Which of the following is NOT a type of material used in product design?

In the context of product design, the focus is on selecting materials that can be used to create functional, safe, and aesthetically pleasing products. Textiles, smart materials, and composite materials are all commonly used in various design applications.

Textiles are used to create soft goods, such as clothing and upholstery, while smart materials, which can change properties in response to external stimuli, have applications in advanced technologies and responsive design. Composite materials, made by combining two or more distinct materials, are utilized for their enhanced strength and lightweight properties, making them ideal for applications in industries like aerospace and automotive.

Hazardous chemicals, while potentially present in some materials, are not considered a type of material used in product design in the same sense as the others listed. Instead, they are substances that pose risks to health and safety, making them unsuitable for direct use in product design with favorable characteristics. Therefore, the inclusion of hazardous chemicals does not align with the intention of modeling materials that are safe and functional for end-use in products, leading to their classification as not being a type of material used in product design.