TW202337862A - Glass fiber - Google Patents

Abstract

A glass fiber according to the present invention contains SiO2 that forms a glass skeleton, Al2O3 and MgO; and this glass fiber has cracking resistance.

Description

fiberglass

The present invention relates to glass fiber, glass fiber materials using the same, and resin-impregnated fiber materials.

Glass fibers have a high elastic modulus and can therefore be used in various fields. For example, as shown in Patent Document 1, they are sometimes used to regenerate existing pipes.

Prior technical literature patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-11904

The problem to be solved by the invention In addition to being used in the construction of the above-mentioned pipes, the glass fiber is also used for various purposes. For example, it is sometimes used in objects that move frequently such as windmill blades. The moving objects may sometimes be impacted by collisions with other objects, etc., and cracks may occur when the objects are impacted. However, research on crack resistance has not been sufficient, and a glass fiber with high crack resistance is desired. The present invention was developed to solve this problem, and its purpose is to provide glass fiber, glass fiber material, and resin-impregnated fiber material with high crack resistance.

Means for Solving the Problem Item 1. A glass fiber containing: SiO ₂ forming a glass skeleton; Al ₂ O ₃ ; and MgO; and the glass fiber has crack resistance.

Item 2. The glass fiber as in Item 1, wherein the SiO ₂ content is more than 55 mol%.

Item 3. The glass fiber according to Item 1 or 2, wherein the aforementioned MgO content is 30 mol% or less.

Item 4. The glass fiber according to any one of Items 1 to 3, with an elastic modulus of 90 GPa or more.

Item 5. The glass fiber according to any one of Items 1 to 4, which further contains a rare earth compound.

Item 6. The glass fiber according to any one of Items 1 to 5 has a crack resistance load of more than 400g.

Item 7. A fiberglass material formed from the glass fiber of any one of Items 1 to 6, And the glass fiber material is in any form of strands, cut strands, yarns and rovings.

Item 8. A resin-impregnated fiber material, having: Glass fiber material, which is formed from the glass fiber in any one of items 1 to 6, and the glass fiber material is in any form of woven fabric or non-woven fabric; and Resin is infiltrated into the aforementioned glass fiber material.

Item 9. The resin-impregnated fiber material as described in Item 8 is used as a blade of a windmill for wind power generation, a blade of a helicopter, a blade of an unmanned aerial vehicle, or a high-pressure tank structure.

Invention effect According to the present invention, high crack resistance can be achieved.

The embodiments of the glass fiber of the present invention will be described as embodiments for carrying out the invention. The glass fiber of the present invention contains at least SiO ₂ , Al ₂ O ₃ , and an elastic modulus adjusting component for increasing the elastic modulus. This will be explained in detail below. The following symbols indicating the content of glass components, %, are molar % unless otherwise specified.

<1. Glass fiber component><1-1. SiO ₂ > SiO ₂ is the main component of glass fiber, that is, a component that forms the glass skeleton, and its content is set to a range of, for example, 50 to 70%. The SiO ₂ content is preferably 55% or more, more preferably 60% or more, especially 62% or more. If the SiO ₂ content is too low, crack resistance and acid resistance may decrease. On the other hand, if the SiO ₂ content is too high, the elastic modulus (for example, Young's modulus) may decrease. Therefore, the SiO ₂ content is preferably 67% or less, more preferably 65% or less, 63% or less, and especially 60% or less.

<1-2.Al ₂ O ₃ > Al ₂ O ₃ contributes to maintaining the heat resistance, water resistance, etc. of the glass composition, and is also a component that affects the devitrification temperature, viscosity, etc. In particular, Al ₂ O ₃ contributes to increasing the crack resistance load described below. Therefore, the Al ₂ O ₃ content is set in the range of 10 to 26%. The Al ₂ O ₃ content rate is preferably 10% or more, more preferably 12% or more, especially 15% or more. Depending on the situation, it may be 16% or more, and further, it may be 17% or more. If the Al ₂ O ₃ content rate is too high, the liquidus temperature may rise significantly, which may cause manufacturing problems. Therefore, the Al ₂ O ₃ content is preferably 24% or less, more preferably 22% or less, and depending on the situation, it may be 20% or less, and further may be 19% or less.

