CN106126802A - Investigation on Mechanical Properties of Hollow Integrated Sandwich Composites forecast system - Google Patents

Abstract

The present invention relates to a kind of Investigation on Mechanical Properties of Hollow Integrated Sandwich Composites forecast system, single cell model is carefully seen in conjunction with integral hollow interlayer composite material, GUI module based on MATLAB sets up graphic user interface, embed mechanical properties forecast program, pass through yams, thread density, plate thickness, core height, the input variable such as yarn variety and resin types, call function, obtain output variable: integral hollow interlayer composite material under layback (pressure) operating mode through rigidity and the intensity of broadwise, intensity under horizontal drawing (pressure) operating mode, through broadwise unit width bending stiffness and intensity under four-point bending operating mode.The present invention is simple to operate, can forecast every mechanical property of integral hollow interlayer composite material quickly, and forecast precision is high, can effectively shorten the design of material cycle, reduces test period and cost.

Description

Mechanical property forecasting system for integral hollow interlayer composite material

The technical field is as follows:

the invention belongs to the technical field of resin-based composite materials, and particularly relates to a mechanical property forecasting system for an integral hollow interlayer composite material, which is used for forecasting the mechanical property of the integral hollow interlayer composite material under the working conditions of side tension, side compression, horizontal tension, horizontal compression, four-point bending and the like.

Background art:

the integral hollow sandwich composite material is a novel sandwich structure material, has the advantages of light weight, delamination resistance, impact resistance and the like compared with the traditional sandwich material, and has wider application prospect in the fields of high-speed rails, airplanes, ships, floors, partition walls and the like. Therefore, the accurate prediction of the mechanical property has strong practical significance.

At present, the mechanical property of the composite material of the integral hollow interlayer is mainly predicted by establishing a material unit cell model and then obtaining the mechanical property of the material by utilizing finite element simulation (see' Mojtaba Sadighi. Fine element relationship and experimental study on mechanical property behavior of 3D woven glass fiber composite and wire panels [ J ]. Composites Part B,2013,55: 158-. The three-dimensional solid finite element model can describe the microscopic structure and stress distribution of the textile composite material in detail, and has the defects of large modeling workload, long calculation time and inconvenient parameter analysis. And the whole hollow sandwich composite material has a complex structure and many parameters to be considered, so that a prediction tool aiming at the mechanical property of the material is necessary in the design stage of the material structure.

The invention content is as follows:

the invention aims to provide a mechanical property forecasting system for an integral hollow interlayer composite material, which is simple to operate and can forecast various mechanical properties of the integral hollow interlayer composite material with different structural parameters and material components conveniently.

The invention adopts the following technical scheme: a mechanical property forecasting system of an integral hollow interlayer composite material comprises a mechanical property forecasting model and a visual forecasting module; establishing an integral hollow interlayer composite material mesomonas model, and establishing a mechanical property forecasting model in MATLAB by using an analytical method; establishing a graphical user interface based on a GUI module of MATLAB, embedding a program of a mechanical property forecasting model into the graphical user interface, and forecasting the mechanical property of the integral hollow interlayer composite material under various working conditions through function calling to form a visual forecasting system;

the mechanical property forecasting model comprises: on the basis of a mesoscopic unit cell model of the integral hollow interlayer composite material, determining the yarn specification, the yarn density, the panel thickness, the core material height, the yarn type and the resin type as input variables of a mechanical property forecasting system, taking the rigidity and the strength of the warp and weft directions under the side pulling (pressing) working condition, the strength under the horizontal pulling (pressing) working condition and the bending rigidity and the strength of the warp and weft unit width under the four-point bending working condition as output variables, wherein the forecasting model comprises the following steps:

(1) stiffness properties

Calculating the engineering elastic constant of the unidirectional fiber bundle according to the basic mechanical property parameters of the fiber and the resin, obtaining a flexibility matrix of the unidirectional fiber bundle according to the engineering elastic constant of the unidirectional fiber bundle, and further obtaining a rigidity matrix of the unidirectional fiber bundle under a local coordinate system:

C＝S^-1(1)

because the material local coordinate system and the overall coordinate system of most of the yarns in the material are not coincident, the problem of off-axis exists, and the yarns need to be converted into the overall coordinate system through a rotating shaft formula:

