Green Guide to Composites: an environmental profiling system for composite materials and products

Anderson, Jane; Jansz, Antonia; Steele, Kristian; Thistlethwaite, Paul; Bishop, Gordon and Black, Adam (2004). Green Guide to Composites: an environmental profiling system for composite materials and products. Watford: BRE Press.



Products made from composite materials can offer significant environmental benefits because of their characteristically low weight, good mechanical properties and excellent resistance to corrosion. For example, composites used in cars can reduce the overall weight of the car and so offer fuel savings through the lifetime of the vehicle. However, although the in-service environmental benefits of composites are known, there is far less understanding of the environmental and social implications associated with the manufacture of composite materials and products.

Issues affecting the industry include health and safety, the emission of volatile organic compounds (VOCs), energy consumption and toxicity from manufacture. Alternative materials and technologies (such as closed mould processes, natural fibres and low-styrene resins) have been developed to address these problems, but to date there has still been confusion within the industry as to the detailed benefits of these alternatives.

This guide has been created to enable the composites sector to understand the environmental and social impacts associated with composite production and assist with the decisions made about material and process choice. The materials and processes modelled are rated from A (good) through to E (poor). Twelve different environmental impacts are individually scored and totalled to give an overall environmental impact summary rating. Two social impact ratings are also given.

When measuring environmental impact it is important to consider all the influences through the life of the product. This process is known as Life Cycle Assessment (LCA) and it has been used in this guide for environmental investigation. Because this guide concentrates on materials and manufacturing, as opposed to in-service performance, the impacts associated with products beyond the factory gate (the use, maintenance and disposal stages of the life cycle) have not been assessed.

Within the system boundaries for the LCA, three typical product types have been chosen to reflect a range of different components commonly manufactured using composites:

• A double curvature panel – this has a surface area of 1m2 with a panel stiffness equivalent to a 4mm thick chopped strand mat laminate.

• A flat sandwich panel – measuring 1m x 8m with a 25mm thick core, having a panel bending stiffness equivalent to a sandwich panel with a 4mm thick chopped strand mat skin.

• A complex moulded component – with a volume of 770cm3.

Similarly, production processes and materials have been selected to provide a balance between systems that are commonly used across the majority of the composites industry and emerging materials with the potential to provide an environmental benefit. For this reason, materials such as hemp fibre and self-reinforced polypropylene have been included in the guide, but materials that are more specific to a single sector (eg aramid fibre) have not been included.

Within each specific process there are still many processing variations (eg methods for mixing, curing and trimming) in addition to the material choice possibilities. To enable fair comparisons, a base case has been selected for each process. This is used throughout the guide to allow the merits of each process variation to be assessed.

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