Especially when considering mass production, the devitrification temperature of the glass composition should be sufficiently lower than the liquidus temperature. In order to sufficiently lower the devitrification temperature lower than the liquidus temperature, the appropriate Al ₂ O ₃ content is 11 to 15%, further 11 to 14%, and 11.5 to 13.5% is particularly suitable. As will be described later, in order to sufficiently lower the devitrification temperature lower than the liquidus temperature, an appropriate amount of Li ₂ O and/or B ₂ O ₃ may be added.

<1-3. Component for increasing elastic modulus> The glass fiber of the present invention contains MgO as an elastic modulus adjusting component for increasing elastic modulus. In addition, alkaline earth metal compounds, rare earth compounds, etc. may be further included as other elastic modulus adjusting components. Examples of alkaline earth metal compounds include MgO, CaO, and the like. Examples of rare earth compounds include Y ₂ O ₃ , La ₂ O ₃ , and CeO ₂ . In addition, the elastic modulus adjusting component only needs to contain at least one kind of composition, and may contain two or more kinds of compositions. This is explained below. (MgO) MgO helps to increase the elastic modulus (such as Young's modulus), and is also a component that affects the devitrification temperature, viscosity, etc. In addition, MgO contributes to increasing the crack resistance load described below. Therefore, the MgO content rate can be set in the range of 15 to 30%, for example. The MgO content rate is preferably 17% or more, more preferably 18% or more, especially 20% or more. Depending on the situation, it may be 21% or more, and further it may be 22% or more. If the MgO content rate is too high, the liquidus temperature may rise significantly. Therefore, the MgO content rate is preferably 35% or less, more preferably 30% or less, and depending on the situation, it may be 28% or less, and further may be 25% or less.

In order to sufficiently lower the devitrification temperature lower than the liquidus temperature, the appropriate MgO content is 18 to 30%, and further 20 to 28%.

(CaO) CaO is an arbitrary component. In addition to adjusting the elastic modulus (such as Young's modulus), it also helps maintain water resistance, etc., and affects the devitrification temperature, viscosity, etc. The CaO content rate can be set in the range of 0 to 8%, for example. Adding an appropriate amount of CaO is suitable from the viewpoint of lowering the liquidus temperature. Therefore, it is appropriate to add CaO (content rate is greater than 0%), and its content rate is preferably 0.1% or more, more preferably 0.12% or more, and depending on the situation, it can be 2% or more, and further it can be 3% or more. However, too much CaO sometimes reduces Young's modulus and acid resistance. Therefore, the CaO content is preferably 7% or less, more preferably 5% or less. In order to improve Young's modulus and crack resistance load, the particularly suitable CaO content is less than 1%.

(Total of MgO and CaO) The total content of MgO and CaO is set to 18% to 35%, preferably in the range of 20% to 30%.

(Al ₂ O ₃ /(MgO+CaO)) The molar ratio of Al ₂ O ₃ to the total content of MgO and CaO can be set to less than 1. This makes it easy to achieve both a high Young's modulus and a liquidus temperature that is not too high. The molar ratio Al ₂ O ₃ /(MgO+CaO) is preferably 0.3~0.9, especially 0.35~0.85. Depending on the situation, it may also be 0.4~0.7, and further it may be in the range of 0.4~0.6. However, the molar ratio Al ₂ O ₃ /(MgO+CaO) which is particularly suitable for improving the crack resistance load is 0.7 or more and less than 1, further 0.7 or more and 0.9 or less, and 0.8 or more and 0.9 or less is particularly suitable.

(MgO/RO (total amount of alkaline earth metal compounds)) It is known that if the ratio of MgO/RO is increased, the acid resistance performance will be improved. For example, MgO/RO should be 0.5 or more, and more preferably 0.7 or more.

(Rare Earth Compound) As mentioned above, examples of the rare earth compound include Y ₂ O ₃ , La ₂ O ₃ , and CeO ₂ . The rare earth compound content rate can be set in the range of 0 to 8%, for example. The rare earth compound content is preferably 0.1% or more, more preferably 1% or more, especially 3% or more. If the content rate of the rare earth compound is too high, the acid resistance may be weakened and the batch cost may increase. Therefore, the rare earth compound content is preferably 8% or less, and more preferably 6% or less.

＜1-4.Other ingredients＞ In the glass fiber of the present invention, in addition to the above-mentioned components, the following components may also be added as required. However, it is not limited to the following components, and components other than these may be added appropriately.

(ZrO ₂ ) ZrO ₂ is a component used to improve acid resistance. The ZrO ₂ content rate can be set in the range of 0.1 to 3%, for example. The ZrO ₂ content is preferably 0.1% or more, more preferably 0.3% or more, especially 0.5% or more. If the ZrO ₂ content is too high, the glass may crystallize easily, resulting in devitrification. Therefore, the ZrO ₂ content is preferably 3% or less, and more preferably 1.5% or less.

