CN104730211A - Method for measuring fiber volume content of composite material - Google Patents

Abstract

The invention provides a method for testing the volume fraction of a composite material, which indirectly obtains the volume content of each component of the composite material through the mass content of each component of the composite material, and is suitable for single reinforcement composite materials and multiple reinforcement composite materials, The operation is convenient, and it provides a way for the determination of the fiber volume content of various fiber hybrid composite materials, and also provides a convenience for the actual production process of composite materials to calculate the fiber volume content through the ratio of each component for structural force analysis.

Description

A test method for fiber volume content of composite materials

technical field

The invention relates to a method for testing the volume fraction of a composite material, and the composite material includes a single reinforcement composite material, two or more reinforcement composite materials.

Background technique

The fiber volume content of composite materials is an important basis for mechanical analysis, evaluation, calculation and design of composite materials, and its size affects the performance of composite materials in all aspects. At present, the methods for measuring fiber volume content mainly include (metallographic) microscopy, computer image processing, resin dissolution method, and conductivity method. Since glass fiber reinforced composite materials are almost transparent, some resins are also difficult to dissolve or have a long dissolution period. The method is difficult to apply to glass fiber reinforced composite materials; in addition, there are density method and calcination method, which are also difficult to realize for carbon fiber reinforced composite materials, and it is even more difficult to find a suitable method to measure the volume content of fibers for carbon/glass hybrid composite materials.

In practical engineering applications, the mass ratio of fibers and matrix is generally controlled, while in the structural design and mechanical performance analysis of composite materials, the volume content of fibers is often used to calculate, in order to measure and control the ratio in practical applications For convenience and theoretical analysis and calculation of mechanical properties, a method for determining the volume content by testing the fiber mass content is needed.

Contents of the invention

The purpose of the present invention is to provide a method for determining the fiber volume content through the fiber mass content, so as to solve the difficulty in determining the fiber volume content of composite materials such as carbon/glass hybrid composite materials.

In order to achieve the above object, the technical solution of the present invention provides a method for testing the fiber volume content of a composite material, the composite material contains N kinds of fibers, N≥1, characterized in that the steps are:

The first step is to obtain the density of each fiber in the N types of fibers, wherein the density of the i-th fiber is ρ _i , i=1,...,N;

The second step is to take the pure resin matrix and cure it under the same curing process conditions as the above-mentioned N kinds of fibers and their reinforcements after degassing, and then measure the density ρ _c of the resin matrix after curing;

The third step is to obtain the amount of various fibers in the composite material, wherein the amount of the i-th fiber is m _i ;

The fourth step is to take the above-mentioned N kinds of fibers and vacuum infuse them with the resin matrix after degassing according to the design requirements, and calculate the amount of resin used as m _c , the amount of each fiber is the same as the measurement unit of the amount of resin, or Calculate the mass fraction of various fibers and resins, wherein the mass fraction of the i-th fiber is W _i , and the mass fraction of the resin is W _c ;

The fifth step is to calculate the volume content V _c of the resin, $V_c=\frac{\frac{m_c}{{\mathrm{\ρ}}_c}}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{m_i}{{\mathrm{\ρ}}_i}+\frac{m_c}{{\mathrm{\ρ}}_c}}$ or $V_c=\frac{\frac{W_c}{{\mathrm{\ρ}}_c}}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{W_i}{{\mathrm{\ρ}}_i}+\frac{W_c}{{\mathrm{\ρ}}_c}};$ Calculate the volume content of various fibers, wherein the density of the jth fiber is V _j , j=1,...,N, $V_j=\frac{\frac{m_j}{{\mathrm{\ρ}}_j}}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{m_i}{{\mathrm{\ρ}}_i}+\frac{m_c}{{\mathrm{\ρ}}_c}}$ or $V_j=\frac{\frac{W_j}{{\mathrm{\ρ}}_j}}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{W_i}{{\mathrm{\ρ}}_i}+\frac{W_c}{{\mathrm{\ρ}}_c}}.$

The present invention provides a method for indirect calculation of volume content by mass or mass fraction, and provides a method for composite materials, especially hybrid composite materials whose volume fraction is difficult to measure by traditional methods. This method is easy to operate and practical. The density of fiber and resin can be directly obtained, and it is also in line with the actual process to control the distribution ratio of each component by mass means. Only by obtaining the mass of each component in the composite material can the fiber volume fraction be obtained, which can be used for analysis and calculation and evaluation etc.

Detailed ways

In order to make the present invention more comprehensible, preferred embodiments are described in detail as follows.

In this embodiment, the carbon/glass fiber unidirectional cloth interlayer hybrid reinforced epoxy resin composite material is taken as an example to further illustrate the present invention.

The test method for the fiber volume content of the carbon/glass fiber unidirectional cloth layer hybrid reinforced epoxy resin composite material disclosed in this embodiment is characterized in that the steps are:

The first step is to obtain the carbon fiber density ρ _C and the glass fiber density ρ _G .

