JP6547784B2 - Interface strength evaluation method for fiber reinforced composite materials - Google Patents

Description

  The present invention relates to a method for evaluating the interfacial strength of a fiber-reinforced composite material.

  Conventionally, the nanoindentation method (hereinafter referred to as the NI method) is known as one of methods for evaluating mechanical properties such as hardness and elastic modulus of minute portions of materials (for example, see Patent Document 1). .

  In particular, in the case of a molded product or the like containing a fibrous additive, it is important to evaluate the interface strength or the like between the additive and the base material in order to evaluate the strength or the like of the molded product. From such a point of view, an NI method capable of evaluating the mechanical characteristics of minute parts is expected.

  In the NI method, the mechanical properties of a minute part are evaluated by pressing a diamond indenter into a sample and measuring the pressing strength (load) and pressing depth (displacement) of the sample.

Unexamined-Japanese-Patent No. 2004-257775

  By the way, conventionally, for the purpose of evaluating the physical properties of minute parts of a molded product, when preparing a sample for the NI method, for example, a thin film sample is cut out by a microtome method or the like.

  However, the sample cut out by the microtome method or the like has a possibility that the internal structure of the sample may change due to the stress applied to the sample during the cutting operation. Moreover, the surface roughness of the sample after being cut out is large, and there is room for improvement from the viewpoint of improving the measurement accuracy.

  Therefore, an object of the present invention is to provide a measurement method capable of improving measurement accuracy when measuring the interfacial strength of a fiber-reinforced composite material using the NI method.

  In order to achieve the above object, according to the present invention, when producing an evaluation sample used for NI measurement, both surfaces of the sample are polished and the surface roughness Ra of the measurement surface to which the indenter is pressed is within a predetermined range. It was polished to become.

That is, in the method for evaluating the interfacial strength of a fiber-reinforced composite material according to the first technique disclosed herein, the matrix of the fiber-reinforced composite material in which fibrous particles are dispersed in the matrix and the fibrous particles A method of evaluating interfacial strength of a fiber-reinforced composite material, the interfacial strength being evaluated using a nanoindentation method, comprising: cutting out a plate-like sample from a molded article of the fiber-reinforced composite material; And a polishing process for polishing to obtain a sample for evaluation, wherein in the polishing process, the measurement surface on the side to which the indenter in the nano-indentation method is pressed in of the two polished surfaces of the sample for evaluation is a predetermined one. The surface of the sample is polished until the surface roughness Ra is reached, and in the polishing step, the back surface of the sample is polished to form the back surface of the sample for evaluation, and then the surface of the sample is polished Polishing of measurement surface And performing.

  As described above, when the evaluation sample is cut out using a conventional microtome etc., there is a possibility that unnecessary stress may be applied to the evaluation sample, and the surface roughness Ra of the evaluation sample is large and it is difficult to measure with high accuracy. Become.

According to the first technique, the sample is cut out from the molded product, and the measurement surface side to which the indenter is pressed is polished until the predetermined surface roughness Ra is achieved, so that the surface roughness Ra suitable for measurement by the NI method is thin. A sample for evaluation can be obtained, and measurement accuracy by the NI method can be improved. In addition, by polishing the back surface of the sample first and then polishing the surface of the sample, the possibility of contamination of the measurement surface of the sample for evaluation can be reduced.

  A second technique according to the first technique is that the surface roughness Ra of the measurement surface of the evaluation sample is 0.05 μm or more and 1.5 μm or less.

  According to the second technique, it is possible to effectively improve the measurement accuracy by the NI method by polishing so that the surface roughness Ra of the measurement surface of the evaluation sample is in the above range.

  According to a third technique, in the second technique, among the polished surfaces of the evaluation sample in the polishing step, the surface roughness Ra of the measurement backside opposite to the measurement surface is also 0.05 μm or more It is polished to 1.5 μm or less.

  Since the evaluation sample used for measurement of the NI method is a thin sample having a thickness of less than 1000 μm, not only the measurement surface on which the indenter is pressed in, but also the surface roughness of the back surface of the evaluation sample affects the measurement accuracy. It can be exerted. According to the third technique, it is possible to effectively improve the measurement accuracy by the NI method by polishing the back surface of the sample until the surface roughness Ra falls within the above range.

A fourth technique according to any one of the first to third techniques is that the thickness of the evaluation sample is 0.5% or more and 7% or less of that of the sample.

According to the fourth technique, by polishing the sample to a thickness in the above range, it is possible to obtain a sample for evaluation that has not been damaged by the cutting process.

According to a fifth technology, in the fourth technology, the thickness of the sample cut out in the cutting step is 3 mm or more and 10 mm or less, and the thickness of the evaluation sample obtained in the polishing step is 50 μm or more and 200 μm or less.

According to the fifth technique, it is possible to obtain a thin sample suitable for measurement by the NI method, and a sufficiently small sample for evaluation of surface roughness.