(TiO ₂ ) TiO ₂ is a component used to improve acid resistance. The TiO ₂ content rate can be set in the range of 0.1 to 3%, for example. The TiO ₂ content is preferably 0.1 to 3% or more, more preferably 0.3% or more, especially 0.5% or more. If the TiO ₂ content is too high, the uniformity of the glass will be lost, and devitrification may also occur in this case. Therefore, the TiO ₂ content is preferably 3% or less, and more preferably 1.5% or less.

(B ₂ O ₃ ) B ₂ O ₃ is an arbitrary component that forms the skeleton of glass and affects properties such as devitrification temperature and viscosity. The B ₂ O ₃ content rate is set in the range of 0 to 3%. Adding trace amounts of B ₂ O ₃ sometimes helps reduce the devitrification temperature. Therefore, B ₂ O ₃ can also be added (the content rate is greater than 0%). When B ₂ O ₃ is added, the content rate is preferably 0.1% or more, especially 0.3% or more, and it can also be 0.5% or more depending on the situation. Further It can also be above 0.7%. However, too much B ₂ O ₃ sometimes reduces the Young's modulus. The B ₂ O ₃ content is preferably 2.5% or less, more preferably 2% or less, especially 1.8% or less. Depending on the situation, it may be 1.6% or less, and further may be 1.5% or less. An example of a preferable range of B ₂ O ₃ content is 0.1 to 1.6%.

(Li ₂ O) Li ₂ O is a component that modifies the glass skeleton and is an arbitrary component that affects characteristics such as liquidus temperature, devitrification temperature, and viscosity. The Li ₂ O content is set in the range of 0 to 3%. Adding Li ₂ O in this range can effectively reduce the devitrification temperature. Therefore, Li ₂ O (content rate is greater than 0%) can also be added. When Li ₂ O is added, the content rate is preferably 0.1% or more, more preferably 0.2% or more, especially 0.3% or more. Depending on the situation, it can also be 0.5% or more, and further 0.7% or more. If the Li ₂ O content rate is too high, the Young's modulus may decrease. Therefore, the Li ₂ O content is preferably 2.5% or less, more preferably 2% or less, especially 1.8% or less. Depending on the situation, it may be 1.6% or less, and further may be 1.5% or less. An example of a preferable range of the Li ₂ O content is 0.2 to 2.5%, which is a higher range than the Na ₂ O content.

(Na ₂ O) Na ₂ O and Li ₂ O are also arbitrary components that affect liquidus temperature, devitrification temperature, viscosity and other characteristics. However, since Na ₂ O has a greater effect of reducing the Young's modulus than Li ₂ O, its content is set in the range of 0 to 0.2%. Although it is basically desirable not to contain Na ₂ O, in order to clarify the glass melt, it is advisable to add it within 0.2%, and more preferably within 0.15%. For example, it is advisable to add it within the range of more than 0% and less than 0.1%. Add to.

In addition, in this specification, the content of oxides of transition elements (ZrO ₂ , Y ₂ O ₃ , La ₂ O ₃ , CeO _2, etc.) with several valences present in the glass fiber is converted into the metal. The oxidation number is the largest oxide.

(Total of the above-described components) The total content rate of the above-described components (SiO ₂ , Al ₂ O ₃ , MgO) is preferably 95% or more, more preferably 97% or more, especially 98% or more. It is preferably above 99%, and may be 99.5% depending on circumstances. It may further be greater than 99.9%, or may be 100%.

＜2.Characteristics of glass fiber＞ ＜2-1. Elastic modulus＞ In one embodiment of the present invention, the elastic modulus of the glass fiber can be measured by Young's modulus. The Young's modulus is preferably above 90 GPa, more preferably above 95 GPa, especially above 100 GPa. The upper limit of Young's modulus is not particularly limited, and may be 110 GPa or less. Young's modulus is not measured using glass fibers, but is measured using bulk glass with the same composition in the following manner.

Young's modulus is measured according to the ultrasonic pulse method described in Japanese Industrial Standards (JIS) R1602-1995. Each test piece is determined to be a rectangular parallelepiped of 5mm×25mm×35mm. In addition, the measurement was performed at room temperature and in the air, and the measurement device was model 25DLPlus manufactured by Panametrics.