C_i＝TCT’ (2)

where T is the transformation matrix and T' is the transpose of T. Obtaining a rigidity matrix of each group of fiber bundles under a general coordinate system by using the formula (2) according to respective directions and inclination angles of the warp fibers, the weft fibers and the pile warps in the integral hollow sandwich composite material;

then according to the geometric structure parameters, integrating the rigidity matrix of each group of fiber bundles according to a volume averaging method to obtain a total rigidity matrix of the unit body:

C_g＝∑λ_iC_i(3)

finally, the total stiffness matrix is inverted to obtain a unit body total flexibility matrix, and further the side pulling (pressing) stiffness of the whole hollow interlayer material is obtained.

The above procedure can be similarly used to calculate if only the stiffness properties of the panel or core portion of the overall hollow sandwich composite are considered.

And calculating the bending rigidity of the integral hollow sandwich composite material on the basis of the required panel rigidity or core material rigidity. According to the geometric structure parameters of the fabric, the proportion of the bending moment borne by the panel in the total bending moment during pure bending is deduced by using the sandwich beam theory, and on the basis, a relation between the macroscopic bending rigidity of the material and the bending rigidity of the panel can be deduced:

$E_{eq}=\frac{(1+\mathrm{\α}\mathrm{\β})E_t{I}_t}{\mathrm{\α}\mathrm{\β}}---\left(4\right)$

wherein E_tFor panel stiffness, I_tPanel moment of inertia, α for panel stiffness to core stiffness ratio, β for panel moment of inertia to core inertia ratio.

(2) Side pull, flat pull and bending strength

And on the basis of the prediction of the rigidity of the material, the strength prediction of the side pulling, the horizontal pulling and the bending of the integral hollow sandwich composite material is carried out according to the embedding strength criterion. The failure mode of the material under the three working conditions is mainly failure of the fiber bundle, wherein the tensile fracture of the fiber bundle is considered under the side-pulling working condition and the horizontal-pulling working condition, the compressive failure of the upper panel is considered under the bending working condition, and the strength can be predicted by adopting a Chua-Wu strength criterion.

And (3) if the stress of the material is sigma under the corresponding working condition, calculating the strain of the material under a general coordinate system by combining the flexibility matrix:

[]_{general of}＝[S]·[σ](5)

And then obtaining the strain of the yarn bundle mainly bearing force under a local coordinate system by using a rotating shaft formula, then solving the stress component of the yarn bundle in the main shaft direction by combining the flexibility matrix of the yarn bundle under the local coordinate system, and finally bringing the obtained stress component into a Cai-Wu strength criterion:

F.I＝F₁σ₁+F₂σ₁+F₁₁σ₁ ²+F₂₂σ₂ ²+F₆₆σ₁₂ ²+2F₁₂σ₁σ₁＝1 (6)

wherein,

$F_1=\frac{1}{X_t}-\frac{1}{X_c},F_2=\frac{1}{Y_t}-\frac{1}{Y_c},F_{11}=\frac{1}{X_t{X}_c},F_{22}=\frac{1}{Y_t{Y}_c},$

$F_{66}=\frac{1}{S^2},F_{12}=\frac{-1}{2\sqrt{X_t{X}_c{Y}_t{Y}_c}},$

X_t、X_c、Y_t、Y_cand S is the longitudinal tensile strength, the longitudinal tensile and compression strength, the transverse tensile strength, the transverse compression strength and the shear strength of the fiber bundle respectively.

And solving the equation (6) to obtain an unknown quantity sigma, namely the strength of the corresponding working condition.

