Basically, a composite testing is any set of tests that together form the complete test (for example, the conformance test for a CIP node running on EtherNet/IP which includes protocol testing, device description file authentication, physical layer testing, and interoperability testing). An official Composite Test has been adopted and approved by the Conformance Authority for official testing in accordance with the Bylaws and other test development/adoption procedures. This is the final Composite Test.
Why use composites?
There is no doubt that composite materials have a number of advantages, including strength, stiffness, and lightness combined. The use of an appropriate combination of reinforcement and matrix material can lead to the production of properties that exactly match the requirements for a particular structure. This is accomplished by selecting the right combination of reinforcement and matrix materials.
Composite parts have both advantages and disadvantages when compared to the metal parts they are being used to replace.
The advantages of composites
- Fuel savings result from higher performance for a given weight. By using composite materials, you can achieve excellent strength-to-weight and stiffness-to-weight ratios. This is usually expressed in terms of strength divided by density and stiffness (modulus) divided by density. It is these two characteristics that are known as “specific” strength and “specific” modulus that are of interest.
- As a result of the laminate patterns and the ply buildup in a part, it is possible to tailor the mechanical properties in different directions according to what is desired
- Smooth aerodynamic profiles are easier to achieve for reducing drag. It is possible to manufacture double-curved parts with a smooth surface finish in one manufacturing operation even if they have a complex design.
- The number of parts is reduced.
- Costs are reduced during production. A variety of processes can be used to make composites.
- However, some chemicals (e.g., paint stripper) can damage composites, and new types of paint and stripper are being developed to overcome this problem. Composites are excellent at resisting corrosion, chemical attack, and outdoor weathering, but some chemicals can damage them. Some solvents are not very suitable for thermoplastics. Each type’s data sheet should be reviewed
The disadvantages of composites
- It is easier to damage composites than wrought metals because they are more brittle. Brittleness is also a characteristic of cast metals.
- It is necessary to refrigerate materials for transportation and storage, and they have a limited shelf life. Many cases require hot curing, which requires special equipment. Either hot or cold takes time to heal. Installing the last rivet does not complete the job.
- A problem arises when rivets are used and must be removed without causing further damage.
- To repair at the original cure temperature, tooling and pressure are required.
- Before repairing composites, they must be thoroughly cleaned.
- All resin matrices and some fibers absorb moisture, so composites must be dried before they can be repaired.