According to a sixth technology, in any one of the first to fifth technologies, an embedding process for embedding the sample in a resin after the cutting process and before the polishing process, and in the resin And a mounting step of fixing the embedded sample to a polishing holder using a bonding material, and in the polishing step, the sample embedded in the resin and fixed to the polishing holder is polished.

According to the sixth technique, by embedding the sample cut out in the cutting step in the resin, it is possible to prevent damage to the polishing surface or the like due to polishing debris or the like generated during polishing. Further, by fixing the sample to the polishing holder, a small sample can be stably held during the polishing process, and the polishing operation becomes easy.

A seventh technique according to the sixth technique further comprises a removal step of removing the evaluation sample from the polishing holder after the polishing step, and in the removal step, the evaluation sample is a sample for evaluation The polishing holder is removed from the polishing holder by heating and melting a bonding material disposed between the two.

According to the seventh technique, by melting the bonding material, it is possible to easily remove the sample from the polishing holder, and it is possible to suppress damage to the polishing surface of the sample associated with the removal operation.

The eighth technique is a fiber-reinforced composite material for evaluating the interfacial strength between the matrix and the fibrous particles of the fiber-reinforced composite material in which fibrous particles are dispersed in the matrix using a nano-indentation method. A method for evaluating interfacial strength, comprising: a cutting step of cutting out a plate-like sample from a molded article of the fiber reinforced composite material; and a polishing step of polishing both surfaces of the sample to obtain a sample for evaluation Of the polished surfaces of the evaluation sample, the measurement surface on the side where the indenter is pressed in the nanoindentation method is polished to a predetermined surface roughness Ra, and after the cutting step And before the polishing step, the method further includes an embedding step of embedding the sample in a resin, and an attaching step of fixing the sample embedded in the resin to a polishing holder using a bonding material, the polishing Process, the resin And the removal step of removing the sample for evaluation from the polishing holder after the polishing step, wherein the sample for evaluation is removed in the removal step. The bonding material disposed between the evaluation sample and the polishing holder is removed from the polishing holder by heating and melting, and the bonding material is paraffin.

  The melting point of paraffin is relatively low, about 60 ° C. Therefore, according to the eighth technique, it is possible to remove the sample from the polishing holder at a relatively low temperature. Thus, damage to the sample that may occur as the sample is desorbed to the polishing holder can be suppressed.

In a ninth technique according to any one of the first to eighth techniques, at least the measurement surface of the polished both surfaces of the evaluation sample in the polishing step is rotated at a rotational speed of 120 rpm by a rotary polisher. It is formed by polishing with a buffing cloth with alumina at a rotational speed of 80 rpm or more and less than 120 rpm after being polished by sand paper at 140 rpm or less.

According to the ninth technique, after rough polishing is performed by sand paper polishing, final polishing using a buff cloth with alumina can be performed to obtain a measurement surface having a small surface roughness Ra. In addition, as the thickness of the sample decreases, the rotation speed of the rotary polishing machine can be reduced to prevent damage or cracking of the sample during polishing. In addition to the measurement surface, polishing of the back surface of the measurement may be performed using the above conditions.

The tenth technique is a fiber-reinforced composite material for evaluating the interfacial strength between the matrix of the fiber-reinforced composite material in which fibrous particles are dispersed in the matrix and the fibrous particles using a nano-indentation method. A method for evaluating interfacial strength, comprising: a cutting step of cutting out a plate-like sample from a molded article of the fiber reinforced composite material; and a polishing step of polishing both surfaces of the sample to obtain a sample for evaluation Of the polished surfaces of the evaluation sample, the measurement surface on the side where the indenter is pressed in the nanoindentation method is polished to a predetermined surface roughness Ra, and after the polishing step, An arranging step of arranging the evaluation sample in a measurement holder, and an evaluation step of evaluating interface strength of the fiber reinforced composite material by pressing the indenter into the measurement surface of the evaluation sample arranged in the measurement holder Prepare , The mounting portion, wherein the evaluation sample of the measuring holder is mounted so as to evaluate the surface strength of the plurality of positions of the evaluation sample, the plurality of measurement hole.

In the measurement of the NI method, the measurement point of the evaluation sample is displaced in the pressing direction by the pressing of the indenter. Therefore, in the measurement holder on which the evaluation sample is placed, measurement holes are formed at positions corresponding to the measurement points so as not to prevent the displacement of the evaluation sample. According to the tenth technique, the interface strength of the composite material is measured at a plurality of measurement points in one evaluation sample by placing one evaluation sample so as to cover a plurality of measurement holes. Can. Then, for example, it becomes possible to evaluate the difference in interface strength between the vicinity of the central portion and the vicinity of the outer edge portion in one evaluation sample.

  As described above, according to the present invention, a thin evaluation sample having a surface roughness Ra suitable for measurement by the NI method can be obtained, and measurement accuracy by the NI method can be improved.

