Method for detecting room-temperature bending strength of continuous fiber reinforced ceramic matrix composite
Technical Field
The invention relates to the technical field of detection of ceramic mechanics, in particular to a method for detecting room-temperature bending strength of a continuous fiber reinforced ceramic-based composite material.
Background
At present, various testing methods and standards are provided for the room-temperature bending strength of the continuous fiber reinforced ceramic matrix composite, data obtained according to different standards have differences, the fiber reinforced ceramic matrix composite is a porous ceramic material, obvious defects such as holes and cracks cannot be avoided in the sample processing and preparation process, if the requirements of standard sizes are strictly met, the phenomenon that a defective test sample cannot be used as an unqualified piece is avoided, the cost is increased, and the test period is prolonged. Based on the above, a new size for the fiber reinforced ceramic-based material needs to be designed, so that even if the sample has defects in the width or thickness direction, the sample can be processed again on the basis of meeting the width-thickness ratio, and the use value of the test piece is improved.
Because the stress direction of the sample in the bending method test is the pressure in the vertical direction, on the premise of ensuring the span distance, the sample is too thin, and on the one hand, the measurement size is easy to cause larger deviation, so that the numerical calculation has larger error; on the other hand, the ceramic material is high in brittleness, the thinner the ceramic material is, the residual stress and the defect generation probability are increased, the residual stress and the defect generation probability are all unfavorable for the test result, when the thickness is larger than or equal to 4mm, the radial bending of the 2.5D fiber reinforced ceramic-based material is 120MPa, the latitudinal bending is 78MPa, when the thickness is 1.2mm, the radial bending of the fiber reinforced ceramic-based material with the same structure is reduced to 63MPa, the latitudinal bending is 40MPa, and the attenuation is nearly half. And the different sampling directions of the continuous fiber reinforced ceramic materials with different structures can cause larger deviation of the test result.
These phenomena have disadvantages in accurately characterizing the properties of the material, and thus are liable to bring quality risks to the product, and need to be improved.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for detecting the room-temperature bending strength of a continuous fiber reinforced ceramic matrix composite.
According to one aspect of the present invention, there is provided a method for testing the room-temperature bending strength of a continuous fiber reinforced ceramic matrix composite, comprising the steps of:
determining the structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the obtained sample according to the weaving direction of the fiber reinforcements of the continuous fiber reinforced ceramic matrix composite, and cutting and processing the continuous fiber reinforced ceramic matrix composite to obtain the sample, wherein the width-to-thickness ratio of the sample is (2.3-2.6):1, and the thickness is more than or equal to 4 mm;
clamping the test sample on a clamp of a testing machine;
and loading the sample, and collecting detection data for data processing to obtain corresponding bending strength data of the continuous fiber reinforced ceramic matrix composite.
The fiber reinforced ceramic-based material is a porous ceramic material, obvious defects such as holes and cracks can not be avoided in the sample processing and preparation process, if the standard size requirement is strictly met, the phenomenon that a defective test sample cannot be used as a defective test sample exists, the cost is increased, and the test period is prolonged. Based on the design, the invention designs a new size, even if the sample has defects in the width or thickness direction, the sample can be processed again on the basis of meeting the width-thickness ratio, and the use value of the test piece is improved.
Because the stress direction of the sample in the bending method test is the pressure in the vertical direction, on the premise of ensuring the span distance, the sample is too thin, and on the one hand, the measurement size is easy to cause larger deviation, so that the numerical calculation has larger error; on the other hand, the ceramic material is high in brittleness, the thinner the ceramic material is, the residual stress and the defect generation probability are increased, the residual stress and the defect generation probability are all unfavorable for the test result, when the thickness is larger than or equal to 4mm, the radial bending of the 2.5D fiber reinforced ceramic-based material is 120MPa, the latitudinal bending is 78MPa, when the thickness is smaller than 4mm, the corresponding performance begins to attenuate, when the thickness is 1.2mm, the radial bending of the fiber reinforced ceramic-based material with the same structure is reduced to 63MPa, the latitudinal bending is 40MPa, and the attenuation is nearly half. The excessive thickness of the test sample can cause the waste of the composite material, further increase the test cost, and invisibly increase the processing difficulty and workload, and most importantly, along with the increase of the size of the fiber reinforced ceramic matrix composite material, the probability of the occurrence of more obvious defects such as holes, cracks and the like is increased, the probability of the test sample becoming an unqualified piece is increased, the probability of the error of the test result is increased, the size of the test sample obtained through a large number of experiments can not only ensure the accuracy of the material test, but also be processed conveniently, and the cost can be effectively saved.
The structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the sample can effectively keep the effective units of the sample, ensure the similarity between the detected value and the actual value, and further obtain the material performance of the composite material.
The test methods for the test specimens include a three-point bending method or a four-point bending method.
When the test method of the test specimen is a three-point bending method, the dimensions of the test specimen include standard dimensions or special dimensions,
wherein,
the standard size of the sample was 120 (+ -1) mm × 11 (+ -0.2) mm × 4.5 (+ -0.2) mm;
the special size is that the length of the sample is plus 22 (+ -0.2) mm, the thickness is more than or equal to 4mm, and the external span/sample thickness is more than or equal to 20.
When the test specimen testing method is a four-point bending method, the test specimen dimensions include standard dimensions or special dimensions,
wherein,
the standard size of the sample is 170 (+ -1) mm × 11 (+ -0.2) mm × 4.5 (+ -0.2) mm;
the special size is that the length of the sample is plus 22 (+ -0.2) mm, the thickness is more than or equal to 4mm, (outer span-inner span)/the thickness of the sample is more than or equal to 20, and the inner span is outer span/3.2 +/-0.1.
When the composite material is reinforced two-dimensionally by the fiber reinforcement, the sample has 3 or more layers of the fiber reinforcement in the thickness direction and 3 or more fiber bundles in the width direction.
When the fiber reinforcement three-dimensionally reinforces the composite material, the fiber reinforcement of the sample in the thickness direction comprises 1 or more structural units of fiber bundle unit fabric; the fiber reinforcement in the width direction includes 1 or more structural units of a fiber bundle unit weave.
The construction unit requires the sample to have a complete fiber bundle unit in the thickness or width direction.
The structure and/or quantity of the fiber reinforcement bodies in the thickness direction and the width direction of the sample are obtained on the basis of analyzing the appearance, the microcosmic data and the mass data of the material for many times. The given data can truly reflect the effective unit and material performance to the maximum extent. When the value is lower than the above value, the fiber is seriously damaged in the processing process, and the test value is reduced by about 30% compared with the test value, so that the material performance cannot be correctly evaluated.
The size measurement was accurate to 0.02 mm.
The loading speed is set to 0.4-0.6 mm/min.
The recording occurred after the maximum load occurred and continued to be applied to load values below 50% of the maximum.
When the phenomena of damage outside the maximum bending moment of the sample, obvious parallel cracks in the width direction of the sample, interlaminar damage, outer support roller fracture and the like occur, the sample is judged to be improper, and a new sample needs to be added.
Compared with the prior art, the invention has the following beneficial effects:
the method for detecting the room-temperature bending strength of the continuous fiber reinforced ceramic matrix composite material determines the structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the obtained sample according to the weaving direction of the fiber reinforcements of the continuous fiber reinforced ceramic matrix composite material, cuts and processes the continuous fiber reinforced ceramic matrix composite material to obtain the sample, wherein the width-thickness ratio of the sample is (2.3-2.6):1, and the thickness is not less than 4mm, the structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the sample can effectively keep the effective units of the sample, ensure the similarity between the detected value and the true value, further faithfully obtain the material performance of the composite material, and the size of the sample is selected to ensure that the sample can be processed again on the basis of meeting the width-thickness ratio even if the sample has defects in the width direction or the thickness direction, the use value of a test piece is improved, because the stress direction of a test sample in a bending method test is the pressure in the vertical direction, the size of the test piece can avoid the problems that the test sample is too thin and causes larger deviation easily when measuring the size and increases the generation chance of residual stress and defects on the premise of ensuring the span, and can also avoid the problem that the test sample is too thick and can cause the waste of the composite material, so the test cost is increased, the processing difficulty and the workload are increased invisibly, most importantly, along with the increase of the size of the fiber reinforced ceramic matrix composite material, the probability of the obvious defects such as holes, cracks and the like is increased, the probability of the test sample becoming a disqualified piece is increased, the probability of the error of the test result is increased, and then the test sample is clamped on a clamp of a test machine; and loading the sample, and collecting detection data for data processing to obtain corresponding bending strength data of the continuous fiber reinforced ceramic matrix composite. The whole method is scientific, reasonable, simple, feasible, quick and effective, has low cost and is worthy of popularization.