(3) Lateral pressure and flat pressure strength

Different from working conditions of side pulling, horizontal pulling and the like, the failure mode of the material during side pressing is mainly instability of the panel, and the failure mode of the material during horizontal pressing is mainly instability of the core material, so that the strength of the two working conditions can be predicted by adopting a compression bar instability judgment criterion. And embedding a pressure lever instability judgment criterion to predict the lateral pressure and the flat pressure strength on the basis of the panel rigidity and the core material rigidity prediction. The limit load of the pressure lever instability can be solved by adopting an Euler formula, and the breaking strength can be obtained according to the sectional area of the stress surface of the material. The obtained side pressure and flat pressure intensity calculation formulas are as follows:

side pressure strength:

${\mathrm{\σ}}_{cy}=\frac{{\mathrm{F\π}}^2{t}^2}{6L^2}---\left(7\right)$

wherein E is the panel stiffness, t is the panel thickness, and L is the panel height;

flat pressing strength:

${\mathrm{\σ}}_{p1}=\frac{4E_z{\mathrm{\π}}^{2}Ic}{h^2}---\left(8\right)$

wherein E_ZThe rigidity of the core material is shown, I is the inertia moment of the core material, h is the height of the core material, and c is the density of the pile warp.

The construction of the visual forecasting module comprises the following steps: and establishing a graphical user interface based on a GUI module of the MATLAB, embedding a program of a mechanical property forecasting model into the graphical user interface, and forecasting the mechanical properties of the integral hollow interlayer composite material under various working conditions through calling of functions.

The invention has the following beneficial effects:

1. the operation is simple, and various mechanical properties of the integral hollow interlayer composite material can be conveniently and rapidly reported;

2. the forecasting result has higher precision, the test time and cost can be saved, and the design period of the material is shortened;

3. the influence trend of different structural parameters on the mechanical property of the material can be obtained through parameterized calculation, and certain theoretical guidance can be provided for further optimization design of the material.

Description of the drawings:

FIG. 1 is a flow chart of a mechanical property prediction model algorithm.

FIG. 2 is a parameter input interface of the overall hollow sandwich composite material mechanical property forecasting system.

FIG. 3 is a prediction interface of the lateral tension and lateral pressure working conditions of the overall hollow sandwich composite material mechanical property prediction system.

FIG. 4 is a prediction interface of the horizontal pulling and horizontal pressing working conditions of the overall hollow interlayer composite material mechanical property prediction system.

FIG. 5 is a prediction interface of four-point bending condition of the whole hollow interlayer composite material mechanical property prediction system.

The specific implementation mode is as follows:

the mechanical property forecasting system of the integral hollow interlayer composite material comprises a mechanical property forecasting model and a visual forecasting module; establishing an integral hollow interlayer composite material mesomonas model, and establishing a mechanical property forecasting model in MATLAB by using an analytical method; and establishing a graphical user interface based on a GUI module of the MATLAB, embedding a program of a mechanical property forecasting model into the graphical user interface, and forecasting the mechanical property of the integral hollow interlayer composite material under various working conditions by calling a function to form a visual forecasting system.

The mechanical property forecasting model mainly comprises: on the basis of a mesoscopic unit cell model of the integral hollow interlayer composite material, the specification of yarns, the density of the yarns, the thickness of a panel, the height of a core material, the type of the yarns and the type of resin are determined as input variables of a mechanical property forecasting system, and the rigidity and the strength of the warp and weft directions under the side pulling (pressing) working condition, the strength under the horizontal pulling (pressing) working condition and the bending rigidity and the strength of the warp and weft unit width under the four-point bending working condition are determined as output variables. The implementation method of the forecasting model comprises the following steps:

(1) stiffness properties

The rigidity performance of the integral hollow sandwich composite material under different working conditions is calculated according to the flow shown in fig. 1, wherein the specific steps of calculating the lateral pulling (pressing) rigidity are as follows:

calculating the engineering elastic constant of the unidirectional fiber bundle according to the basic mechanical property parameters of the fiber and the resin, obtaining a flexibility matrix of the unidirectional fiber bundle according to the engineering elastic constant of the unidirectional fiber bundle, and further obtaining a rigidity matrix of the unidirectional fiber bundle under a local coordinate system:

C＝S^-1(1)

because the material local coordinate system and the overall coordinate system of most of the yarns in the material are not coincident, the problem of off-axis exists, and the yarns need to be converted into the overall coordinate system through a rotating shaft formula:

C_i＝TCT’ (2)

where T is the transformation matrix and T' is the transpose of T. Obtaining a rigidity matrix of each group of fiber bundles under a general coordinate system by using the formula (2) according to respective directions and inclination angles of the warp fibers, the weft fibers and the pile warps in the integral hollow sandwich composite material;

then according to the geometric structure parameters, integrating the rigidity matrix of each group of fiber bundles according to a volume averaging method to obtain a total rigidity matrix of the unit body:

C_g＝∑λ_iC_i(3)

finally, the total stiffness matrix is inverted to obtain a unit body total flexibility matrix, and further the side pulling (pressing) stiffness of the whole hollow interlayer material is obtained.