FIG. 1 is a perspective view of TP. FIG. 2 is a flowchart for explaining the preparation procedure of TP. FIG. 3 is a perspective view schematically showing a state in which a sample is cut out of an automobile part in the cutting step of FIG. FIG. 4 is a perspective view of the sample cut out in the cutting step of FIG. FIG. 5: is a perspective view which shows typically the mode of the attachment process in FIG. FIG. 6 is an optical microscope image of the measurement surface of TP produced by the conventional microtome method. FIG. 7 is an optical microscope image of the measurement surface of TP produced by the polishing method in the present embodiment. FIG. 8 is a flowchart for explaining the procedure of the NI measurement method in this embodiment. FIG. 9 is a plan view of the measurement holder in a state in which TP is set in the TP setting step of FIG. FIG. 10 is a cross-sectional view schematically showing how an indenter is press-fit into TP set in the measurement holder of FIG. 9. FIG. 11 is an enlarged view of a portion indicated by reference numeral XI in FIG. 10, and is a view showing the state of displacement of fibrous particles accompanying pressing-in of the indenter over time. FIG. 12 is an S-S diagram showing the measurement results of the NI method at TP of various fiber-reinforced resin materials. FIG. 13 is a graph showing the results of interfacial shear strength of TP of various fiber-reinforced resin materials obtained from the results of FIG.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its applications or its uses.

<Method of evaluating interfacial strength of fiber reinforced composite material>
FIG. 1 is a perspective view of a test piece 1 (hereinafter, referred to as “TP1”) as an evaluation sample to be measured in the interface strength evaluation method of a fiber-reinforced composite material in the present embodiment.

  TP1 is made of an automotive part K (formed product) formed using a fiber-reinforced composite material in which a large number of fibrous particles 12 are dispersed in a base material 11. The interface strength between the base material 11 and the fibrous particles 12 of such a fiber-reinforced composite material is evaluated using the NI method.

<Fiber-reinforced composite material>
The fiber reinforced composite material is, for example, a fiber reinforced resin material, a fiber reinforced ceramic material, a fiber reinforced metal material and the like. Each of these will be described below.

-Base material-
The base material 11 is for forming the shape and frame of the automobile part K. Examples of the base material 11 include resins, ceramics, metals and the like.

  As the resin, a known thermosetting resin or thermoplastic resin can be used. Specifically, for example, a polyolefin resin such as polypropylene resin (PP), maleic anhydride modified polypropylene (MAHPP) or the like, an epoxy resin (hereinafter referred to as May be referred to as "epoxy"), phenol resin, unsaturated polyester resin, vinyl ester resin, polycarbonate resin, polyester resin, polyamide (PA) resin, liquid crystal polymer resin, polyether sulfone resin, polyether ether ketone resin , Polyarylate resin, polyphenylene ether resin, polyphenylene sulfide (PPS) resin, polyacetal resin, polysulfone resin, polyimide resin, polyetherimide resin, polystyrene resin, modified polystyrene resin, AS resin Copolymer of lyl and styrene), ABS resin (copolymer of acrylonitrile, butadiene and styrene), modified ABS resin, MBS resin (copolymer of methyl methacrylate, butadiene and styrene), modified MBS resin, polymethyl methacrylate (PMMA) resin, modified Polymethyl methacrylate resin etc. are mentioned. These can be used 1 type or in mixture of 2 or more types.

  A known material can be used as the ceramic, and specific examples thereof include silicon carbide and the like.

  Specific examples of the metal include iron, copper, aluminum, titanium, stainless steel, and alloys thereof.

-Fibrous particles-
Generally, in the NI method, an indenter is pressed in the thickness direction at a measurement point of a thinly prepared evaluation sample. Therefore, in order to measure the interface strength between the base material and the particles in the evaluation sample, it is desirable that the particles be embedded in a columnar shape in the thickness direction of the evaluation sample. In other words, it is desirable that the particles contained in the composite material are fibrous.

  The fibrous particles 12 are materials added to the base material 11 mainly for the purpose of improving the strength of the composite material, and specifically, for example, glass fibers (GF), carbon fibers (CF), aramid fibers, alumina Fibers, silicon carbide fibers, boron fibers, silicon carbide fibers and the like can be mentioned. As CF, for example, polyacrylonitrile (PAN type), pitch type, cellulose type, vapor grown carbon fiber with hydrocarbon, graphite fiber and the like can be used. As GF, E glass, S glass or the like can be used. These can be used 1 type or in mixture of 2 or more types.

  The length L of the fibrous particles 12 is preferably longer than the thickness 1T of TP1 described later, from the viewpoint of securing good measurement accuracy in the NI method. The fibrous particles 12 may be continuous fibers.

  Although the shape of the cross section perpendicular | vertical to the longitudinal direction of the fibrous particle 12 is not specifically limited, Arbitrary shapes, such as circular, an ellipse, a rectangle, a polygon, can be taken. The diameter r, which is the maximum width of the cross section, is preferably larger than the size of the indenter tip, for example, 20 nm or more, from the viewpoint of securing good measurement accuracy in the NI method.

  The aspect ratio (L / r) which is the ratio of the length L to the diameter r is, for example, 5 or more, preferably 5 or more and 30 or less, from the viewpoint of securing good measurement accuracy in the NI method.

