When a material is struck, dropped, or subjected to other sharp impacts, its impact strength is measured. Impacts, also known as shock loads, can put a lot of strain on materials because they happen so fast. The material doesn’t have time to adapt and distribute the pressure because the incident happens so fast. Impact strength is usually assessed during materials testing, and the manufacturer may provide a rating along with information about the product’s resilience in the face of impacts.
Impact resistance can be a very important trait. Shock loads can happen in an emergency or under less-than-ideal conditions, and material failures could be disastrous. Some materials are kept in low-impact environments until they are required, at which point they may be subjected to enormous forces and must perform consistently. For example, roadside barriers don’t require much stress resistance until a vehicle collides with them, at which point they must absorb and respond to the impact.
Impact strength can be measured using a variety of techniques. In every case, trained technicians use carefully calibrated equipment to achieve a quantifiable and repeatable result. The use of a weighed pendulum is one option. To see what happens, technicians place the material in a cradle and drop the pendulum. They note the amount of impact strain required to begin cracking, bending, or pitting the material, as well as the point at which it fails.
High impact strength can have drawbacks. Because they can deform and bounce back, slightly flexible materials handle impacts better, but this may not be desirable for building materials. Brittle characteristics can be created by making the material tougher and more rigid, which means the material can shatter under relatively low stress. Materials designers must consider a material’s applications and develop the best compromise between available characteristics.
Impact strength testing has some disadvantages. While the equipment is highly controlled and the effects are quantifiable, the controlled conditions can lead to inaccurate material information. Materials may fail at pressures below the expected impact strength in the field, where materials may be mixed, assembled in less-than-ideal positions, weathered, and so on. To achieve the most suitable and applicable results, companies conduct as much testing as possible, including with notched, weathered, and otherwise strained materials.