JPH04340437A - Lamination-configuration method of cfrp interlayer breakdown toughness test piece - Google Patents

Abstract

PURPOSE:To produce a carbon fiber composite material test piece which is not twisted even if delamination is performed by setting a portion to be subjected to delamination to asymmetrical lamination angles in upper and lower directions, a lamination angle to be symmetrical at both upper-side and lower- side lamination portions, and by setting those fiber angles to be equal. CONSTITUTION:When a test piece is produced by laminating a material 1 so that directions of a carbon fiber 2 differ, lamination portions A and B are in symmetrical lamination each other to prevent an upper-side lamination portion A and a lower-side lamination portion B which are released at the time of test from being warped and twisted. Namely, the interlayer to be released as an entire test piece is in an asymmetrical layer with a fiber angle of thetadegrees and that of -theta degrees crossing it. However, the upper-side lamination portion A which causes the delamination is in symmetrical layer as in theta -theta, -thetaand theta, the lower-side lamination portion B is in a symmetrical layer as in -theta, theta, theta, and -theta, and further the lamination angle theta and -theta are set to the same angle at the lamination portions A and B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of laminating a test piece used in a test for determining the fracture toughness between layers of CFRP having different lamination angles.

0002

2. Description of the Related Art Among FRP (fiber reinforced composite materials), CFRP (carbon fiber composite material) is a typical example used in aircraft, and is used for radomes, floors, doors, etc.

[0003] The above-mentioned CFRP is made by laminating carbon fibers in multiple layers, with the fibers oriented in different directions in each layer. In other words, when manufacturing CFRP plates,
As shown in FIG. 4, the material 1 containing carbon fibers 2 is laminated in multiple layers and bonded between the layers, and at this time, the direction of the fibers 2 is set at an angle of θ degrees in a certain layer. In this case, in the next layer, the direction of fiber 2 is in the direction crossing this -
They are stacked so that the angle of fiber 2 is θ degrees.
The material 1 is laminated so that the degree and -θ degree are alternately repeated, and the materials 1 are bonded to each other to manufacture a lightweight and durable CFRP plate.

In the case of CFRP made of laminated materials 1 containing carbon fibers 2 as described above, when an impact is applied from the direction of arrow a as shown in FIG. It has been confirmed through experiments that cracks b are occurring, and if cracks b occur, there is a risk of peeling between the laminated corners.

[0005] The above-mentioned state of interlayer peeling cannot be confirmed from the outside, nor can the adhesion between the layers be confirmed. Therefore, it is necessary to determine the strength (interlaminar fracture toughness) between layers having different fiber angles, that is, between lamination angles.

[0006] In order to determine the above-mentioned interlaminar fracture toughness, an interlaminar fracture toughness test is carried out. A shearing force is applied to the material to cause it to peel off, and test specimens are prepared in advance and interlaminar fracture toughness tests are carried out.

[0007]

[Problem to be Solved by the Invention] However, when delamination is performed between the lamination angles when the layers are laminated so that the angles are alternately θ and -θ as shown in FIG. Therefore, it has been well known as common knowledge that when the layers are separated, the upper and lower layers warp and twist. Therefore, when making a test piece, the direction of the fibers of the laminated materials is all the same (0 degrees) so that the layers are symmetrical, and during the delamination toughness test,
Although this is done to prevent twisting, since CFRP is made by alternating the directions of the fibers in θ and -θ so that the angles between the layers are different, the test specimens shown above do not match the actual lamination of CFRP. There is a problem in that this does not mean that the interlaminar fracture toughness between the corners has been tested. In order to eliminate this problem, when making a test piece, if the layers are stacked so that the angles θ and -θ are repeated for each layer as shown in FIG. Therefore, the test piece is twisted when it is peeled off, making it impossible to measure the fracture toughness in a pure mode.

[0008] In this way, when determining the interlaminar fracture toughness between different types of laminations, if a simple lamination construction method is used, the test piece will be twisted due to the strong anisotropy of CFRP, making it impossible to measure the fracture toughness.

[0009] Accordingly, the present invention aims to provide a method of laminate construction that can produce a test piece that will not twist in an interlaminar fracture toughness test even if the laminate is asymmetrically stacked vertically.

0010

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides that the layers to be peeled are stacked asymmetrically on the top and bottom, and that both the upper and lower layers that cause delamination are The lamination method is such that the laminations are symmetrical and the fibers are oriented at the same angle in each lamination.

