JPH01201385A - Method of bonding fiber-reinforced plastic - Google Patents

Abstract

PURPOSE:To firmly bond either the surfaces of fiber-reinforced plastics to each other or the surface of a fiber-reinforced plastic to the surface of other material, by preliminarily applying a laser beam to the bonding surface when a molded material of a fiber-reinforced plastic is bonded by means of an adhesive. CONSTITUTION:In bonding a molded material of a fiber-reinforced plastic by means of an adhesive, a laser beam is preliminarily applied to the bonding surface to evaporate a base plastic and expose the reinforcing fiber on the surface, thereby forming microscopic unevennesses while maintaining macroscopic smoothness. Since a number of reinforcing fibers are exposed on the bonding surface of the molded material of a fiber-reinforced plastic, an improvement in the adhesive power can be attained by an anchor effect between the reinforcing fiber and the adhesive layer, an increase in the bonding area derived from the exposed surface of the reinforcing fiber, entanglement between reinforcing fibers exposed on both the bonding surfaces, etc. besides adhesive power between the surface of an adherend and an adhesive layer produced during conventional adhesion and deformation restraint due to shrinkage of the adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improved method for firmly bonding fiber-reinforced plastics with an adhesive.

Conventional technology Fiber-reinforced plastics, especially plastics reinforced with inorganic fibers such as glass fibers, carbon fibers, and metal fibers, have superior heat resistance and mechanical strength compared to the plastics they are made from, so they are used in plates, tubes, and rods. It is widely used as a molding material for machine parts, etc.

By the way, when secondary processing this fiber-reinforced plastic molded product into mechanical parts, various appliances, laminates, etc., bonding with an adhesive is often required. Generally, the joint surfaces are finished smooth and cleaned.

However, when bonding is performed in such a state, there are no fibers between the surface of the bonded object and the adhesive layer, even though the bonded object is reinforced with fibers throughout, and the adhesive layer is simply Since it is bonded only by the bonding force with the surface of the object to be adhered and the deformation restraint force generated by the shrinkage of the adhesive layer, its strength is inevitably considerably lower than that of the object to be adhered.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of such conventional bonding methods for fiber-reinforced plastics, and provides a method for firmly bonding fiber-reinforced plastic surfaces to each other or to the surface of another object. This was done with the purpose of providing an improved method for.

Means for Solving the Problems The present inventors have conducted various studies on bonding methods for fiber-reinforced plastics, and have found that when fiber-reinforced plastics are irradiated with a laser, laser energy is transferred between the base plastic and the reinforcing fibers. Because of the difference in absorption rate, the former will preferentially evaporate, leaving the latter exposed. Therefore, if an adhesive layer is placed on top of this, the exposed evaporation will occur between the surface of the adherend and the adhesive layer. It was discovered that the reinforcing fibers produce an anchor effect, and the present invention was developed based on this finding.

That is, the present invention provides a method for bonding fiber-reinforced plastics, which is characterized in that, when bonding fiber-reinforced plastic molded bodies using an adhesive, the bonded surfaces are subjected to laser irradiation treatment in advance.

In the method of the present invention, the fiber-reinforced plastic molded bodies to be adhered are those based on thermosetting resin, so-called FRP, and those based on thermoplastic resin, so-called FRP.
Either RPT may be used.

Examples of the thermosetting resin base material include epoxy resin, unsaturated polyester resin, phenol resin, urea resin, melamine resin, and alkyd resin, and examples of the thermoplastic resin base material include polyamide, polycarbonate, polyacetal, Examples include ABS resin, AS resin, polypropylene, high density polyethylene, and polyester.

Next, as reinforcing fibers to be contained in this base material, for example, inorganic fibers such as glass fibers, carbon fibers, metal fibers, and ceramic fibers, and organic fibers such as aramid fibers and polyoxymethylene whiskers can be used. I can do it, but
It is preferable to use inorganic fibers because exposure can be easily carried out based on the difference in absorption rate of laser energy. These reinforcing fibers are long fibers, short fibers, twisted fibers,
It can be composited with a base material in any shape such as curled thread, knitted fabric, or woven fabric.

The object to be adhered in the method of the present invention is not limited to the content of reinforcing fibers in these fiber-reinforced plastics or the types of additives contained in the base material, and any of the fiber-reinforced plastics commonly used up to now can be used. It can also be applied to

Further, there is no particular restriction on the shape of this fiber-reinforced plastic molded article, and it may be of any shape, such as a plate, a tube, a rond, or an irregular shape, as long as the bonding surface can be made smooth.

On the other hand, there are no particular restrictions on the adhesive for bonding this fiber-reinforced plastic molded product, and any adhesive that has been used for fiber-reinforced plastic molded products can be used as is. Examples of such adhesives include:
Epoxy adhesives, polyester adhesives, acrylic adhesives, urethane adhesives, resorcinol adhesives,
Examples include synthetic rubber adhesives.

In order to adhere fiber-reinforced plastic molded bodies according to the method of the present invention, first, the bonding surfaces of the molded bodies are polished and smoothed by a conventional method, and further, if necessary, a cleaning treatment with a chemical solution is performed.

Next, laser irradiation treatment is applied to the joint surface treated in this way to evaporate the base plastic and expose the reinforcing fibers on the surface, forming microscopic irregularities while maintaining macroscopic smoothness. let

At this time, it is necessary to control the amount of laser irradiation so that only the base plastic can be efficiently evaporated without damaging the reinforcing fibers themselves.

For example, when glass fibers are used as the reinforcing fibers, if the irradiation dose is too high, a portion of the glass fibers will melt and evaporate to form brittle SiC, which will actually reduce the adhesive strength.

