, such as shipbuilding, roofing, packaging and recently in the aerospace and aeronautics engineering.
A corrugated sheet with trapezoidal corrugation
One of the recent applications of these structures is the morphing wing. Current standard of adaptive airfoil geometry is deployable flaps which cause limitation on maneuverability and is non-optimal in many flight regimes. Such a need has been developed for a wing whose contour can be changed due to the flight conditions. Due to the extremely anisotropic behavior of corrugated panels, these structures have been proposed as a candidate for the skin of morphing wing. These panels are flexible in the corrugation direction which allows the shape changes and they are stiff in the transverse to the corrugation direction which enables them to withstand the aerodynamic and inertial loads.
Corrugated composite as flexible morphing wing structure.