[0011]

[Operation] Even if there is an asymmetrical lamination between the upper and lower layers to be peeled, since the lamination angles of both the upper laminated part and the lower laminated part are symmetrical, there will be no twisting during delamination. , it becomes possible to determine the interlaminar fracture toughness between asymmetric lamination angles.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the laminated structure of the present invention.
As shown in Fig. 4, when making a test piece by laminating the material 1 so that the directions of the carbon fibers 2 are different between the layers, the interlayers where delamination occurs are different, such as θ degrees and -θ degrees. In order to prevent the upper laminated part A and the lower laminated part B of the test piece, which peel off during the interlaminar fracture toughness test, from warping and twisting even at the lamination angle, the upper laminated Part A and the lower laminated part B are each symmetrically laminated. That is, as for the test piece as a whole, the interlayers that cause delamination are asymmetric laminations with a fiber angle of θ degrees and a fiber angle of -θ degrees in the direction crossing this, but the upper laminated part A that causes delamination are laminated symmetrically such as θ, -θ, -θ, θ, and the lower laminated part B is laminated symmetrically such as -θ, θ, θ, -θ, and furthermore, the lamination angle θ and - θ is set to be the same angle in the upper laminated portion A and the lower laminated portion B, for example, 45 degrees or 30 degrees.

[0014] With the laminated structure example as described above, even if the lamination angles are asymmetric in the interlaminar fracture toughness test, the upper laminated part A and the lower laminated part B are symmetrical laminated, so the test can be performed. It was confirmed that the pieces were not twisted. In this case, the stacking angle θ between the upper stacked part A and the lower stacked part B is -
When the angles of θ are different, for example, the laminated angles θ and -θ of the upper laminated part A are both 45 degrees, and the laminated angles θ and -θ of the lower laminated part B are set to 45 degrees.
It has also been confirmed that when the lamination angles θ and −θ are both 30 degrees, the upper and lower lamination parts A and B are twisted due to the difference in coefficient of thermal expansion.

As an example of an interlaminar fracture toughness test conducted using a test piece I laminated by the laminated structure method of the present invention, an artificial defect 3 is formed between the layers to be peeled off as shown in FIG. By applying a tensile force P in the vertical direction and peeling the three parts vertically, we will examine how the parts peel off and the resistance of the material when peeling. The above-mentioned artificial defect 3 is formed by stacking the test pieces I with the film 4 sandwiched between them, and then removing the film 4 to form a state in which cracks have already appeared. In addition, as another example of the interlaminar fracture toughness test, as shown in FIG.
is placed on two supports 5, and a pressure P0 is applied from above at the intermediate position to bend the test piece I at three points, causing delamination due to shearing from the artificial defect 3. .

[0016]

[Effects of the Invention] As described above, according to the lamination structure method of the CFRP interlaminar fracture toughness test piece of the present invention, the layer to be peeled is asymmetrical lamination, but the upper laminated portion causing delamination is asymmetrical. The lower laminated parts are all symmetrical laminated,
Furthermore, since the upper and lower laminated parts are laminated with the same fiber angle, even if delamination occurs during an interlaminar fracture toughness test between different laminated layers, the test piece will not warp or twist. This has the excellent effect of being able to determine the fracture toughness between different lamination angles even with a simple test method.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a laminated structure for making a CFRP interlaminar fracture toughness test piece of the present invention.

FIG. 2 is a schematic diagram showing an example of an interlaminar fracture toughness test.

FIG. 3 is a schematic diagram showing another example of an interlaminar fracture toughness test.

FIG. 4 is a perspective view showing the procedure for laminating CFRP.

FIG. 5 is a cross-sectional view showing a state in which cracks occur between layers due to impact.

FIG. 6 is a schematic diagram showing a case where a test piece is made according to the lamination procedure shown in the figure.

[Explanation of symbols]

1 Material 2 Carbon fiber 3. Artificial defects I Test piece θ, −θ angle A Upper laminated part B Lower laminated part

Claims (1)

[Claims] Claim 1: An asymmetric laminated layer in which the angles of fibers are asymmetrical between the upper and lower layers that separate when performing an interlaminar fracture toughness test, and an upper laminated portion and a lower laminated portion that cause peeling between the upper and lower asymmetric laminated layers. A laminate construction method for a CFRP interlaminar fracture toughness test piece, characterized by forming symmetrical laminations with symmetrical fiber angles, and further making the fiber angles of the upper laminated part and the lower laminated part the same. .