The above procedure can be similarly used to calculate if only the stiffness properties of the panel or core portion of the overall hollow sandwich composite are considered.

And calculating the bending rigidity of the integral hollow sandwich composite material on the basis of the required panel rigidity or core material rigidity. According to the geometric structure parameters of the fabric, the proportion of the bending moment borne by the panel in the total bending moment during pure bending is deduced by using the sandwich beam theory, and on the basis, a relation between the macroscopic bending rigidity of the material and the bending rigidity of the panel can be deduced:

$E_{eq}=\frac{(1+\mathrm{\α}\mathrm{\β})E_t{I}_t}{\mathrm{\α}\mathrm{\β}}---\left(4\right)$

wherein E_tFor panel stiffness, I_tPanel moment of inertia, α ratio of panel stiffness to core stiffness, β panel stiffness to core stiffnessThe ratio of the moment of inertia to the core material moment of inertia.

(2) Side pull, flat pull and bending strength

According to the flow shown in fig. 1, based on the above material stiffness prediction, the embedded strength criterion is used to predict the strength of the integral hollow sandwich composite material by side pulling, horizontal pulling and bending. The failure mode of the material under the three working conditions is mainly failure of the fiber bundle, wherein the tensile fracture of the fiber bundle is considered under the side-pulling working condition and the horizontal-pulling working condition, the compressive failure of the upper panel is considered under the bending working condition, and the strength can be predicted by adopting a Chua-Wu strength criterion.

And (3) if the stress of the material is sigma under the corresponding working condition, calculating the strain of the material under a general coordinate system by combining the flexibility matrix:

[]_{general of}＝[S]·[σ](5)

And then obtaining the strain of the yarn bundle mainly bearing force under a local coordinate system by using a rotating shaft formula, then solving the stress component of the yarn bundle in the main shaft direction by combining the flexibility matrix of the yarn bundle under the local coordinate system, and finally bringing the obtained stress component into a Cai-Wu strength criterion:

F.I＝F₁σ₁+F₂σ₁+F₁₁σ₁ ²+F₂₂σ₂ ²+F₆₆σ₁₂ ²+2F₁₂σ₁σ₁＝1 (6)

wherein,

$F_1=\frac{1}{X_t}-\frac{1}{X_c},F_2=\frac{1}{Y_t}-\frac{1}{Y_c},F_{11}=\frac{1}{X_t{X}_c},F_{22}=\frac{1}{Y_t{Y}_c},$

$F_{66}=\frac{1}{S^2},F_{12}=\frac{-1}{2\sqrt{X_t{X}_c{Y}_t{Y}_c}},$

X_t、X_c、Y_t、Y_cs is the longitudinal tensile strength, the longitudinal tensile compression strength, the transverse tensile strength, the transverse compression strength and the shearing strength of the fiber bundle respectivelyAnd (4) degree.

And solving the equation (6) to obtain an unknown quantity sigma, namely the strength of the corresponding working condition.

(3) Lateral pressure and flat pressure strength

Different from working conditions of side pulling, horizontal pulling and the like, the failure mode of the material during side pressing is mainly instability of the panel, and the failure mode of the material during horizontal pressing is mainly instability of the core material, so that the strength of the two working conditions can be predicted by adopting a compression bar instability judgment criterion. According to the flow shown in fig. 1, the side pressure and the flat pressure strength are predicted by embedding the pressure bar buckling criterion on the basis of the panel rigidity and the core material rigidity prediction. The limit load of the pressure lever instability can be solved by adopting an Euler formula, and the breaking strength can be obtained according to the sectional area of the stress surface of the material. The obtained side pressure and flat pressure intensity calculation formulas are as follows:

side pressure strength:

${\mathrm{\σ}}_{cy}=\frac{{\mathrm{E\π}}^2{t}^2}{6L^2}---\left(7\right)$

wherein E is the panel stiffness, t is the panel thickness, and L is the panel height;

flat pressing strength:

${\mathrm{\σ}}_{p1}=\frac{4E_z{\mathrm{\π}}^{2}Ic}{h^2}---\left(8\right)$

wherein E_ZThe rigidity of the core material is shown, I is the inertia moment of the core material, h is the height of the core material, and c is the density of the pile warp.