In addition, it is known that in glass fibers and bulk glass composed of the same glass composition, the glass fibers usually have a relatively low elastic modulus. It is thought that this is because the glass fiber is greatly and rapidly cooled when it is formed from the glass melt. However, there is a positive correlation between the elastic modulus of glass fiber and the elastic modulus of bulk glass (the elastic modulus measured according to the above-mentioned JIS). Therefore, it is necessary to use the measured value according to the above-mentioned JIS to evaluate glass fiber or use The properties of the glass composition used to make glass fiber are very suitable.

＜2-2. Crack resistance load＞ In the present invention, cracks are less likely to occur when receiving an impact from the outside, that is, crack resistance was evaluated. Crack resistance load can be used as an indicator of crack resistance. Specifically, the crack resistance load of the glass fiber is, for example, 300g or more, preferably 400g or more, more preferably 500g or more. Surprisingly, according to one embodiment of the present invention, a glass composition with a particularly high crack resistance load can be provided. The crack resistance load is, for example, 900g or more, further 1000g or more, especially 1200g or more. The upper limit of the crack resistance load is not particularly limited, and may be 2000g or less.

The crack resistance load is measured by pressing a Vickers indenter against the mirror-polished sample glass surface. The device used is a Vickers hardness tester manufactured by Akashi Seisakusho. The sample glass is processed into a plate shape with parallel planes. Furthermore, a suspension of cerium oxide abrasive is used to grind the surface against which the pressure head is pressed into a mirror surface. Press the Vickers indenter against the mirror-polished surface for 15 seconds and remove it for 5 minutes. Then, measure the square indentation remaining on the surface of the sample glass to see whether there are cracks from the vertex of the indentation. Whether cracks have occurred or not can be judged by observation using a microscope integrated into the Vickers hardness tester. The magnification of the microscope is 100 times. This measurement is performed 10 times, and the crack occurrence probability P is calculated by dividing the number of vertices at which cracks occur by the total number of measured vertices (40). Repeat the above measurement by changing the load in the order of 50g, 100g, 200g, 300g, 500g, 1000g, and 2000g until P=100% is reached, and find the crack occurrence probability P under each load. By proceeding in the above manner, the two adjacent loads WH and WL spanning P=50%, and the crack generation probabilities PH and PL at this time (PH<50%<PL) are obtained. Let the load and crack occurrence probability be the horizontal axis and the vertical axis respectively, and draw a straight line passing through two points (WH, PH) and (WL, PL), and define the load of P = 50% as the crack resistance load. Crack resistance can be mainly divided into two factors. One is for impact resistance. The so-called impact resistance is a factor related to whether glass fiber is easily damaged. They will also depend on the shape of the glass fibers, the shape of the strands made of the glass fibers, and the manufacturing steps of the glass fibers and strands. Another factor is fracture toughness. Fracture toughness refers to the material's resistance to fracture when a mechanical load is applied to a material with crack-like defects. It can be said that the greater the fracture toughness, the higher the crack resistance. In the present invention, regarding the crack resistance and fracture toughness, particular attention is paid to the relationship between the crack resistance and the glass composition.

＜2-3. Acid resistance performance＞ In one embodiment of the present invention, the acid resistance performance of the glass fiber can be evaluated, for example, according to the method of JOGIS J06-1999. That is, the specific gravity of the crushed glass fiber is put into a platinum vessel, immersed in 80 ml of sulfuric acid solution with a specific gravity of 1.2 in the flask, heated at 99°C for 60 minutes, and then dried at 120°C. Weigh and determine the reduction rate. As a result, the weight loss rate is preferably 0.2% or less.

＜3. Manufacturing method of glass fiber＞ The above-mentioned glass fiber can be produced by making the glass melt with controlled viscosity flow out from the nozzle and coiling it by a coiler. The continuous fiber can be cut into appropriate lengths during use. Short glass fibers can be produced by ejecting molten glass using high-pressure air, centrifugal force, etc.

＜4.Glass fiber material＞ The glass fiber of the present invention can be applied to various forms of glass fiber materials. For example, a plurality of glass fibers can be bundled into strands. Each strand can be composed of, for example, 100 to 10,000 glass fibers, and typically is composed of 200 to 4,000 glass fibers. In addition, it is also possible to form strands in which the strands are cut into predetermined lengths. The cutting length is not particularly limited, for example, it can be set to 1~25mm, preferably 2~11mm, more preferably 3~6mm.

