CN1528586A - Filament winding composite material pressure vessel gradient tension construction method - Google Patents

Abstract

The invention discloses a method to exert gradient tension on fiber-winded composite pressure container, its winding layer is winded from inside to outside in a gradient winding-tension descending mode, where it can accurately calculate the gradient tension of winding fiber according to formula and control the winding tension through the tension control system, which makes all the fiber layers of the pressure container have the same initial stress, so as to heathen the strength and fatigue resistivity of the pressure container.

Description

Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method

Technical field

The present invention relates to the design and implementation technology of the winding tension gradient of fiber in the fiber winding composite material pressure container.

Background technology

Fiber winding composite material pressure container is to be made by the continuous winding that the fiber behind the insulating varnish carries out on liner from level to level.At present,, normally adopt permanent tension force or the method for the tension force that simply successively decreases, indulge from inside to outside, hoop alternately twines both at home and abroad about the still comparatively imperfect applying method of pressure container fiber winding tension.In the composite material pressure container manufacturing process, under the winding tension effect, after the fibrage that is wrapped with all the fibrage that is wrapped with is earlier produced radial pressure, force radially to produce compressive deformation, thereby inner fiber fluffed.Adopt constant winding tension, make the goods fibrage produce the outer tight phenomenon of interior pine, thereby make ectonexine fiber initial stress produce very big difference; The method of tension force of simply successively decreasing considers just that also ferry stress changes in the winding process, can not realize accurately that the composite material ply stress along the requirement of wall thickness well-distributed, reduces the intensity and the fatigue property of container greatly.In winding process, winding tension is a key process parameter, and the performance of it and goods is closely related.Existing applying method is the whole mechanical property of difficulty performance winding layer, has influenced the performance of pressure container.

The innovation and creation content

The objective of the invention is to start with, a kind of Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method is provided, to improve the intensity and the anti-fatigue performance of pressure container from the fiber winding tension.

The invention provides a kind of Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method, mainly is that winding layer twines in the mode that the winding tension gradient is successively decreased from inside to outside.

In the above-mentioned Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method, the winding tension of each winding layer calculates with formula one:

$T\left(t_r\right)=K\frac{1}{t_r+t_{\mathrm{Mf}}}$ Formula one

In the formula: T _Tr---fiber tension;

t _r---fiber layer thickness (mm), $t_r=\underset{i=1}{\overset{r}{\mathrm{\Σ}}}\left(t_i\sin \mathrm{\α}\right),$ α represents the winding angle of i layer;

t _Mf---the conversion of metal inner lining thickness is the fiber equivalent thickness, that is: $t_{\mathrm{Mf}}=\frac{E_M}{E_f}{t}_M;$ E _MAnd E _fBe respectively metal and fiber isotropic modulus;

K---constant;

K＝T ₀·(t _Mf+t _f)

T ₀---outermost layer tension force (N/cm);

t _f---fiber layer thickness (cm), $t_f=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(t_i\sin \mathrm{\α}\right),$ α represents the winding angle of i layer.

Above-mentioned Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method concrete steps comprise:

1) determines thickness, the modulus of elasticity of pressure container metal inner lining, the modulus of elasticity of winding layer lamination coating, fiber initial stress, single layer fibre thickness and twine the number of plies;

2) calculate every layer of winding tension with formula one;

3) detecting and the controlling fiber winding process with the system controlled by computer tension system, wherein, with 2) winding tension of calculating is as the setting value of this system;

4) utilize this system controlled by computer tension system that the winding tension of winding process is detected in real time and adjust applying of winding tension, finish the winding overall process by the tension-applying mechanism in this system.

The present invention passes through accurate Calculation, take all factors into consideration the multiple factor in the pressure container forming process, design the gradient tension force that fiber twines, and control winding tension in the winding process by tension control system, thereby, make whole fibrages from inside to outside have identical initial stress, overcome the defective that the fibrage degree of tightness differs in the existing method, thereby improved the intensity and the fatigue resistance of container.

Description of drawings

Fig. 1 is the liner force diagram, show stress gradient by the controlling fiber layer after, the application stress level of metal inner lining significantly reduces.

Fig. 2 is embodiment one a design gradient tonogram, shows that the winding tension that applies changes in gradient.

