How can you select materials for use in structural engineering with high levels of UV radiation?

1 UV radiation and its effects

UV radiation is a form of electromagnetic radiation that has a wavelength range of 10 to 400 nanometers (nm). It is divided into three categories: UVA (315 to 400 nm), UVB (280 to 315 nm), and UVC (100 to 280 nm). UVA is the most abundant and penetrates the deepest into materials, while UVC is the most energetic and damaging, but is mostly absorbed by the ozone layer. UV radiation can cause various effects on materials, such as oxidation, photodegradation, cross-linking, chain scission, color fading, cracking, and embrittlement. These effects depend on the type, composition, structure, and exposure time of the material, as well as the intensity and spectrum of the UV radiation.

2 Material selection criteria

When selecting materials for use in structural engineering with high levels of UV radiation, you need to consider several criteria, such as the intended function and design of the structure, the expected service life and maintenance requirements of the material, the cost and availability of the material, the environmental and social impacts of the material, the compatibility and interaction of the material with other materials and components, and compliance with relevant codes and standards. By taking these criteria into account, you can easily narrow down your options and compare the advantages and disadvantages of different materials.

3 Material properties and testing

The next step is to evaluate the properties and performance of the materials under UV radiation. Here, you need to assess both the physical and chemical properties of the materials, such as strength, stiffness, thermal expansion and contraction, moisture absorption and diffusion, corrosion and oxidation resistance, fatigue and fracture resistance, flammability and smoke emission, color stability and aesthetics. Moreover, you should test the materials under simulated or real conditions of UV radiation using methods like accelerated weathering, exposure racks, or field trials. It's important to monitor the changes in the properties and appearance of the materials over time, comparing them with the baseline values and acceptable limits.

4 Material types and examples

Structural engineering in high UV radiation environments requires the use of different materials with varying characteristics, benefits, and drawbacks. Metals such as stainless steel, aluminum, copper, and titanium offer high strength and durability, but can suffer from thermal expansion and contraction, fatigue and fracture, and color fading. Ceramics like concrete, brick, tile, and glass have high compressive strength and fire resistance but are also brittle and prone to cracking. Polymers such as plastics, rubber, and fiber-reinforced plastics are lightweight and flexible yet susceptible to photodegradation, oxidation, cross-linking, and embrittlement. Composites like wood-plastic composites, metal matrix composites, and ceramic matrix composites offer a high strength-to-weight ratio but can face challenges in fabrication, compatibility, and durability. Finally, coatings like paints, varnishes, and sealants can add protection or decoration to underlying materials but may degrade over time. It is important to carefully select each material to ensure that it meets the requirements of the environment while maximizing its potential benefits.

5 Material selection process

The final step is to follow a systematic and rational process for selecting the best material for your project. Utilizing material selection charts, such as Ashby charts, can help compare and rank materials based on criteria and constraints. Additionally, material selection software, like CES EduPack, can aid in filtering and analyzing data of different materials, while material selection case studies, like the Sydney Opera House, can offer insight into successful or failed applications of materials and the best practices. Ultimately, these tools and methods can help you select a material that meets your requirements and expectations, while avoiding the potential risks of using unsuitable materials.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?