-Modifier and surface treatment-
From the viewpoint of improving the adhesion between the base material and the fibrous particles, if necessary, a modifier may be added to the base material, or the surface treatment of the fibrous particles may be performed. As a modifier, a maleic anhydride modified polypropylene (MAHPP) etc. are mentioned, for example. The surface treatment may, for example, be plasma treatment or strong acid oxidation treatment. Any of these modifier addition and surface treatment methods may be performed alone, or two or more of these may be used in combination.

-Molded product-
As a molded article which can apply the interface strength evaluation method of the fiber reinforced composite material concerning this embodiment, not only automotive parts K but parts, such as a rocket and an aircraft, sports goods, etc. are mentioned.

  The molding method is not particularly limited, and may be various known molding methods. Specifically, for example, injection molding, extrusion molding, vacuum molding, compression molding, autoclave molding, resin transfer molding (RTM) Etc.

<Production method of TP>
Hereinafter, the preparation procedure of the test piece 1 (hereinafter, referred to as “TP1”) as a sample for evaluation in the NI method will be described. As shown in FIG. 2, the production procedure of TP1 includes a cutting step S11, an embedding step S12, an attaching step S13, a polishing step S14, and a removal step S15.

-Cutting process-
First, as shown in FIG. 3, in the cutting-out step S11, the sample 13 is cut out of the automobile part K made of a fiber reinforced resin material (FIG. 2, S11).

  As shown in FIGS. 3 and 4, the shape of the sample 13 is preferably a plate shape such as a strip or a disc suitable for measurement by the NI method. As shown in FIG. 4, the sample thickness 13T, which is the thickness of the sample 13, is preferably 3 mm or more and 10 mm or less, more preferably from the viewpoint of achieving both the ease of cutting out and the efficiency of the polishing operation in the polishing step S14. Is 3.5 mm or more and 6 mm or less, particularly preferably 4 mm or more and 5 mm or less.

  As shown in FIG. 4, the sample 13 has a front surface 13A and a back surface 13B. The front surface 13A and the back surface 13B are polished in the polishing step S14 to become the measurement surface 1A and the measurement back surface 1B of TP1, respectively. The cross section of the fibrous particles 12 dispersed in the base material 11 appears on the front surface 13A and the back surface 13B.

  Further, as shown in FIG. 3 and FIG. 4, since the automotive part K is a molded product, a skin layer is formed on the surface of the core layer inside. Therefore, the sample 13 has the sample core layer 13C derived from the core layer and the sample skin layer 13D derived from the skin layer. The sample core layer 13C is exposed on the inner side of the front surface 13A and the back surface 13B.

-Embedding process-
Next, as shown in FIG. 5, the sample 13 cut out in the cutting step S11 is embedded in a protective resin 14 (resin) such as an epoxy resin or other resin that can be cured at room temperature to prepare a polishing sample 15 (FIG. 2, S12).

  Thereby, damage or the like of the polishing surface due to polishing debris or the like generated during the polishing operation of the polishing step S14 can be prevented.

  For example, when the sample 13 is a material having sufficient strength, the embedding step S12 may be omitted and the sample 13 may be directly attached to the polishing holder 17 without being embedded in the protective resin 14.

-Mounting process-
Then, the polishing sample 15 is fixed to the polishing holder 17 using the bonding material 16 (FIG. 2, S13).

  By fixing the sample 13 to the polishing holder 17, a small sample can be stably held during the polishing process, and the polishing operation becomes easy.

  For example, when the sample 13 is a material having sufficient strength, the mounting step S13 may be omitted and the sample 13 may be directly polished.

  The bonding material 16 is for fixing the polishing sample 15 to the polishing holder 17, and the bonding material 16 needs to have sufficient adhesiveness such that the polishing sample 15 is not detached from the polishing holder 17 during the polishing operation. In addition, after the polishing operation, it is necessary to easily remove the polishing sample 15 from the polishing holder 17.

  Specific examples of the bonding material 16 include paraffin and the like. The melting point of paraffin is relatively low, about 60 ° C. Therefore, it is possible to remove the polishing sample 15 from the polishing holder 17 by heating at a relatively low temperature in the subsequent removal step S15 while having sufficient adhesiveness. Thus, damage to the sample that may occur as the polishing sample 15 is desorbed to the polishing holder can be suppressed.

-Polishing process-
Next, the polishing sample 15 fixed to the polishing holder 17 is polished (FIG. 2, S14).

  Polishing of the polishing sample 15 is performed on both the front surface 13A and the back surface 13B of the sample 13.

  Both surfaces of the polishing sample 15, ie, the sample 13, are polished by a rotary polishing machine (not shown).

  The polishing conditions are determined by the required surface roughness Ra on the measurement surface 1A and the measurement back surface 1B of TP1.

