So far manufacturers have relied on three main materials to reduce weight. High-strength steels, which you can use less of; aluminium alloys, which are lighter than steel, and carbonfibre, which is lighter than both of the other two. Now there’s another kid in town called aluminium matrix composite. AMCs are not new but breakthroughs in their development are making them more suitable for automotive applications, especially in EVs.
AMCs are a combination of aluminium alloy mixed with either particles or long or short fibres. The concept is not unlike carbonfibre-reinforced plastic, except the plastic resin is replaced by aluminium. The material can be 50% stiffer and almost 300% stronger than carbonfibre, can withstand severe damage and is stronger than the average steel at half the weight.
It conducts heat well but, crucially, expands very little when it heats up compared with steel or aluminium. That’s important when making precision components. The stiffness of AMC makes it ideal not just for increasing structural integrity but also for reducing noise vibration and harshness (NVH).
Although strong and light, carbonfibre doesn’t withstand abrasion and ballistic impacts well. That’s one reason it isn’t used to make suspension parts on production cars, because it’s so vulnerable to flying grit and stone. Carbonfibre components cannot withstand high temperatures, either, so cars made of it have carefully routed exhaust systems to avoid damage to the structure. Neither is carbonfibre suitable for making internal motor components.
Engineering consultancy Alvant sees huge potential for the use of AMC in EV powertrains and drivelines. It has developed a proprietary manufacturing process called advanced liquid pressure forming (ALPF), which works with any relatively low-melting-point metal such as aluminium alloy.