Early inventions of motor vehicles in the 1920s did not comprise much of polymers as rubber and metal were primarily used for construction. As time progressed, the importance of polymers to the automotive industry was being discovered. Manufacturers realised that polymers had some superior mechanical properties (weight, appearance of polymers, resistance to corrosion, thermal properties, etc.) as compared to metals and would be ideally favourable for motor vehicle applications such as exterior, structural, doors, glazing, interior components, seating, under bonnet, power train, fuel systems and electrics lighting. This is probably the main reason why polymers are being so widely used in automotive industry these days.
However, applying polymers onto vehicles is not as simple as reliability issues need to be taken into consideration. The objective is for manufactures to replace existing materials with polymers, where applicable and at the same time consider the fact that safety must never be jeopardized. Manufactures need to also consider the fact that if they replace any previous component (metal) with polymers there must be guarantee that the component would not fail.
This eventually leads to the major discussion of how the modes of failure (impact and fatigue) of different materials can affect the selection of the type of material used on vehicles. Once the materials in question (metals or polymers) have been identified suitable for vehicles application, it is then possible to compare and recommended which material is suitable for which part. The comparisons will be based on the strength and thermal properties of both the materials. The results through comparisons of quantitative data will aid in determining which parts of the vehicle can be replaced by polymers and which sections will still consist of metals. These comparisons will also determine that some sections are able to utilize, the combination of both metals and polymers on vehicle applications. Therefore vehicles in the future are capable of applying polymer composites (mixture of metals and polymers) for certain applications.