The appropriate amount of laser irradiation varies depending on the type of base plastic, the type of reinforcing fiber, etc., but is usually in the range of 0.0004 to 0.017 Wmin/m as an average heat input. However, average heat input - (laser output) / (emission width) x (laser movement distance per minute) After performing laser irradiation treatment in this way, apply the specified adhesive to the surface to be bonded. ,
Bonding is performed using this adhesive layer in accordance with a conventional method. The thickness of the adhesive layer at this time is suitably in the range of 0.05 to 0.5 mm.

The method of the present invention is particularly effective when bonding fiber-reinforced plastic molded bodies together, and can also be used to bond fiber-reinforced plastic molded bodies to other objects.

In the method of the present invention, it is possible to obtain a sufficiently strong bond by simply bringing the joint surfaces of each adherend into contact and holding them through the adhesive layer, but by applying pressure during bonding,
Furthermore, adhesive strength can be increased. In addition, the adhesive strength can be improved by combining treatments that are normally performed to increase the affinity between reinforcing fibers and adhesives, such as the 7-run treatment that is performed when glass fibers are used as reinforcing fibers. can be increased.

Function In the present invention, since a large number of reinforcing fibers are exposed on the bonding surface of the fiber-reinforced plastic molded article, the adhesive force between the surface of the adherend and the adhesive layer that occurs during conventional bonding is reduced. In addition to the deformation restraining force due to the contraction of the adhesive layer, there is also an anchor effect between the reinforcing fibers and the adhesive layer, an increase in the bonding area based on the exposed surface of the reinforcing fibers, and entanglement of the reinforcing fibers exposed on both bonding surfaces. Improved adhesion strength can be achieved.

Example Next, the present invention will be explained in more detail with reference to Examples.

The laser irradiation at each point was performed using a CO2 laser oscillator [EL tool manufactured by Daihen Co., Ltd., focusing lens (2 nSc), focal length 5 inches], the flow rate of Ar as assist gas was 50 Q/min, and the laser output was 200 W.

Processing speed 5m/min, distance from focal point to processing surface 115m
The test was carried out under conditions of 0.6×10 −2 W-min/mm 2 and an average heat input of 0.6×10 −2 W-min/mm 2 .

Example 1 Two glass fiber reinforced epoxy resin rods (150x2
The minimum area surface of 2×20I+Im) was polished, and further degreased and washed with acetone to form a bonding surface.

Next, the laser beam is irradiated over the entire surface of the bonded surface while moving the laser center in 5 mm increments, and then 0.3 epoxy resin adhesive is applied to the bonded surface of one of the rods.
Apply it to a thickness of mm, make each joint surface adhere, and apply Teflon
Fix with 0 log glass adhesive tape and 1 at lOO'C.
Allowed to cure for hours.

For the samples thus obtained, the tensile speed was 0,5
When a tensile test was carried out at 7 minutes, the maximum tensile stress was 0.48 kg/mm2.

For comparison, a tensile test was conducted on a sample bonded in the same way using a bar without laser irradiation treatment, and the maximum tensile stress was 0 and 20 kg/m.
It was m2.

Example 2 Glass fiber reinforced epoxy resin plate (+50X 100
After laser irradiation was performed on the minimum area surface of 20 x 100 x 20 sheets in the same manner as in Example 1, a thick layer of Stycast+266 (poxy resin adhesive manufactured by Emerson & Kasing) was applied to one of the treated surfaces. It was applied to a thickness of 0.3 mm, and the two bonded surfaces were brought into close contact. Next, use a pressure jig to reduce the pressure perpendicular to the joint surface to 0,01179
1/mm" or 0.1 kgI/mrn2 was added and held for 48 hours to cure. When a tensile test was conducted on the sample thus obtained, the pressure was 0.0, 0.1 kgI/mrn2.
The maximum tensile stress of kgI/mm2 is 3,
26 kg/mm2, 0,1 kgf/m
The maximum tensile stress after adding m2 is 3,32 kg/
It was mm2.

In addition, for comparison, a tensile test was performed on samples bonded in the same manner without laser irradiation, and the corresponding maximum tensile stresses were 0 and 95 kg, respectively.
/ mm2.0, 98 kg/IIIys”.

Example 3 Carbon fiber-reinforced epoxy resin was used instead of glass fiber-reinforced epoxy resin, and the processing speed during laser irradiation was set to 2.
Adhesion was carried out in the same manner as in Example 1, except for changing the bonding speed to m/min. When the tensile test of the sample thus obtained was conducted, the maximum tensile stress was 0.123 kg/mm''.

For comparison, we performed a tensile test on a sample of the same carbon fiber-reinforced epoxy resin that was bonded in the same way without laser irradiation, but the bonded part broke when it was installed, making it impossible to measure. There wasn't.

Example 4 Between two plates (50 x 22 x 20 mm) made of the same glass fiber reinforced epoxy resin as used in Example 1, two plates (IsOX 30 x 20 a) made of the same material were placed.
m) was sandwiched, and each joint surface was adhered in the same manner as in Example 1.

For the samples obtained in this way, the tensile speeds were 0 and 5.
The longitudinal shear strength was measured in rrutr/min.

As a result, the maximum shear strength when laser irradiation was applied to all of the joint surfaces was 0.480 kg/mm'', and the maximum shear strength when no laser irradiation was performed was 0.122 kg/mm''.

Effects of the Invention According to the method of the present invention, when bonding fiber-reinforced plastics using an adhesive, the adhesive strength can be increased by more than double by simply irradiating the bonding surface with a laser in advance.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. A method for adhering fiber-reinforced plastics, which comprises subjecting the bonded surfaces to laser irradiation treatment in advance when bonding fiber-reinforced plastic molded objects using an adhesive.