  Among the polished both surfaces of TP1, at least the measurement surface 1A on the side to which the indenter in the NI method is pressed is polished to a predetermined surface roughness Ra from the viewpoint of improving the measurement accuracy by the NI method. Specifically, as for the surface roughness of the measurement surface 1A, the arithmetic mean roughness Ra is preferably 0.05 to 1.5 μm, more preferably 0.06 to 1.4 μm, particularly preferably 0.07 μm. It is 1.3 μm or less. If the surface roughness Ra is less than 0.05 μm, polishing may be difficult. If the surface roughness Ra is more than 1.5 μm, accurate measurement may be difficult because the surface accuracy is poor.

  The polishing conditions for obtaining the measurement surface 1A of the surface roughness Ra are, for example, as follows.

  First, sand paper is used to polish at a rotational speed of 120 rpm or more and 140 rpm or less. It is preferable that the sandpaper be gradually changed from the coarse one to the fine one. Specifically, for example, sandpaper of # 180 → # 240 → # 400 → # 600 is used to polish in stages. Polishing with each sandpaper is performed, for example, for about 3 minutes each.

  Thereafter, the rotational speed is reduced to 80 rpm or more and less than 120 rpm, and polishing with an alumina buff cloth is performed. Alumina is polished for about 3 minutes each using alumina of 3 μm → 0.05 μm.

  By polishing under the above-described polishing conditions, it is possible to form a polishing surface having a small surface roughness Ra as the thickness of the sample 13 becomes thinner while securing a sufficient polishing amount at the start of polishing. In addition, after rough polishing is performed by sand paper polishing, final polishing using a buff cloth with alumina can be performed to obtain a measurement surface 1A having a small surface roughness Ra. Further, as the thickness of the sample 13 becomes thinner, the rotation speed of the rotary type polishing machine can be reduced to prevent the damage and cracking of the sample 13 during polishing.

  The polishing conditions such as the type of polishing machine, the polishing speed and time, and the type of polishing agent described above are not particularly limited, and any polishing conditions may be used as long as the predetermined surface roughness Ra can be obtained. May be adopted.

  Moreover, surface roughness Ra of measurement back surface 1B of TP1 becomes like this. Preferably it is 2.0 micrometers or less, More preferably, it is surface roughness Ra equivalent to measurement surface 1A. The range of allowable surface roughness Ra is wider than that of the measurement surface 1A where the measurement back surface 1B is in direct contact with the indenter. However, since TP1 used for measurement in the NI method is extremely thin, not only the measurement surface 1A on which the indenter 2 is pressed in, but also the surface roughness Ra of the measurement back surface 1B opposite to the measurement surface 1A affects the measurement accuracy. Can exert Therefore, the measurement accuracy can be improved by polishing the surface roughness Ra of the measurement back surface 1B to the same surface roughness Ra as that of the measurement surface 1A.

  The polishing conditions for obtaining the measurement back surface 1B of the surface roughness Ra are such that when the surface roughness Ra of the measurement back surface 1B is allowed to be larger than the surface roughness Ra of the measurement surface 1A, The conditions can be made simpler than the polishing conditions. Specifically, for example, using the same polishing agent as the polishing condition of the measurement surface 1A, the polishing time of about 3 minutes can be shortened to, for example, the polishing time of about 1 minute. In addition, polishing may be performed under conditions simpler than that of the measurement surface 1A by reducing the types of the size of the sandpaper eyes and the alumina particles. Further, as described above, in the case of obtaining the surface roughness Ra equivalent to the measurement surface 1A also for the measurement back surface 1B, it is preferable to polish under the same conditions as the measurement surface 1A.

  Although either side of the sample 13 may be polished first, it is preferable to polish the surface 13A after polishing the back surface 13B. That is, first, the back surface 13B is polished to form the measured back surface 1B of TP1. Then, after the polishing sample 15 is removed from the polishing holder 17 by the same method as the subsequent removal step S15, the back surface of the sample 13, ie, the measurement back surface 1B side of TP1 is attached to the polishing holder 17, and the front surface 13A of the sample 13 Is ground to form a measurement surface 1A.

  Then, since it is not necessary to fix measurement surface 1A to polishing holder 17, the possibility of contamination of measurement surface 1A of TP1 can be reduced.

-Removal process-
In the removal step S15, the polishing holder 17 is heated to about 60 ° C. to about 70 ° C., and the bonding material 16 disposed between the TP1 and the polishing holder 17 is melted to remove the TP1 from the polishing holder 17 ( Figure 2, S15).

  Thus, the TP1 can be easily removed from the polishing holder 17, and damage to the measurement surface 1A and the measurement back surface 1B, which are the polishing surface of the TP1 associated with the removal operation, can be suppressed.

  When the sample 13 is embedded in the protective resin 14 and the polishing sample 15 is polished in the embedding step S12, the protective resin 14 is removed after removing the sample 13 from the polishing holder 17, and the TP1 is taken out. Then, TP1 is washed and dried, and subjected to measurement by the NI method.

