Конструкционные композиты

Отдельно хочется обратить внимание на конструкционные композиты, которые представляют собой широкий класс конструкционных материалов, имеющих полимерную, металлическую или керамическую матрицу. Наиболее типичным примером таких композитов являются углепластики – это композиты с углеволокнами и с полимерной матрицей.

Нанопокрытия

В настоящее время выдающиеся свойства наноматериалов позволяют применять в строительстве новые теплоизоляционные материалы, лаки и многое другое. Большим достижением в области нанопокрытий стала имитация эффекта лепестков лотоса, которые совершенно неуязвимы для воды. В результате в Пекине появилось здание Большого национального театра, огромный яйцеобразный купол которого, созданный из стекла и титана, обработан нанопокрытием, которое не подвержено загрязнению и смачиванию осадками.

По мнению специалистов, внедрение нанотехнологий в строительство в ближайшем будущем создаст настоящий бум по использованию таких наноматериалов как фасадные водонепроницаемые краски. Также одним из актуальных направлений применения наноматериалов является энергосбережение.

Например, полупрозрачные нанопокрытия обладают свойством накапливать солнечную энергию. Данные пленки предназначены для применения их на окнах и стенах зданий: нанопленки придадут фасадам стильный вид, и в тоже время будут работать как солнечные батареи, значительно снижающие расходы на электрическую энергию.

Интересные свойства имеют такие наноматериалы как прозрачные наногели (аэрогели). Они обладают высокими звуко- и теплоизоляционными характеристиками, и в настоящее время их начинают применять в энергосберегающих кровельных системах с верхним светом.

TOPICS FOR DISCUSSION

1. What are the most interesting examples of modern architecture?

2. What are the main advantages and disadvantages of living in a skyscraper?

UNIT 2

Bamboo – the Eco-Friendly Building MateriaL

LEAD-IN

Exercise 1. Give your point of view on the following:

1. Why are eco-materials becoming so popular?

2. What characteristics should eco-materials have?

3. What are the main fields of application of bamboo?

Exercise 2. Read and translate the following words:

Sustainable, spruce, stem, culm, scaffolding, node, bleach, resin, cost-effective.

COMPREHENSIVE READING

Bamboo has become one of the most preferred building materials in recent times. It has garnered attention of serious architects from all across the globe who are employing this hollow-stemmed grass to build all kinds of structures ranging from bridges to luxury homes. Found in almost all continents except for Antarctica and Europe, bamboo is also known as “vegetal steel” due to its environment-friendly appeal. Not only is this plant more lightweight than steel, but it also happens to possess almost five times the strength of concrete.

Bamboo has many advantages as a construction material: it is a rapidly renewable sustainable resource and has mechanical properties similar to timber. Worldwide, there is a growing interest in the development of bamboo products as a sustainable, cost-effective and ecologically responsible alternative construction material. Partially due to the faster growth rate, and therefore harvest cycle, bamboo forests have up to four times the carbon density per hectare of spruce forests over the long term. This consequently allows it to absorb as much as four times of carbon dioxide which is mostly responsible for heating up the planet.

Bamboo is found in rapidly developing areas of the world where often timber resources are limited. While the potential of bamboo is promising, more widespread development and use of bamboo is hampered by the lack of engineering data for mechanical properties and appropriate building codes.

Bamboo is an anisotropic material, having mechanical properties that vary in the longitudinal, radial and transverse directions. The raw material is a giant grass consisting of a hollow culm having longitudinal fibres aligned within a lignin matrix, divided by nodes (solid diaphragms) along the culm length. The thickness of the culm wall tapers from the base of the culm to the top. As a functionally graded material, the bamboo fibres also vary within the culm wall decreasing in density from the exterior to the interior.

While there are more than 1200 species worldwide, full culm bamboo construction is limited by the variation in geometric and mechanical properties. The difficulty in making connections and joints suitable for round (and variable) sections is also prohibitive for mainstream construction; however, increasing research demonstrates a growing industry and demand for sustainable building products. Studies vary from the use of full culm bamboo in construction and scaffolding to engineered bamboo composites. Engineered bamboo composites are of particular interest due to the standardization of shape and the relatively low variability in material properties.

Two examples of engineered bamboo are bamboo scrimber and laminated bamboo. Bamboo scrimber, also referred to as strand woven or parallel strand bamboo, consists of crushed fibre bundles saturated in resin and compressed into a dense block. The process is materially efficient, utilizing approximately 80% of raw inputs, and produces a product with a Janka hardness that is acceptable for external applications such as deck flooring. The process maintains the longitudinal direction of the bamboo fibres and utilizes the resin matrix to connect the fibre bundles. In contrast, laminated bamboo maintains both the longitudinal fibres as well as a portion of the original culm matrix. The bamboo culm is split, planed, processed (bleached or caramelised), laminated and pressed to form the board product. The orientation of the strip within the board, and therefore the direction of the radial fibre density, is randomly placed within in the board. The final products use only approximately 30% of raw material input due to large losses of material when the strips are planed to form the rectangular section. The sheet product is primarily used indoors for surface applications or furniture. While both materials are currently used for surface applications, both maintain the inherent strength of bamboo by maintaining the longitudinal fibre orientation and the engineered product creates a uniform section for connections and joints in structural applications.