The second step is to take an appropriate amount of epoxy resin, defoam it and cure it under the same curing process conditions as the carbon/glass interlayer hybrid fiber preform and its reinforcement, and measure the density ρ _H of the cured resin.

The third step is to cut and weigh unidirectional carbon fiber cloth and unidirectional glass fiber cloth of a certain size (such as 50*50cm) several times, and calculate the average surface weight of unidirectional carbon fiber cloth and unidirectional glass fiber cloth. Pay attention to the shape retention of the fabric.

The fourth step is to cut the unidirectional carbon fiber cloth and unidirectional glass fiber cloth of a certain size required by the composite material to make a hybrid fiber preform according to the design layup requirements, and vacuum infuse it with an appropriate amount of degassed epoxy resin. Plate M.

The fifth step, in order to exclude the influence of the surrounding resin enrichment area, take a certain size in the center of the plate M and cut it into a cuboid or cube N, measure the size of the cuboid or cube N and calculate the area as S.

The sixth step is to calculate the weight of unidirectional carbon fiber cloth and unidirectional glass fiber cloth contained in the plate from the surface weight of unidirectional carbon fiber cloth and unidirectional glass fiber cloth, the number of layers required for each cloth, and the area S of a cuboid or cube N They are m _C , m _{G ,} respectively.

Step 7. Place the cuboid or cube N under standard temperature and humidity conditions for 24 hours and then weigh it. Combine m _C and m _G to calculate the weight of the matrix as m _H . At the same time, the mass fractions of carbon fiber, glass fiber and matrix can be calculated. are W _C , W _G , W _H .

The eighth step, calculate the volume content V _H of the resin, or $V_h=\frac{\frac{W_h}{{\mathrm{\ρ}}_h}}{\frac{W_C}{{\mathrm{\ρ}}_C}+\frac{W_G}{{\mathrm{\ρ}}_G}+\frac{W_h}{{\mathrm{\ρ}}_h}};$

Calculate the volume content V _C of carbon fibers, $V_C=\frac{\frac{m_C}{{\mathrm{\ρ}}_C}}{\frac{m_C}{{\mathrm{\ρ}}_C}+\frac{m_G}{{\mathrm{\ρ}}_G}+\frac{m_h}{{\mathrm{\ρ}}_h}}$ or $V_C=\frac{\frac{W_C}{{\mathrm{\ρ}}_C}}{\frac{W_C}{{\mathrm{\ρ}}_C}+\frac{W_G}{{\mathrm{\ρ}}_G}+\frac{W_h}{{\mathrm{\ρ}}_h}};$

Calculate the volume content V _G of glass fibers, $V_G=\frac{\frac{m_G}{{\mathrm{\ρ}}_G}}{\frac{m_C}{{\mathrm{\ρ}}_C}+\frac{m_G}{{\mathrm{\ρ}}_G}+\frac{m_h}{{\mathrm{\ρ}}_h}}$ or $V_G=\frac{\frac{W_G}{{\mathrm{\ρ}}_G}}{\frac{W_C}{{\mathrm{\ρ}}_C}+\frac{W_G}{{\mathrm{\ρ}}_G}+\frac{W_h}{{\mathrm{\ρ}}_h}}.$

If it is a single enhancer, m _C (W _C )=0 or m _G (W _G )=0 can be set.

Claims (1)

1. a method of testing for composites fiber volume fraction, this compound substance contains N kind fiber, and N >=1, is characterized in that, step is:

The density of often kind of fiber in the first step, acquisition N kind fiber, wherein, the density of i-th kind of fiber is ρ _i, i=1 ..., N;

Second step, get pure resin matrix deaeration after above-mentioned N kind fiber and its reinforced foam plastics with curing process condition under solidify, measure the density p of resin matrix after solidification subsequently _c;

The consumption of various fiber in 3rd step, acquisition compound substance, wherein, the consumption of i-th kind of fiber is m _i;

4th step, get above-mentioned N kind fiber according to the resin matrix vacuum infusion molding after the requirement of design and deaeration, and the consumption calculating resin used is m _c, the consumption of various fiber is identical with the measurement unit of the consumption of resin, or calculates the massfraction of various fiber and resin, and wherein, the massfraction of i-th kind of fiber is W _i, the massfraction of resin is W _c;

5th step, calculate the volume content V of resin _c, or

Calculate the volume content of various fiber, wherein, the density of jth kind fiber is V _j, j=1 ..., N, $V_j=\frac{\frac{m_j}{{\mathrm{\ρ}}_j}}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{m_i}{{\mathrm{\ρ}}_i}+\frac{m_c}{{\mathrm{\ρ}}_c}}$ Or $V_j=\frac{\frac{W_j}{{\mathrm{\ρ}}_j}}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{W_i}{{\mathrm{\ρ}}_i}+\frac{W_c}{{\mathrm{\ρ}}_c}}.$ 。