Fig. 3 is a fiber Wound Pressure Vessels generalized section.

Fig. 4 is formula one change curve that tapers off.

The specific embodiment

By discovering, the winding tension applying method that generally uses at present makes the goods fibrage produce the degree of tightness state that differs, and its reason is that there is very big difference in ectonexine fiber initial stress.The technical matters that the present invention mainly solves is to eliminate the difference of initial stress between each fibrage, makes whole fibrages from inside to outside have identical initial stress, thereby container performance is improved.To this, the present invention proposes the gradient tension force design of fiber winding layer and applies scheme.

Discover that further the burst strength of fiber winding metal inner lining pressure container, cubic deformation rate, fatigue life, gum content etc. are all relevant with initial tension and the tension gradient selected.Subject matter of the present invention is the design of gradient tension force and applies.1, gradient tension force design calculation

The design of gradient tension force mainly comprises the design calculation of determining of fiber initial stress value and tension gradient value.(1) determines fiber initial stress value

Determine the fiber winding tension of composite material pressure container, need take all factors into consideration all multifactor influences.The present invention is from analyzing aspects such as liner rigidity, fibre strength and wearing and tearing, winding process, and provided computing formula.

Fiber winding composite material pressure container if the stress of metal inner lining is too high, the distortion is too big, causes early stage cracking easily under operation pressure, seepage takes place.Therefore, can be by the winding tension of controlling fiber, the stress of control liner makes container add repeatedly the process of unloading to inspection pressure from zero in interior pressure within a certain scope, and inner lining material can be in elastic stage work all the time.In order to realize this goal, when often requiring container to press in zero, liner is in compressive state.

In winding process, only strong mutual action between fiber and liner also is not a complex, obeys its Hooke's law separately.Liner produces compressive deformation under the winding tension effect, fiber produces tensile deformation.As shown in Figure 1, after C point and A point represent that respectively container has twined among Fig. 1, liner and the residing stress-strain state of fiber during interior pressure p=0.The work starting point of liner and fiber just.

In pressure process, liner becomes extended state from compressive state gradually.When interior pressure reached inspection pressure, the stress of inner lining material still was in below the elastic limit.Prestress in the fiber can improve the application stress of fiber, gives full play to the fiber high-strength characteristic, increase combined housing liner be in elastic stage bear in pressure energy power, the raising fatigue property.

Represented the drawing stress-strain of fiber and metallic material among Fig. 1.If fiber is not applied pretension stress, after then winding was finished, the state of stress in fiber and the metal inner lining all was in 0 point.By applying of gradient tension force, liner is in certain compressive state (the C point among the figure), and fiber is in extended state (the A point among the figure), and σ ₀t _f=σ _M0t _M0, i.e. σ ₀=σ _M0t _M0/ t _f

During the pressure container normal operation, the state of stress in interior pressure effect lower liner is from σ _M0(C point) changes to σ _M1(D point), the ferry stress state is from initial stress σ ₀(A point) changes to σ ₁(B point).

As seen by the prestressed degree of utilization that has improved fiber greatly that applies, reduced the liner stress level.

Certainly, winding tension should not make the liner unstability.Metal inner lining critical external pressure computing formula:

${\mathrm{\σ}}_{\mathrm{cr}}=\frac{E_M}{4(1-{\mathrm{\μ}}^2)}{\left(\frac{t_M}{R}\right)}^2$

In the formula, σ _Cr---liner unstability stress;

E _M---the modulus of elasticity of inner lining material;

The Poisson's ratio of μ---inner lining material;

t _M---thickness of inner lining;

R---liner radius;

(2) gradient tension force design

Gradient tension force design will make in the fiber Wound Pressure Vessels each layer fiber tension from inside to outside be certain graded exactly, and final purpose is to make each layer fiber that identical prestress be arranged, thus when the container normal operation whole structure of performance composite material.