-About TP-
As shown in FIG. 1, TP1 has a polished measurement surface 1A and a measurement back surface 1B. The cross section of the fibrous particles 12 dispersed in the base material 11 is visible on the measurement surface 1A and the measurement back surface 1B. Further, the inside of TP1 is a TP core layer 1C derived from the core layer, and the outer peripheral portion is a TP skin layer 1D derived from a skin layer.

  The TP thickness 1T (thickness of the evaluation sample), which is the thickness of TP1 obtained in the polishing step S14, is thin enough to be measured by the NI method, and TP1 with a sufficiently small surface roughness Ra is obtained. From the viewpoint, it is preferably 50 μm or more and 200 μm or less, more preferably 50 μm or more and 150 μm or less, and particularly preferably 50 μm or more and 120 μm or less. In other words, the TP thickness 1T is preferably 0.5% or more and 7% or less of the sample thickness T13 of the sample 13. By polishing the sample 13 to such a thickness, it is possible to obtain an evaluation sample which has not been damaged in the cutting process.

  6 and 7 show measurement surfaces (Comparative Example 1) of TPs prepared by the conventional microtome method of CF reinforced PP materials (CF / PP) in which the base material 11 is PP and the fibrous particles 12 are CF. The optical microscope image of measurement surface 1A (Example 1) of TP1 produced by the grinding | polishing method in this embodiment is shown.

  As shown in FIG. 6, in the measurement plane of Comparative Example 1, deformation of CF is remarkable, and it is difficult to clearly distinguish the cross section of CF. In addition, it is understood that the unevenness of the PP surface is also remarkable.

  On the other hand, as shown in FIG. 7, in the measurement surface 1A of the first embodiment, it is possible to clearly distinguish a cross section close to a circle of CF. It can also be seen that the PP surface is also generally smooth.

  The arithmetic mean surface roughness Ra in the solid line portion of FIGS. 6 and 7 was 1.69 μm in FIG. 6 and 0.16 μm in FIG.

  In the TP of Comparative Example 1 of FIG. 6, when scraped, unnecessary stress is applied to the TP, causing deformation of CF and PP, and it is considered that the surface roughness Ra of TP is increased. On the other hand, in TP1 of Example 1 of FIG. 7, it was found that the surface roughness Ra was about 10 times smaller than that of the microtome method of FIG.

<Evaluation procedure of interface strength>
Hereinafter, a procedure for evaluating the interfacial strength between the base material and the fibrous particles by the NI method using TP1 will be described. As shown in FIG. 8, the evaluation procedure includes a TP setting step S21 (arrangement step) and an evaluation step S25.

-TP set process-
As shown in FIG. 8, in the TP setting step S21 (arrangement step), TP1 obtained after the removal step S15 is placed on the measurement holder 5. In addition, as shown in FIG. 10, the measurement holder 5 consists of the sample stand 4 and the jig | tool 3 (mounting part) arrange | positioned on it.

  In the measurement of the NI method, the measurement point of TP1 is displaced in the press-fitting direction by the press-fitting of the indenter 2. Therefore, as shown in FIG. 9, in the jig 3 on which TP1 is placed, measurement holes are formed at positions corresponding to the measurement points so as not to prevent the displacement of TP1. That is, the jig 3 is provided with a plurality of measurement holes 31A, 31B, 31C, 31D, 31E, 31F (hereinafter, these measurement holes may be collectively referred to as "measurement holes 31"). .

  In particular, the measurement holes 31A, 31E, 31F are provided close to each other so as to evaluate the interface strength at a plurality of positions in the same TP1. The measurement hole 31A is for evaluating the interface strength of the central portion of the TP core layer 1C of TP1. The measurement hole 31E is provided for interface strength evaluation in the vicinity of the TP skin layer 1D of TP1. Furthermore, the measurement holes 31F are provided to continuously evaluate the interface strength at a plurality of positions from the TP core layer 1C to the TP skin layer 1D. By placing one TP 1 so as to cover a plurality of measurement holes 31, the interface strength of the fiber-reinforced composite material can be measured at a plurality of measurement points in one TP1. Then, for example, it becomes possible to evaluate the difference in interface strength between the TP core layer 1C and the TP skin layer 1D in one TP1.

  The maximum diameter of the measurement hole 31 is preferably 0.5 mm or more and 2 mm or less, more preferably 0.7 mm or more and 1.5 mm from the viewpoint of obtaining good measurement accuracy while suppressing excessive deformation of TP1 by press-fitting the indenter 2. It is below. Measurement holes 31A, 31C and 31E shown in FIG. 9 are circular with a diameter of 1 mm, measurement holes 31B and 31D are circular with a diameter of 2 mm, and measurement hole 31F is an oval with a maximum diameter of 1.5 mm. The shape of the measurement hole 31 is not particularly limited and may take various shapes such as circular, oval, oval, rectangular, polygonal, etc. However, the distance from the outer peripheral edge of the measurement hole 31 to the measurement position is made uniform From the viewpoint of suppressing excessive deformation of TP1, circular, oval and elliptical are preferable.