Alternatively, a yarn can be formed by twisting a plurality of glass fibers to form a twisted yarn. Alternatively, a roving composed of a plurality of glass fibers can be formed. Further, a plurality of glass fibers can be used to form a woven fabric. At this time, weaving methods such as plain weave, twill weave, leno weave, and braided cloth can be applied. Alternatively, multiple glass fibers can be used to form a non-woven fabric. In addition, a mat with voids formed by randomly gathering glass fibers can also be formed.

＜5. Resin-impregnated fiber material＞ The above-mentioned glass fibers can be applied to resin-impregnated fiber sheets. The resin-impregnated fiber sheet is a sheet made by using the above-mentioned glass fiber to form woven fabric, non-woven fabric or fiber bundle, and then impregnating the resin into it.

The resin impregnated into the resin-impregnated fiber sheet is not particularly limited, and for example, thermosetting resin, thermoplastic resin, and photocurable resin can be used. Examples of the thermosetting resin include resins such as urethane resin, vinyl ester resin, and epoxy resin. Examples of the thermoplastic resin include polyethylene resin, polypropylene resin, polypropylene copolymer, nylon resin, polymethacrylic resin, polyvinyl chloride resin, and polycarbonate resin. Examples of the photocurable resin include ultraviolet curable resins that can be cured by irradiation with ultraviolet rays. As the resin impregnated into the resin-impregnated fiber sheet, only one type of resin may be used, or a plurality of types of resin may be mixed and used.

The thickness of the resin-impregnated fiber sheet is not particularly limited, but can be set to 1 to 10 mm, for example. In addition to being formed into a sheet shape, it can also be formed into various shapes such as a block shape by laminating a plurality of sheets.

＜6.Uses of resin-impregnated fiber materials＞ <6-1. Blade components> As a blade member, it can be applied to, for example, a blade member of a windmill for wind power generation, a blade member of a helicopter propeller, a blade member of a drone propeller, etc. For the uses of the blade components listed here, in addition to having a high elastic modulus, since the component will move frequently, there is a risk of collision with foreign objects, and crack resistance is required.

As shown in FIG. 1 , the blade member 5 includes an attachable mounting portion 51 for mounting on the rotation shaft, and a blade body 52 extending from the mounting portion 5 . The blade body 52 is formed by an outer skin 521 and a core material 522 , and the core material 522 is disposed in an internal space surrounded by the exterior 521 . The outer skin 521 is formed of at least one layer of resin-impregnated fiber sheets. As the resin-impregnated fiber sheet, in addition to the above-mentioned glass fiber, a fiber including carbon fiber, aramid fiber, etc. can also be used. For example, at least one layer of resin-impregnated glass fiber sheets and at least one layer of resin-impregnated carbon fiber sheets may be laminated to form the outer skin 521 . In this case, by arranging the resin-impregnated carbon fiber sheet on the inside and the resin-impregnated glass fiber sheet on the outside, the impact resistance against external impacts can be improved. Alternatively, the outer skin 521 may be composed of only resin-impregnated glass fiber sheets.

The composition of the core material 522 is not particularly limited. For example, it can be composed of a truss extending into a rod shape and a foam material arranged around the truss.

By forming the outer skin 521 in the above manner, the following effects can be obtained. For example, if only resin-impregnated carbon fiber sheets are used to form the outer skin, although the high elasticity of the carbon fiber can ensure the strength against load, there will be a problem of being weak in impact. In addition, the glass fiber of the conventional resin-impregnated glass fiber sheet has a problem of low impact resistance. Therefore, if the resin-impregnated glass fiber sheet is formed from the impact-resistant and highly elastic glass fiber strands as described above, the strength with respect to the load can be ensured and the impact resistance can be obtained, so it can be effectively used as a blade member.

In addition, if the elastic modulus of the glass fiber is high, the resin-impregnated carbon fiber sheet can be made thinner, thereby reducing costs.

In particular, the outer skin 521 of the blade member 5 is becoming thinner in order to reduce its weight. Therefore, in order to prevent deformation due to its own weight or centrifugal force, a higher elastic modulus is required. Furthermore, this member is usually used outdoors. Therefore, in order to maintain strength against collisions with foreign objects such as birds, it must have high crack resistance (impact resistance). Therefore, the above-mentioned blade member can achieve both strength and impact resistance.