Detailed Description
In order to better understand the technical solution of the present invention, the following embodiments are provided to further explain the present invention.
The first embodiment is as follows:
the embodiment provides a method for detecting the room-temperature bending strength of a continuous fiber reinforced ceramic matrix composite, which comprises the following steps of:
s1, determining the structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the obtained sample according to the weaving direction of the fiber reinforcements of the continuous fiber reinforced ceramic matrix composite, cutting and processing the continuous fiber reinforced ceramic matrix composite to obtain the sample, wherein the size of the sample is a standard size,
the standard dimensions of the test specimen are 120mm by 11mm by 4.5mm in length by width by thickness.
The test method of the sample is a three-point bending method, and the material of the sample is specifically quartz fiber reinforced ceramic composite material with a three-dimensional structure.
And during the size measurement, a vernier caliper with the precision of 0.02mm is selected and used, and the precision is 0.02 mm.
Fiber reinforcement when the said composite material of three-dimensional reinforcement, the sample includes 1 fiber bundle unit structural unit of the unit fabric in the direction of thickness fiber reinforcement; the fiber reinforcement in the width direction comprises 1 fiber bundle unit fabric construction unit; the thickness deviation is less than or equal to +/-5 percent of the average value.
And S2, clamping the test sample on a clamp of a testing machine.
And S3, loading the sample, and collecting detection data for data processing to obtain corresponding bending strength data of the continuous fiber reinforced ceramic matrix composite.
The loading speed was set to 0.4 mm/min.
Continuing loading until the loading load value is lower than 50% of the maximum load after the loading load in a display connected with the testing machine reaches the peak value, stopping loading and recording;
when the phenomena of damage outside the maximum bending moment of the sample, obvious parallel cracks in the width direction of the sample, interlaminar damage, outer support roller fracture and the like occur, the sample is judged to be improper, and a new sample needs to be added; not the above phenomenon, recording is available.
Three-point bending strength pressThe calculation is carried out according to the calculation,
wherein,
σf.mthe bending strength (MPa) is given,
Fmin order to be the load (N),
l is the span (mm),
b is the width (mm) of the specimen,
h is the specimen thickness (mm).
Each bending strength data i.e. bending strength performance test results is an average of the corresponding bending strength valid test results,
mean value is according toThe calculation is carried out according to the calculation,
standard deviation according toThe calculation is carried out according to the calculation,
wherein, XiFor the test results, n is the number of valid tests.
Example two:
the embodiment provides a method for detecting the room-temperature bending strength of a continuous fiber reinforced ceramic matrix composite, which comprises the following steps of:
the embodiment provides a method for detecting the room-temperature bending strength of a continuous fiber reinforced ceramic matrix composite, which comprises the following steps of:
s1, determining the structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the obtained sample according to the weaving direction of the fiber reinforcements of the continuous fiber reinforced ceramic matrix composite, cutting and processing the continuous fiber reinforced ceramic matrix composite to obtain the sample, wherein the size of the sample is a standard size,
the test method of the test specimen is a four-point bending method,
the standard size of the test specimen is 170mm by 11mm by 4.5mm in length by width by thickness.
The material of the sample is specifically quartz fiber reinforced ceramic composite material with a two-dimensional structure.
And during the size measurement, a vernier caliper with the precision of 0.02mm is selected and used, and the precision is 0.02 mm.