  The thickness of the jig 3 can be set to, for example, 1 mm to 5 mm from the viewpoint of securing good measurement accuracy while suppressing excessive deformation of TP1 in the NI method.

-Evaluation process-
Evaluation process S25 is a process of pressing the indenter 2 into the surface of TP1 arrange | positioned at the measurement holder 5, and evaluating the interfacial strength of a fiber reinforced composite material. Evaluation process S25 is provided with press process S22, interface peeling process S23, and contact process S24 as shown in FIG.

  In the NI method, as shown in FIG. 10, for the TP1 placed on the jig 3, for example, the indenter 2 is pressed into a portion of the jig 3 located above the measurement hole 31A. An enlarged view of an indenter press-in portion indicated by reference numeral XI in FIG. 10 is shown in FIG.

  FIG. 11 (a) shows that the indenter 2 is in contact with the cross section of the fibrous particles 12 of TP1. Thereafter, when the press-in of the indenter 2 is started, as shown in FIG. 11 (b), the fibrous particles 12 are displaced downward while the interface between the base material 11 and the fibrous particles 12 is in the adhered state (FIG. 8, Pressing step S22).

  Eventually, when the press-fit of the indenter 2 proceeds, as shown in FIG. 11C, the adhesion of the interface between the base material 11 and the fibrous particles 12 is peeled off (FIG. 8, interface peeling step S23). Then, the fibrous particles 12 are pushed out of the base material 11, and as shown in FIG. 11 (d), the measurement can be ended when the indenter 2 contacts the base material 11 (FIG. 8, contact step S24). .

  FIG. 12 shows the results of measuring the interface strength between the base material 11 and the fibrous particles 12 by the method for evaluating the interface strength of a fiber-reinforced composite material according to this embodiment for TP1 of various fiber-reinforced resin materials. That is, FIG. 11 is an SS diagram plotting interface stress (MPa) with respect to interface strain (%) as the press-fit depth of the indenter 2 when the state of (a) is 0% in FIG.

  As fiber-reinforced resin materials, CF / PP of Example 1, CF-reinforced epoxy resin of Example 2 (CF / epoxy), GF-reinforced PP resin of Example 3 not containing MAHPP (GF / PP, without MAHPP), and The measurements were carried out on four types of GF-reinforced PP resin (GF / PP MAHPP present) containing MAHPP of Example 4.

  As shown in FIG. 12, in any of the fiber-reinforced resin materials of Examples 1 to 4, a region where the interface stress is constant was clearly confirmed. This region shows the state of FIG. 11 (c), and the interface stress at this time indicates the interface shear strength.

  The interface shear strength of each fiber-reinforced resin material is determined from the value of interface stress in the above region of FIG. 12, and the result is shown in FIG. With respect to the interfacial shear strength, in the fiber-reinforced resin material containing CF as the fibrous particles 12 of Examples 1 and 2, the interfacial shear strength of the CF / epoxy of Example 2 is higher than that of the CF / PP of Example 1. It was found that the epoxy was higher in adhesion to CF than PP. Further, in the fiber-reinforced resin materials containing GF of Examples 3 and 4, the GF / PP MAHPP having Example 4 had about 4 times the interfacial shear strength as compared with the GF / PP MAHPP without Example 3. It turned out to be high. It is considered that this is because the adhesive layer of MAHPP is formed at the interface between GF and PP by containing MAHPP.

  As described above, according to the method for evaluating the interfacial strength of a fiber-reinforced composite material according to the present embodiment, the interfacial strength between the base material 11 of the fiber-reinforced composite material and the fibrous particles 12 can be evaluated accurately. Moreover, since TP can be produced from the product after shaping | molding and the interfacial strength of the base material 11 and the fibrous particle 12 can be evaluated, highly reliable evaluation can be performed. Furthermore, the fatigue condition etc. of the product can be evaluated by performing the evaluation over time.

  The present invention is extremely useful because it can obtain a thin evaluation sample of surface roughness Ra suitable for measurement by the NI method, and can improve measurement accuracy by the NI method.

1 Test piece, TP (sample for evaluation)
1A Measurement surface 1B Measurement back surface 1C TP core layer 1D TP skin layer 1T TP thickness (thickness of sample for evaluation)
Reference Signs List 2 indentation 3 jig 4 sample stage 5 measurement holder 11 base material 12 fibrous particles 13 sample 13A front surface 13B back surface 14 protective resin (resin)
15 Polishing Sample 16 Bonding Material 17 Polishing Holder 31, 31A, 31B, 31C, 31D, 31F Measurement Hole S11 Cutting Step S12 Embedding Step S13 Mounting Step S14 Polishing Step S15 Removal Step S21 TP Setting Step (Arranging Step )
S22 Pressing Step S23 Interface Peeling Step S24 Contact Step S25 Evaluation Step K Automotive Parts (Molded Parts)

Claims (10)