The construction process of the visual forecasting module comprises the following steps: firstly, establishing a graphical user interface based on a GUI module of MATLAB, then embedding a program of a mechanical property forecasting model into the graphical user interface, and forecasting the mechanical properties of the integral hollow interlayer composite material under various working conditions through calling of functions.

The invention adopts an overall hollow interlayer composite material mechanical property forecasting program written by MATLAB language and GUI module thereof to forecast the performance: inputting the yarn specification, the yarn density, the panel thickness, the core material height, the yarn type and the resin type in the integral hollow interlayer composite material, calculating the corresponding rigidity and strength of the integral hollow interlayer composite material under the working conditions of side tension, side pressure, horizontal tension, horizontal compression, four-point bending and the like by a performance prediction model according to input parameters, and displaying a prediction result through a visual prediction module and simultaneously providing stress diagrams of various working conditions.

The method for predicting the mechanical property of the integral hollow interlayer composite material comprises the following steps:

1. inputting specifications and densities of warp yarns, weft yarns and pile warps on a parameter input interface (shown in figure 2), selecting corresponding fiber and resin types, and inputting the panel thickness and the core material height of the material;

2. clicking a 'calculation' button, entering a parameter pre-output interface (as shown in figures 3-5), and clicking a 'display' button to obtain mechanical property parameters of the material;

3. and selecting a working condition selection button at the upper right corner of the parameter output interface, and switching to different working conditions for checking.

The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.

Claims (1)

1. A system for forecasting the mechanical property of an integral hollow interlayer composite material is characterized in that: the system comprises a mechanical property forecasting model and a visual forecasting module; establishing an integral hollow interlayer composite material mesomonas model, and establishing a mechanical property forecasting model in MATLAB by using an analytical method; establishing a graphical user interface based on a GUI module of MATLAB, embedding a program of a mechanical property forecasting model into the graphical user interface, and forecasting the mechanical property of the integral hollow interlayer composite material under various working conditions through function calling to form a visual forecasting system;

the mechanical property forecasting model comprises: on the basis of a mesoscopic unit cell model of the integral hollow interlayer composite material, determining the yarn specification, the yarn density, the panel thickness, the core material height, the yarn type and the resin type as input variables of a mechanical property forecasting system, taking the rigidity and the strength of the warp and weft directions under the side pulling (pressing) working condition, the strength under the horizontal pulling (pressing) working condition and the bending rigidity and the strength of the warp and weft unit width under the four-point bending working condition as output variables, wherein the forecasting model comprises the following steps:

(1) stiffness properties

Calculating the engineering elastic constant of the unidirectional fiber bundle according to the basic mechanical property parameters of the fiber and the resin, obtaining a flexibility matrix of the unidirectional fiber bundle according to the engineering elastic constant of the unidirectional fiber bundle, and further obtaining a rigidity matrix of the unidirectional fiber bundle under a local coordinate system:

C＝S^-1(1)

because the material local coordinate system and the overall coordinate system of most of the yarns in the material are not coincident, the problem of off-axis exists, and the yarns need to be converted into the overall coordinate system through a rotating shaft formula:

C_i＝TCT’ (2)

wherein T is a conversion matrix, T' is the transposition of T, and the rigidity matrix of each group of fiber bundles under the overall coordinate system is obtained by using the formula (2) according to the respective directions and inclination angles of the warp fibers, the weft fibers and the pile warps in the integral hollow interlayer composite material;

then according to the geometric structure parameters, integrating the rigidity matrix of each group of fiber bundles according to a volume averaging method to obtain a total rigidity matrix of the unit body:

