Before getting to materials and settings that determine the strength of a part produced using ATL/AFP and composites, it is important to understand the physics and theory behind different aspects that affect its strength. In this section, we cover 3 concepts that lay the groundwork for strong ATL/AFP parts.
Beam Bending Basics
ATL/AFP parts are rarely 100% carbon fiber, as it is beneficial for cost and material savings to reinforce only the sections that experience the most force. This is why most composite parts are constructed more like sandwiches, with the outermost sections being the composite material and the internal structure being the core.
The core's main purpose is to increase the part to the desired thickness, without building it up with expensive carbon fiber. So, does the shell thickness or core density contribute more to part strength? The answer stems from the simple beam bending theory.
The key takeaway from beam bending theory is that the top and bottom surfaces of a beam experience the most force when bent, and we can optimize the strength of a beam for its weight by only adding material at these extremes, and using as little material as possible.
Say we have a simple beam, like a bridge, supported on both sides, and weight is centered between the end supports, as shown in the following diagram.
We can abstract this model to the 3 points of contact the beam experiences - one for the weight, and two for the supports. This forms a triangle, like so, where the contact points become the vertices.