When the fiber reinforcement two-dimensionally reinforces the composite material, the fiber reinforcement of the sample is 4 layers in the thickness direction, the fiber reinforcement comprises 5 fiber bundles in the width direction, and the thickness deviation is less than or equal to +/-5 percent of the average value.
And S2, clamping the test sample on a clamp of a testing machine.
And S3, loading the sample, and collecting detection data for data processing to obtain corresponding bending strength data of the continuous fiber reinforced ceramic matrix composite.
The loading speed was set to 0.6 mm/min.
Continuing loading until the loading load value is lower than 50% of the maximum load after the loading load in a display connected with the testing machine reaches the peak value, stopping loading and recording;
when the phenomena of damage outside the maximum bending moment of the sample, obvious parallel cracks in the width direction of the sample, interlaminar damage, outer support roller fracture and the like occur, the sample is judged to be improper, and a new sample needs to be added; not the above phenomenon, recording is available.
Four-point bending strength according toThe calculation is carried out according to the calculation,
wherein,
σf.mthe bending strength (MPa) is given,
Fmin order to be the load (N),
l is the outer span (mm),
Liis an inner span (mm),
b is the width (mm) of the specimen,
h is the specimen thickness (mm).
Each bending strength data i.e. bending strength performance test results is an average of the corresponding bending strength valid test results,
mean value is according toThe calculation is carried out according to the calculation,
standard deviation according toThe calculation is carried out according to the calculation,
wherein, XiFor the test results, n is the number of valid tests.
Example three:
the embodiment provides a method for detecting the room-temperature bending strength of a continuous fiber reinforced ceramic matrix composite, which comprises the following steps of:
s1, determining the structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the obtained sample according to the weaving direction of the fiber reinforcements of the continuous fiber reinforced ceramic matrix composite, cutting and processing the continuous fiber reinforced ceramic matrix composite to obtain the sample, wherein the size of the sample is a special size,
the test method of the sample is a three-point bending method,
the special size is that the length of the sample is +22mm, the thickness is more than or equal to 4mm, and the outer span/sample thickness is more than or equal to 20.
And during the size measurement, a vernier caliper with the precision of 0.02mm is selected and used, and the precision is 0.02 mm.
When the fiber reinforcement two-dimensionally reinforces the composite material, the fiber reinforcement of the sample is 3 layers in the thickness direction, the fiber reinforcement comprises 3 fiber bundles in the width direction, and the thickness deviation is less than or equal to +/-5 percent of the average value.
And S2, clamping the test sample on a clamp of a testing machine.
And S3, loading the sample, and collecting detection data for data processing to obtain corresponding bending strength data of the continuous fiber reinforced ceramic matrix composite.
The loading speed is set to 0.4-0.6 mm/min.
Continuing loading until the loading load value is lower than 50% of the maximum load after the loading load in a display connected with the testing machine reaches the peak value, stopping loading and recording;
when the phenomena of damage outside the maximum bending moment of the sample, obvious parallel cracks in the width direction of the sample, interlaminar damage, outer support roller fracture and the like occur, the sample is judged to be improper, and a new sample needs to be added; not the above phenomenon, recording is available.
Three-point bending strength pressThe calculation is carried out according to the calculation,
wherein,
σf.mthe bending strength (MPa) is given,
Fmin order to be the load (N),
l is the span (mm),
b is the width (mm) of the specimen,
h is the specimen thickness (mm).
Each bending strength data i.e. bending strength performance test results is an average of the corresponding bending strength valid test results,
mean value is according toThe calculation is carried out according to the calculation,
standard deviation according toThe calculation is carried out according to the calculation,
wherein, XiFor the test results, n is the number of valid tests.
Example four:
the same features of this embodiment and the third embodiment are not repeated, and the different features of this embodiment and the third embodiment are:
the special size is that the length of the sample is +22.2mm, the thickness is more than or equal to 4mm, and the outer span/sample thickness is more than or equal to 20.