Referring to Fig. 3, be fiber Wound Pressure Vessels generalized section, among Fig. 3, thickness is t _rThe fiber gradient tension force at place can calculate by formula one:

$T\left(t_r\right)=K\frac{1}{t_r+t_{\mathrm{Mf}}}$ Formula one

T in the formula _Tr---fiber tension;

t _r---fiber layer thickness (mm), $t_r=\underset{i=1}{\overset{r}{\mathrm{\Σ}}}\left(t_i\sin \mathrm{\α}\right),$ α represents the winding angle of each layer.

t _Mf---the conversion of metal inner lining thickness is the fiber equivalent thickness, that is: $t_{\mathrm{Mf}}=\frac{E_M}{E_f}{t}_M;$ (E _MAnd E _fBe respectively metal and fiber isotropic modulus)

K---constant;

K＝T ₀·(t _Mf+t _f)

T ₀---outermost layer tension force (N/mm), T ₀=σ ₀Δ t, Δ t are single layer fibre thickness;

t _f---fiber layer thickness (mm), $t_f=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(t_i\sin \mathrm{\α}\right),$ α represents the winding angle of i layer.

The function that formula one tapers off, as shown in Figure 4.

Formula one derivation:

Gradient tension force design will make in the fiber Wound Pressure Vessels each layer fiber tension from inside to outside be certain graded exactly, and final purpose is to make each layer fiber that identical prestress be arranged, thus when the container normal operation whole structure of performance composite material.

Composite layer is divided into the n layer, and each layer thickness is Δ t=t _f/ n, ground floor to each layer of outermost layer winding tension is followed successively by T ₁, T ₂... T _n, N/mm.All compressive deformation takes place with liner in fibrage, its hoop compressive force and this layer winding tension equal and opposite in direction, and direction is opposite.Winding tension as the second layer will force ground floor with liner compressive deformation to take place, and its compressive force equals second layer winding tension value.The winding tension of any i layer will force it to produce compressive deformation with whole winding layers of lining with liner, and its compressive force equals the winding tension value of i layer.

As seen, the actual stress of each layer fiber is each layer winding tension to the tensile stress that self produces and the whole outer winding tension compression effort sum to its generation, so:

${\mathrm{\σ}}_1=\frac{T_1}{\mathrm{\Δt}}-\frac{T_2}{\mathrm{\Δt}+t_{\mathrm{Mf}}}-\·\·\·\·\·\·-\frac{T_n}{(n-1)\mathrm{\Δt}+t_{\mathrm{mf}}}$

${\mathrm{\σ}}_2=\frac{T_2}{\mathrm{\Δt}}-\frac{T_3}{2\mathrm{\Δt}+t_{\mathrm{Mf}}}-\·\·\·\·\·\·-\frac{T_n}{(n-1)\mathrm{\Δt}+t_{\mathrm{Mf}}}$

Can get successively: ${\mathrm{\σ}}_n=\frac{T_n}{\mathrm{\Δt}}.$

The purpose of control winding tension is exactly that the initial stress of each layer fiber is equated, that is: σ ₁=σ ₂=...=σ _n=σ ₀By σ ₁=σ ₂, can get: $T_2=\frac{\mathrm{\Δt}+t_{\mathrm{Mf}}}{2\mathrm{\Δt}+t_{\mathrm{Mf}}}{T}_1$ By σ ₁=σ ₃, can get: $T_3=\frac{\mathrm{\Δt}+t_{\mathrm{Mf}}}{3\mathrm{\Δt}+t_{\mathrm{Mf}}}{T}_1$ Can get by that analogy: $T_j=\frac{\mathrm{\Δt}+t_{\mathrm{Mf}}}{\mathrm{i\Δt}+t_{\mathrm{Mf}}}{T}_1,$ $T_n=\frac{\mathrm{\Δt}+t_{\mathrm{Mf}}}{\mathrm{n\Δt}+t_{\mathrm{Mf}}}{T}_1$ Can get: $T_j=\frac{\mathrm{n\Δt}+t_{\mathrm{Mf}}}{\mathrm{i\Δt}+t_{\mathrm{Mf}}}{T}_n=\frac{t_f+t_{\mathrm{Mf}}}{t_r+t_{\mathrm{Mf}}}{T}_n$

If T _n=T ₀, because all each layer fiber initial stress all equate, so the outermost layer winding tension is: T ₀=σ ₀t _θOrder, K=T ₀(t _f+ t _Mf), then $T\left(t_r\right)=K\frac{1}{t_r+t_{\mathrm{Mf}}}$