＜6-2. High pressure tank＞ The high-pressure gas tank is used to store high-pressure gases such as compressed hydrogen and compressed natural gas. For example, as shown in FIG. 2 , the high-pressure gas tank is formed into a cylindrical shape and is provided with mouthpieces 63 at both ends in the axial direction. The outer wall of the high-pressure air tank is provided with a lining 61 made of a resin material such as polyamide, and a reinforcing layer 62 is formed inside the lining 61 . The reinforcing layer 62 is formed by laminating a plurality of resin-impregnated fiber sheets. For example, the reinforcing layer 62 may be formed by laminating at least one resin-impregnated glass fiber sheet and at least one resin-impregnated carbon fiber sheet. At this time, the resin-containing carbon fiber sheet is placed inside to ensure the strength against the internal pressure of the groove. On the other hand, the resin-impregnated glass fiber sheet is placed on the outside and can protect the inside of the tank from external impacts on the tank surface. Alternatively, the reinforcing layer 62 may be composed of only resin-impregnated glass fiber sheets.

In particular, when compressed hydrogen is to be stored, it is advantageous to use glass fibers that have excellent low-temperature resistance.

＜6-3. Others＞ In addition to the above-mentioned blade components and high-pressure air tanks, the resin-impregnated glass fiber sheets of the present invention can also be applied to the casings of transport equipment such as helicopters and drones. The resin-impregnated fiberglass sheets are particularly suitable for use in the floor-corresponding portion of the casing.

<7. Characteristics> As described above, the glass fiber of the present invention has a glass skeleton formed of SiO ₂ and therefore can achieve high crack resistance. In addition, since it contains MgO, it can also achieve high elastic modulus and high crack resistance. However, if the MgO content is increased, the SiO ₂ content must be reduced, resulting in a decrease in crack resistance. Therefore, the balance of SiO ₂ and MgO must be adjusted according to the required crack resistance.

For example, if the SiO ₂ content is set to 55% or more and the MgO content is set to 30% or less, glass fibers with high elastic modulus and high crack resistance load can be obtained.

Example Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

Glass fibers with the composition shown in Table 1 were produced, and Young's modulus (volume elastic modulus) and crack resistance load were evaluated. The numerical unit of the composition in Table 1 is mol%. [Table 1]

According to Table 1, if the MgO content increases, the Young's modulus will increase. In addition, when the MgO content increases to a certain level, the crack resistance load will also increase. However, if the SiO content decreases as the _MgO content increases, the crack resistance load will shrink. In particular, if the SiO ₂ content is reduced to less than 55 mol%, the crack resistance load will be significantly reduced. Therefore, in order to achieve high elastic modulus and high crack resistance load, for example, the SiO ₂ content is preferably 55 mol% or more and 62.5 mol% or less, and the MgO content is preferably 22.5 mol% or more and 30 mol% or less. That is, high elasticity and high crack resistance can be achieved through the balance of SiO ₂ content and MgO content.

On the other hand, the comparative example differs from the example in that it does not contain MgO. In terms of physical properties, its Young's modulus and crack resistance load are lower than those of the examples. In particular, its crack resistance load is significantly lower than that of the examples.

5:Paddle components 51:Installation Department 52:Blade body 521:Skin 522: Core material 6:Component 61: lining 62: Reinforcement layer 63: Mouth piece 64:Component

Figure 1 is a cross-sectional view of the blade components. Figure 2 is a cross-sectional view of the high-pressure air tank.

(without)

Claims (9)

A glass fiber containing: SiO ₂ forming a glass skeleton; Al ₂ O ₃ ; and MgO; and the glass fiber has crack resistance. Such as the glass fiber of claim 1, in which the SiO ₂ content is more than 55 mol%. Such as the glass fiber of claim 1 or 2, wherein the aforementioned MgO content is less than 30 mol%. For example, the elastic modulus of the glass fiber in any one of claims 1 to 3 is above 90GPa. The glass fiber according to any one of claims 1 to 4, further containing a rare earth compound. For example, if the glass fiber in any one of the requirements 1 to 5 has a crack resistance load of more than 400g. A fiberglass material formed from the glass fiber of any one of claims 1 to 6, And the glass fiber material is in any form of strands, cut strands, yarns and rovings. A resin-impregnated fiber material with: Glass fiber material, which is formed from the glass fiber in any one of claims 1 to 6, and the glass fiber material is in any form of woven fabric or non-woven fabric; and Resin is infiltrated into the aforementioned glass fiber material. For example, the resin-impregnated fiber material of claim 8 is used as blades of wind turbines for wind power generation, blades of helicopters, blades of drones, or high-pressure tank structures.