This is a method for evaluating the interfacial strength of a fiber-reinforced composite material, wherein the interfacial strength between the fibrous material and the matrix of the fiber-reinforced composite material in which fibrous particles are dispersed in the matrix and the fibrous particles is evaluated using a nanoindentation method. ,
A cutting step of cutting a plate-like sample from the molded article of the fiber reinforced composite material;
Polishing both surfaces of the sample to obtain an evaluation sample;
Among the polished surfaces of the evaluation sample in the polishing step, the measurement surface on the side to which the indenter is pressed in in the nanoindentation method is polished to a predetermined surface roughness Ra .
In the polishing step, of both sides of the sample, the back surface is polished to form the measurement back surface of the evaluation sample, and then the surface of the sample is polished to polish the measurement surface. A method of evaluating the interfacial strength of a fiber-reinforced composite material as a feature. In claim 1,
Surface roughness Ra of the said measurement surface of the said sample for evaluation is 0.05 micrometer or more and 1.5 micrometers or less, The interface strength evaluation method of the fiber reinforced composite material characterized by the above-mentioned. In claim 2,
Among the polished surfaces of the evaluation sample in the polishing step, the measured back surface opposite to the measurement surface is also polished until the surface roughness Ra is 0.05 μm or more and 1.5 μm or less. Method for evaluating interfacial strength of fiber reinforced composite material characterized by In any one of claims 1 to 3 ,
The thickness of the sample for evaluation is a thickness of 0.5% or more and 7% or less of the sample, and the interface strength evaluation method of a fiber reinforced composite material. In claim 4 ,
The thickness of the sample cut out in the cutting step is 3 mm or more and 10 mm or less,
The thickness of the said sample for evaluation obtained at the said grinding | polishing process is 50 micrometers or more and 200 micrometers or less, The interface strength evaluation method of the fiber reinforced composite material characterized by the above-mentioned. In any one of claims 1 to 5 ,
After the cutting step and before the polishing step
Embedding the sample into the resin;
And a mounting step of fixing the sample embedded in the resin to a polishing holder using a bonding material,
A method of evaluating interfacial strength of a fiber-reinforced composite material, characterized in that the sample embedded in the resin and fixed to the polishing holder is polished in the polishing step. In claim 6 ,
The method further comprises a removal step of removing the evaluation sample from the polishing holder after the polishing step,
A fiber reinforced composite material characterized in that, in the removal step, the evaluation sample is removed from the polishing holder by heating and melting a bonding material disposed between the evaluation sample and the polishing holder. Interface strength evaluation method. This is a method for evaluating the interfacial strength of a fiber-reinforced composite material, wherein the interfacial strength between the fibrous material and the matrix of the fiber-reinforced composite material in which fibrous particles are dispersed in the matrix and the fibrous particles is evaluated using a nanoindentation method. ,
A cutting step of cutting a plate-like sample from the molded article of the fiber reinforced composite material;
Polishing both surfaces of the sample to obtain an evaluation sample;
Among the polished surfaces of the evaluation sample in the polishing step, the measurement surface on the side to which the indenter is pressed in in the nanoindentation method is polished to a predetermined surface roughness Ra.
After the cutting step and before the polishing step
Embedding the sample into the resin;
And a mounting step of fixing the sample embedded in the resin to a polishing holder using a bonding material,
Polishing the sample embedded in the resin and fixed to the polishing holder in the polishing step;
The method further comprises a removal step of removing the evaluation sample from the polishing holder after the polishing step,
In the removal step, the evaluation sample is removed from the polishing holder by heating and melting a bonding material disposed between the evaluation sample and the polishing holder.
The method for evaluating the interfacial strength of a fiber-reinforced composite material, wherein the bonding material is paraffin. In any one of claims 1 to 8 ,
In the polishing step, at least the measurement surface among the polished surfaces of the evaluation sample is polished with sand paper at a rotational speed of 120 rpm or more and 140 rpm or less by a rotary type polishing machine, then alumina is applied at a rotational speed of 80 rpm or more and less than 120 rpm The interface strength evaluation method of the fiber reinforced composite material characterized by being formed by grinding | polishing by buff cloth. This is a method for evaluating the interfacial strength of a fiber-reinforced composite material, wherein the interfacial strength between the fibrous material and the matrix of the fiber-reinforced composite material in which fibrous particles are dispersed in the matrix and the fibrous particles is evaluated using a nanoindentation method. ,
A cutting step of cutting a plate-like sample from the molded article of the fiber reinforced composite material;
Polishing both surfaces of the sample to obtain an evaluation sample;
Among the polished surfaces of the evaluation sample in the polishing step, the measurement surface on the side to which the indenter is pressed in in the nanoindentation method is polished to a predetermined surface roughness Ra.
After the polishing step,
An arrangement step of arranging the evaluation sample in a measurement holder;
An evaluation step of evaluating the interface strength of the fiber-reinforced composite material by pressing the indenter into the measurement surface of the evaluation sample disposed in the measurement holder;
The mounting portion on which the evaluation sample of the measurement holder is mounted is provided with a plurality of measurement holes so as to evaluate interface strength at a plurality of positions of the evaluation sample. Interface strength evaluation method for fiber reinforced composite materials.