C_g＝∑λ_iC_i(3)

finally, inverting the total stiffness matrix to obtain a unit body total flexibility matrix, and further obtaining the side pulling (pressing) stiffness of the integral hollow interlayer material;

calculating the bending rigidity of the integral hollow sandwich composite material on the basis of the rigidity of the panel or the rigidity of the core material, deducing the proportion of the bending moment borne by the panel in pure bending to the total bending moment by using a sandwich beam theory according to the geometric structure parameters of the fabric, and deducing a relational expression of the macroscopic bending rigidity of the material and the bending rigidity of the panel on the basis:

$E_{eq}=\frac{(1+\mathrm{\α}\mathrm{\β})E_t{I}_t}{\mathrm{\α}\mathrm{\β}}---\left(4\right)$

wherein E_tFor panel stiffness, I_tPanel moment of inertia, α the ratio of panel stiffness to core stiffness, β the ratio of panel moment of inertia to core stiffness;

(2) side pull, flat pull and bending strength

On the basis of the prediction of the rigidity of the material, the strength criterion is embedded to predict the strength of the integral hollow interlayer composite material by side pulling, horizontal pulling and bending, the failure mode of the material under the three working conditions is mainly the failure of the fiber bundle, wherein the tensile fracture of the fiber bundle is considered under the side pulling and horizontal pulling working conditions, the compression failure of the upper panel is considered under the bending working condition, and the strength prediction can be carried out by adopting the Chua-Wu strength criterion;

and (3) if the stress of the material is sigma under the corresponding working condition, calculating the strain of the material under a general coordinate system by combining the flexibility matrix:

[]_{general of}＝[S]·[σ](5)

And then obtaining the strain of the yarn bundle mainly bearing force under a local coordinate system by using a rotating shaft formula, then solving the stress component of the yarn bundle in the main shaft direction by combining the flexibility matrix of the yarn bundle under the local coordinate system, and finally bringing the obtained stress component into a Cai-Wu strength criterion:

wherein,

$F_1=\frac{1}{X_t}-\frac{1}{X_c},F_2=\frac{1}{Y_t}-\frac{1}{Y_c},F_{11}=\frac{1}{X_t{X}_c},F_{22}=\frac{1}{Y_t{Y}_c},$

$F_{66}=\frac{1}{S^2},F_{12}=\frac{-1}{2\sqrt{X_t{X}_c{Y}_t{Y}_c}},$

X_t、X_c、Y_t、Y_cs is respectively the longitudinal tensile strength, the longitudinal tensile compression strength, the transverse tensile strength, the transverse compression strength and the shear strength of the fiber bundle, and an unknown quantity sigma is obtained by solving an equation (6), namely the strength of the corresponding working condition;

(3) lateral pressure and flat pressure strength

Different from working conditions such as side pulling and horizontal pulling, the failure mode of the material during side pressure is mainly the instability of a panel, the failure mode of the material during horizontal pressing is mainly the instability of a core material, therefore, the strength of the two working conditions can be predicted by adopting a compression bar instability judgment criterion, the compression bar instability judgment criterion is embedded to predict the side pressure and the horizontal pressure strength on the basis of the prediction of the panel rigidity and the core material rigidity, the limit load of the compression bar instability can be solved by adopting an Euler formula, the failure strength can be obtained according to the sectional area of a material stress surface, and the calculation formulas of the obtained side pressure and the horizontal pressure strength are as follows:

side pressure strength:

${\mathrm{\σ}}_{cy}=\frac{{\mathrm{E\π}}^2{t}^2}{6L^2}---\left(7\right)$

wherein E is the panel stiffness, t is the panel thickness, and L is the panel height;

flat pressing strength:

${\mathrm{\σ}}_{pl}=\frac{4E_z{\mathrm{\π}}^{2}Ic}{h^2}---\left(8\right)$

wherein E_ZThe rigidity of the core material is shown, I is the inertia moment of the core material, h is the height of the core material, and c is the density of the pile warp;

the construction of the visual forecasting module comprises the following steps: and establishing a graphical user interface based on a GUI module of the MATLAB, embedding a program of a mechanical property forecasting model into the graphical user interface, and forecasting the mechanical properties of the integral hollow interlayer composite material under various working conditions through calling of functions.