Common adjectives for carbon fiber products:
High strength = Not easily torn apart
High modulus = Not easily stretched or shortened
But there's another characteristic of carbon fiber products:
Low impact strength ≈ Either no deformation occurs, or it breaks
To understand this concept, one must first realize that carbon fiber products are made by layering sheets of carbon fiber fabric, which are then bonded together with resin to form the final product.
In the field of composite materials, besides the "either unchanged or broken" scenario, there's another possibility: delamination of the reinforced fiber layers.
Terminology: When a carbon fiber composite material structure is subjected to an out-of-plane impact, delamination can occur between the layers due to matrix damage, leading to instability when subjected to compressive stress.
Layman's terms: Upon impact, the carbon fiber itself remains intact, but the glue holding the different layers together fails, causing delamination.
This type of damage is known as barely visible impact damage (BVID). To detect BVID, CT scanning is the only reliable method.
