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Will Composites Muscle In On Plastics In Construction?

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Exel Composites

The building, construction, and infrastructure (BCI) sector uses plastics in many different ways, such as window and door frames, structural support, and piping. Now, the technological and environmental demands of modern buildings are prompting architects and designers to look for new materials.

Here Kim Sjödahl, senior VP of technology and sustainability at global composites manufacturer Exel Composites, explains the developments in composite manufacturing and sustainability that are making fibre-reinforced composites more popular in BCI.

Applications from roofing tiles to exterior cladding and insulation are incorporating composite parts into their designs. As net-zero commitments become more pressing and energy efficiency becomes more important in housing, the material advantages of composites in energy conservation make them significantly more desirable.

According to Eurostat, 80 per cent of the energy used in EU households is for heating, cooling, and hot water. Combined with the fact that 85 per cent of EU buildings were built before 2000 and that 75 per cent of those buildings have a ‘poor’ energy performance, energy waste is a significant issue facing European construction. So, what solutions can composite materials offer?

Material strengths of composites

Composite materials possess several properties that make them suitable for building applications. They are usually more thermally stable materials than most of their plastic counterparts. This is key in windows and doors, one of the primary applications for composites in BCI. Typically, 40 per cent of a building’s heat loss is through its windows and doors, so effective insulation is critical for overall efficiency.

The linear coefficient of thermal expansion of fiberglass composites, 10 × 10−6 °C-1 is much closer to window glass at 6 × 10−6 °C-1, than uPVC, 60 × 10−6 °C-1. This means that fiberglass window frames expand or contract to a similar degree as the glass panes and thus create fewer gaps for air to escape through. Composites are thermally stable over a broad temperature range, -40 up to 80 °C, reducing warping and ensuring a stable structure with an airtight seal.

Composites also have long service lifetimes much greater than 25 years, with examples of up to 100 years of age still performing. Their invulnerability to corrosion, rot, and swelling allows them to retain strength and structural integrity. Additionally, incorporating colour and patterns into the manufacturing process means that paint or other surface treatments being scratched away over time isn’t a concern.

Composites and sustainability

This long service life with small maintenance needs is just one advantage towards sustainable BCI. Fiberglass composite profiles have a typical carbon footprint of 2.8 – 3.5 kg CO2e, which represents the total greenhouse gas (GHG) emissions of a product expressed by the equivalent mass of carbon dioxide.

Only around 20 per cent of the emissions associated with composite material production comes from manufacturing. The remaining 80 per cent actually comes from extraction and refinement of the raw materials used. Exel Composites works proactively with all its suppliers to find solutions to reduce both the upstream 80 per cent and the 20 per cent directly under its control.

Efforts to reduce this 20 per cent under its immediate control include reducing scrap waste and reducing energy used during production, as well as finding the most effective ways of generating the electricity or energy needed. Finally, extensive work is being done to find renewable end-of-life disposal methods and Exel Composites is searching for a composites-to-composites solution for the future.

Manufacturing composites

Pultrusion and pull-winding are two of the foremost continuous composites manufacturing techniques. In the pultrusion process, strands of glass or carbon fibres, mats, and/or technical fabrics are pulled together, saturated with resin, and then pulled into a heated die to cure the resulting thermoset composite. This profile can then be cut to the desired length, machined, and assembled into different constructions. Here, the weight reduction compared to traditional structural materials reduces the transportation carbon footprint and simplifies its use on construction sites.

Pull-winding involves the same steps but some of the fibres are helically wound around a mandrel in the transverse direction before being pulled through the heated die. This allows for greater control over fibre placement and tension, resulting in more uniform and predictable hoop strength.

Both are well suited for high-quality, high-volume production that is cost-effective for customers. These processes enable Exel Composites to provide large composite profiles that have consistent production quality batch-to-batch and are highly repeatable.

While composites are growing in popularity, some architects, builders, and other construction professionals aren’t yet comfortable with using them. One tactic to bridge this gap and add value to customers is to complete the machining on the supply side, producing a complete kit.

In practice, this looks like a labelled and ready-to-assemble collection of all the components needed to put together a window frame, for example. In addition to the composite profiles included, there will also be screws, bolts, and fasteners.

Composite materials are growing in relevance, especially in the building, construction, and infrastructure sectors. Although the relatively short crossover of fibre-reinforced composites with BCI so far means that some in the industry are unfamiliar with working with them up close, developments in manufacturing and mitigating its environmental impact are allowing composite materials’ usage to catch up with their usefulness.

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