2, tension force applies

The present invention is based on above-mentioned reasoning and method of calculating, in the specific implementation, need control applying of winding tension according to result of calculation.The control that applies of winding tension is that the tension control system by closed loop carries out.Tension control system is made up of computer center's control system, tension detection system and tension-applying mechanism three parts, walk around in the journey in biography, carry out tension force by central control system and set, and analyze, come the tensity of adjustment of tonicity applying mechanism by the feedback information of tension detection system.The MCTS-2000 type closed loop system controlled by computer tension system that can use Beijing glass-felt plastic research institute to develop among the present invention, tension force in the fiber winding process is detected in real time and controls, by the actual tension on the monitor monitoring yarn bundle, adjust winding tension in real time, it is kept in balance.Every layer of winding tension and actual set value error are no more than 2%.

Embodiment one: make 5 liters and 8 liters of composite material gas cylinders with aluminium alloy lining of winding method of the present invention.Integral structure is: aluminium alloy lining thickness is 2mm, and diameter is 100mm, totally 10 layers of composite material hoop winding layers, and vertical totally 8 layers of winding layers (4 circulations), winding angle is 20 °.Hoop and vertically every two-layer winding that replaces.Thickness in monolayer is 0.263mm.

Calculate with formula one,

Design liner stress ${\mathrm{\σ}}_{\mathrm{cr}}=\frac{E}{4(1-{\mathrm{\μ}}^2)}{\left(\frac{t_M}{R}\right)}^2=\frac{72000}{4\×(1-{0.3}^2)}\×{\left(\frac{2}{50}\right)}^2=31.6\mathrm{MPa},$ Get 31MPa.

Design fiber initial stress σ ₀=σ _Mt _M/ t _f=31 * 2 ÷ 3.35=18.5MPa.Therefore, the fiber initial tension is T ₀=18.5 * 0.263=4.97 (N/mm)

t _Mf＝70/200×2＝0.7mm，t _f＝0.263×10+0.263×8×sin20°＝3.35mm。

K＝T ₀·(t _Mf+t _f)＝4.97×(0.7+3.35)＝20.1

$T\left(t_r\right)=K\frac{1}{t_r+t_{\mathrm{Mf}}}=20.1\×\frac{1}{t_r+0.7}(N/\mathrm{mm})$

Tension force is got every two-layer as the unit that successively decreases when implementing, then hoop tension force computing value is:

The winding layer sequence number	????t r(mm)	Tension force (N/mm)
			????1	????0.26	????20.9
????2	????0.53	????16.3
			????3	????0.97	????12.0
????4	????1.24	????10.4
			????5	????1.68	????8.4
????6	????1.95	????7.6
			????7	????2.39	????6.5
????8	????2.65	????6.0
			????9	????3.10	????5.3
????10	????3.35	????4.9

This hoop winding tension gradient as shown in Figure 2.Use MCTS-2000 type closed loop system controlled by computer tension system that winding tension is monitored in real time and adjusted, with computing value as micro-processor controlled setting value, actual value of applying of every layer of winding tension is no more than 1% with the setting value error, finishes gradient Tonofibrils winding process according to this.

Embodiment two: make 2 liters and 4 liters of composite material gas cylinders with steel alloy liner of winding method of the present invention.Integral structure is: steel alloy liner 2mm, diameter are 100mm, totally 6 layers of composite material hoop winding layers, and vertical totally 4 layers of winding layers (2 circulations), winding angle is 20 °.Hoop and vertically every two-layer winding that replaces.Thickness in monolayer is 0.263mm.

Calculate with above-mentioned formula

Design liner stress ${\mathrm{\σ}}_{\mathrm{cr}}=\frac{E}{4(1-{\mathrm{\μ}}^2)}{\left(\frac{t_M}{R}\right)}^2=\frac{210000}{4\×(1-0.3^2)}\×{\left(\frac{2}{50}\right)}^2=92.2\mathrm{MPa},$ Get 92Mpa.