The fiber reinforcement three-dimensionally strengthens the composite material, and the fiber reinforcement of the sample in the thickness direction comprises 2 construction units of fiber bundle unit fabric; the fiber reinforcement in the width direction comprises 3 construction units of a fiber bundle unit fabric. The thickness deviation is less than or equal to +/-5 percent of the average value.
The loading speed was set to 0.4 mm/min.
Example five:
the same features of this embodiment and the third embodiment are not repeated, and the different features of this embodiment and the third embodiment are:
the special size is that the length of the sample is plus 21.8mm, the thickness is more than or equal to 4mm, and the outer span/sample thickness is more than or equal to 20.
The fiber reinforcement three-dimensionally reinforces the composite material, and the fiber reinforcement of the sample in the thickness direction comprises 1 construction unit of fiber bundle unit fabric; the fiber reinforcement in the width direction comprises 1 structural unit of a fiber bundle unit fabric. The thickness deviation is less than or equal to +/-5 percent of the average value.
The loading speed was set to 0.5 mm/min.
Example six:
the same features of this embodiment and the third embodiment are not repeated, and the different features of this embodiment and the third embodiment are:
when the fiber reinforcement two-dimensionally reinforces the composite material, the fiber reinforcement of the sample is 4 layers in the thickness direction, the fiber reinforcement comprises 4 fiber bundles in the width direction, and the thickness deviation is less than or equal to +/-5 percent of the average value.
Example seven:
the embodiment provides a method for detecting the room-temperature bending strength of a continuous fiber reinforced ceramic matrix composite, which comprises the following steps of:
s1, determining the structure and/or the number of the fiber reinforcements in the thickness direction and the width direction of the obtained sample according to the weaving direction of the fiber reinforcements of the continuous fiber reinforced ceramic matrix composite, cutting and processing the continuous fiber reinforced ceramic matrix composite to obtain the sample, wherein the size of the sample is a special size,
the test method of the test specimen is a four-point bending method,
the special size is that the length of the sample is span +22mm, the thickness is more than or equal to 4mm, (outer span-inner span)/the thickness of the sample is more than or equal to 20, and the inner span is outer span/3.2.
And during the size measurement, a vernier caliper with the precision of 0.02mm is selected and used, and the precision is 0.02 mm.
Fiber reinforcement when the composite material was reinforced two-dimensionally, the sample had 4 layers of fiber reinforcement in the thickness direction and 4 fiber bundles in the width direction.
And S2, clamping the test sample on a clamp of a testing machine.
And S3, loading the sample, and collecting detection data for data processing to obtain corresponding bending strength data of the continuous fiber reinforced ceramic matrix composite.
The loading speed was set to 0.5 mm/min.
Continuing loading until the loading load value is lower than 50% of the maximum load after the loading load in a display connected with the testing machine reaches the peak value, stopping loading and recording;
when the phenomena of damage outside the maximum bending moment of the sample, obvious parallel cracks in the width direction of the sample, interlaminar damage, outer support roller fracture and the like occur, the sample is judged to be improper, and a new sample needs to be added; not the above phenomenon, recording is available.
Four-point bending strength according toThe calculation is carried out according to the calculation,
wherein,
σf.mthe bending strength (MPa) is given,
fm is the load (N),
l is the outer span (mm),
Liis an inner span (mm),
b is the width (mm) of the specimen,
h is the specimen thickness (mm).
Each bending strength data i.e. bending strength performance test results is an average of the corresponding bending strength valid test results,
mean value is according toThe calculation is carried out according to the calculation,
standard deviation according toThe calculation is carried out according to the calculation,
wherein, XiFor the test results, n is the number of valid tests.
Example eight:
the features of this embodiment that are the same as those of the seventh embodiment are not described again, and the features of this embodiment that are different from those of the seventh embodiment are:
the special size is that the length of the sample is span +22.2mm, the thickness is more than or equal to 4mm, (outer span-inner span)/the thickness of the sample is more than or equal to 20, and the inner span is outer span/3.2 + 0.1.
And during the size measurement, a vernier caliper with the precision of 0.02mm is selected and used, and the precision is 0.02 mm.
