A while ago, I wrote a simple document for undergraduates in order to explain that composite materials can fail in different ways. This was created as a high level document which could be used to find useful references with regards to failure modes, basic failure criteria and damage propagation models. I wanted to share this with you in case you are new in this field or just if you simply want to learn some basics of composites!
A composite can be defined as a material which is composed of two or more constituents of different chemical properties, with resultant properties different to those of the individual components. They usually consist of a continuous phase (matrix) and a distributed phase (reinforcement). These reinforcements can be fibrous, particulate or lamellar and they are usually stiff and strong, so that they are responsible for providing the stiffness and the strength of the composite. On the other hand, the matrix provides shear strength, toughness and resistance to the environment.
Fibre reinforced composites are considered as the strongest and sometimes also the stiffest, due to:
- Alignment of molecules or structural elements.
- Very fine structures.
- Elimination of defects.
- Unique structures.
- Statistical factors.
With regards to fibre reinforced composite materials, their main failure modes are:
- Fibre failure induced by tension in fibre direction.
- Fibre failure induced by compression in fibre direction.
- Matrix fracture induced by tension.
- Matrix fracture induced by compression.
It is remarkable that fibre failure typically caused composite failure, whereas matrix failure may not cause the same drastic effect. Continue reading