Design fiber initial stress σ ₀=σ _Mt _M/ t _f=92 * 2 ÷ 1.94=95MPa.Therefore, the fiber initial tension is T ₀=95 * 0.263=25 (N/mm) t _Mf=210/200 * 2=2.1mm, t _f=0.263 * 6+0.263 * 4 * sin20=1.94mm.K＝T ₀·(t _Mf+t _f)＝25×(2.1+1.94)＝101MPa

$T\left(t_r\right)=K\frac{1}{t_r+t_{\mathrm{Mf}}}=101\×\frac{1}{t_r+2.1}$

Tension force is got every two-layer as the unit that successively decreases when implementing, then computing value is:

Sequence number	????t r(mm)	Tension force (N/mm)
			????1	????0.53	????38.4
????2	????1.23	????30.3
			????3	????1.93	????25.0

Use MCTS-2000 closed loop system controlled by computer tension system that winding tension is monitored in real time and adjusted, with computing value as micro-processor controlled setting value, the value of applying of every layer of winding tension is no more than 1% with the setting value error, finishes the gradient Tonofibrils winding process of setting.

The foregoing description composite material gas cylinder is tested,

1, bursting pressure test: (GJB392-87) carry out hydraulic bursting test according to " aviation glass fiber reinforced plastic pressure container ".

The container model	2 liters	4 liters	5 liters	8 liters
					Adopt constant-tension	????70MPa	????75MPa	????80MPa	????78MPa
Adopt the tension force that simply successively decreases	????76MPa	????81MPa	????84MPa	????83MPa
					Adopt gradient tension force of the present invention	????92MPa	????96MPa	????103MPa	????92MPa

Test result: with the container that traditional winding method is made, the bursting pressure value has improved 10～20%;

2, fatigue life test: (GJB392-87) carry out hydraulic bursting test according to " aviation glass fiber reinforced plastic pressure container ".

The container model	2 liters	4 liters	5 liters	8 liters
					Adopt constant-tension	6800 times	8000 times	7600 times	7800 times
Adopt the tension force that simply successively decreases	7000 times	8500 times	7500 times	8000 times
					Adopt gradient tension force of the present invention	10000 times	16000 times	11000 times	12000 times

Fatigue life, test result was also brought up to more than 10000 times by original 7000～8000 times.

Above-mentioned experiment shows, by fiber gradient tension force design and implementation technology in the composite material pressure container Applications in Fabrication, not only improved the work strained condition of metal inner lining but also improved the overall performance of composite material, the burst strength of container, fatigue life are all improved greatly.

Claims (3)

1, a kind of Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method is characterized in that, winding layer twines in the mode that the winding tension gradient is successively decreased from inside to outside.

2, Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method according to claim 1 is characterized in that, the winding tension of described each winding layer calculates with formula one:

$T\left(t_r\right)=K\frac{1}{t_r+t_{\mathrm{Mf}}}$

Formula one

In the formula: T _Tr---fiber tension;

t _r---fiber layer thickness (mm), $t_r=\underset{i=1}{\overset{r}{\mathrm{\Σ}}}\left(t_r\sin \mathrm{\α}\right),$ α represents the winding angle of each layer;

t _Mf---the conversion of metal inner lining thickness is the fiber equivalent thickness, that is: $t_{\mathrm{Mf}}=\frac{E_M}{E_f}{t}_M;$ E _MAnd E _fBe respectively

Metal and fiber isotropic modulus;

K---constant;

K＝T ₀·(t _Mf+t _f)

T ₀---outermost layer tension force (N/cm);

t _f---fiber layer thickness (cm), $t_f=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left(t_i\sin \mathrm{\α}\right),$ α is an i layer winding angle.

3, Filament-wound Composite Pressure Vessels Imposed Tension Gradient Method according to claim 1 and 2 is characterized in that, concrete steps comprise:

1) determines thickness, the modulus of elasticity of pressure container metal inner lining, the modulus of elasticity of winding layer lamination coating, fiber initial stress, single layer fibre thickness and twine the number of plies;

2) calculate every layer of winding tension with formula one;

3) detecting and the controlling fiber winding process with the system controlled by computer tension system, wherein, with 2) winding tension of calculating is as the setting value of this system;

4) utilize this system controlled by computer tension system that the winding tension of winding process is detected in real time and adjust applying of winding tension, finish the winding overall process by the tension-applying mechanism in this system.

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