CFRTP can be molded by pressing an intermediate material called prepreg.
There are two types of prepreg: prepreg with fibers oriented in two directions (plain weave or twill weave) and prepreg with fibers oriented in only one direction (UD).
The fiber orientation of prepreg with plain weave or twill weave is half that of one-directional prepreg, so the strength is also about half.
plain weave prepreg uni-directional prepreg
Then, what kind of fracture will occur when the prepreg actually becomes a molded product?
This time, we experimentally created a molded product using a combination of three types of prepreg, performed a three-point bending test, and confirmed the fracture with a camera.
We then conducted a 3-point bending test and confirmed the fracture with a camera.
First, a laminated product made of plain weave prepreg (6ply)
Failure was observed to begin in the area in contact with the pressure element (lower side).
The three-point bending test is performed by applying compressive and tensile loads to the test piece.
Carbon fiber has very strong physical properties under tensile loads, but is weak under compressive loads.
However, it is weak under compressive load, and it is thought that the potential of CarbonFiber cannot be fully demonstrated. It is thought that the potential of carbon fiber cannot be fully demonstrated.
Then, how does it behave when UD prepreg is laminated on the tensile side?
(Plain weave: 3ply UD: 3ply)
Fracture appears to start in balance between the compression and tensile sides. when UD is used on the tensile side.
I think it can be said that the strength of carbon fiber can be fully demonstrated if UD is used on the tensile side.
Now, what will happen if UD prepreg is laminated on the compression side?
(UD: 3ply, Plain weave: 3ply)
Failure started on the compression side, but it was the plain weave prepreg on the tension side that determined failure. We found that the failure modes were completely different.
By changing the stacking pattern of CFRP, not only the strength but also the fracture mode can be changed.
We must continue to conduct such experiments to find the best lamination method for each specification.
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