When the fiber reinforcement two-dimensionally reinforces the composite material, the fiber reinforcement of the sample is 5 layers in the thickness direction, the fiber reinforcement comprises 5 fiber bundles in the width direction, and the thickness deviation is less than or equal to +/-5 percent of the average value.
The loading speed was set to 0.5 mm/min.
Example nine:
the features of this embodiment that are the same as those of the seventh embodiment are not described again, and the features of this embodiment that are different from those of the seventh embodiment are:
the special size is that the length of the sample is span +21.8mm, the thickness is more than or equal to 4mm, (outer span-inner span)/the thickness of the sample is more than or equal to 20, and the inner span is outer span/3.2-0.1.
The fiber reinforcement two-dimensionally reinforces the composite material, the fiber reinforcement of the sample is 3 layers in the thickness direction, the fiber reinforcement comprises 3 fiber bundles in the width direction, and the thickness deviation is less than or equal to +/-5 percent of the average value.
The loading speed was set to 0.6 mm/min.
Example ten:
the same features of this embodiment and the first embodiment are not described again, and the different features of this embodiment and the first embodiment are:
the standard dimensions of the test specimens were 121 mm. times.11.2 mm. times.4.7 mm.
Fiber reinforcement when three-dimensionally reinforcing the composite material, the sample contains 3 fiber bundle unit fabric construction units in the thickness direction; a construction unit comprising 3 fiber bundle unit fabrics in the width direction of the fiber reinforcement; the thickness deviation is less than or equal to +/-5 percent of the average value.
The loading speed was set to 0.6 mm/min.
Example eleven:
the same features of this embodiment and the first embodiment are not described again, and the different features of this embodiment and the first embodiment are:
the standard dimensions of the test specimens were 119mm by 10.8mm by 4.3 mm.
Fiber reinforcement when three-dimensionally reinforcing the composite material, the sample contains 2 fiber bundle unit fabric construction units in the thickness direction; the fiber reinforcement in the width direction comprises a construction unit of 2 fiber bundle unit fabrics; the thickness deviation is less than or equal to +/-5 percent of the average value.
The loading speed was set to 0.5 mm/min.
Example twelve:
the features of this embodiment that are the same as those of the second embodiment are not described again, and the features of this embodiment that are different from those of the second embodiment are:
the standard dimensions of the test specimens were 171 mm. times.11.2 mm. times.4.7 mm.
Fiber reinforcement when the composite was reinforced two-dimensionally, the sample had 5 layers of fiber reinforcement in the thickness direction and 6 fiber bundles in the width direction.
The loading speed was set to 0.5 mm/min.
Example thirteen:
the features of this embodiment that are the same as those of the second embodiment are not described again, and the features of this embodiment that are different from those of the second embodiment are:
the standard dimensions of the test specimens were 169mm by 10.8mm by 4.3 mm.
Fiber reinforcement when the composite material was reinforced two-dimensionally, the sample had 3 layers of fiber reinforcement in the thickness direction and 3 fiber bundles in the width direction.
The loading speed was set to 0.4 mm/min.
Example fourteen:
the same features of this embodiment and the first embodiment are not described again, and the different features of this embodiment and the first embodiment are:
the standard dimensions of the test specimen are 120mm by 11 (+ -0.2) mm by 4.5 (+ -0.2) mm in length by width by thickness.
The loading speed was set to 0.5 mm/min.
Example fifteen:
taking a quartz fiber reinforced fused silica ceramic composite material (abbreviated as quartz fiber reinforced sample in table 1) as an example, the room temperature bending property was measured in the manner of the fourteenth embodiment, and the obtained data is shown in table 1:
table 1: flexural strength performance data of quartz fiber reinforced fused quartz ceramic composite material
As can be seen from Table 1, for 5 samples of one material, the obtained bending strength data has very small difference and high test accuracy, which cannot be achieved by the existing detection method.
Wherein the test machine is specifically an electronic universal material testing machine, and the model is: AG-IC100 KN.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the specific combination of features described above, but also covers other embodiments where any combination of the features described above or their equivalents is used without departing from the inventive concept described above. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.