CN108416175A - Long fiber composites rear seat of passenger car skeleton original material design method - Google Patents
Long fiber composites rear seat of passenger car skeleton original material design method Download PDFInfo
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Abstract
The invention belongs to composite material for cars research fields, are related to a kind of long fiber composites rear seat of passenger car skeleton original material design method.Include the following steps：1, rear seat of passenger car minibus requirement is determined；2, LFT tablet critical impact energy expression formulas are derived；3, research requires lower LFT plate material design methods based on impact energy；4, seat back skeleton original material is designed；5, initial designs result finite element and experiment are verified；The present invention sets up energy absorption capability and material parameter and the bridge of experiment constraints parameter association with LFT tablet critical impact energies, on the one hand estimates LFT tablet limit impact energys, on the other hand instructs LFT materials initial designs and selection；The application of practical meaning in engineering of the present invention is assumed that in the case where determining impact operating mode, the approximate range of absorption impact energy is needed from the angle initialization LFT tablets of safety coefficient, LFT material fibers volume fraction and corresponding slab-thickness is calculated, realizes material initial designs.
Description
Technical field
The present invention relates to a kind of rear seat of passenger car skeleton original materials for belonging to composite material for cars research field
Design method, it more particularly relates to which a kind of long fiber composites rear seat of passenger car skeleton original material is set
Meter method.
Background technology
Seat is relatively independent car body component in automotive body structure, has corresponding regulation to its rigidity and intensity etc.
Performance claims.Wherein, it for rear seat of passenger car, needs to carry out luggage case block impact test to investigate its anti-impact
Performance is hit, to ensure that seat will not damage heel row occupant during head-on crash.
Traditional metal armchair structure in order to meet the requirement of performance, most common measure be exactly increase structural thickness, though
So it ensure that performance but the thing followed are the increases of seat quality.Currently, using fibre reinforced composites as the light weight of representative
Change material gradually attempting to replace metal material, and has certain light weight effect.However, due to analogue technique and design side
The deficiency of method often needs blindly largely to be manufactured experimently and experimental test at seat design initial stage, increase exploitation at
This.Using long fiber reinforced thermoplastic composites (Long Fiber reinforced Thermoplastics, abbreviation LFT)
Energy absorption analysis model and LFT material initial designs methods, can be rapidly completed and be wanted for luggage case block impact test properties
The design of LFT the seat back skeleton initial configuration and material asked.
Invention content
The present invention in order to complete to design rear seat of passenger car skeleton original material, using LFT energy absorptions model and
LFT material initial designs methods are main means, and propose a kind of long fiber composites rear seat of passenger car bone with this
Frame original material design method.
In order to solve the above technical problems, the present invention adopts the following technical scheme that realization：
A kind of long fiber composites rear seat of passenger car skeleton original material design method, includes the following steps：
Step 1：Determine rear seat of passenger car minibus requirement；
Step 2：Derive LFT tablet critical impact energy expression formulas；
Step 3：Research requires lower LFT plate material design methods based on impact energy；
Step 4：Design seat back skeleton original material；
Step 5：Verify initial designs result finite element and experiment.
Determination rear seat of passenger car minibus described in step 1 require, in particular to：
(1) according in GB15083-2006《The test method of luggage displacement occupant restraint device》, for back row seat of automobile
The certification of chair impact strength provides, the impact test of seat is carried out using sled test platform；
(2) test sample block size is 300mm × 300mm × 300mm, edge chamfering 20mm, quality 18kg, test sample
Block installation is placed on the floor of luggage compartment, longitudinal horizontal distance for having 200mm with skeleton；
(3) test sample block is two pieces, has the lateral distance of 50mm between two test sample blocks, what trolley was applied in experiment subtracts
Rate curve meets《The test method of luggage displacement occupant restraint device》It is required that；
(4) during testing and after experiment, if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements；
During experiment, chair framework and its fastener is allowed to deform, condition be test the front profile of skeleton and head rest cannot be to
Front is beyond a lateral vertical plane, and to head rest, this plane passes through seat R-point, i.e. point at R points front 150mm；To seat
Chair skeleton part, this plane is by the point at 100mm in front of seat R points.
Derivation LFT tablet critical impact energy expression formulas described in step 2, include the following steps：
First, determining LFT tablets critical impact energy, there is power function relationships with LFT tablet fibers overall thickness：
Using the density value of glass fibre and PP matrixes, fiber quality score is scaled fiber volume fraction Vf, then count
Calculation obtains fiber total thickness t × V of form of ownership LFT tabletsf, by critical impact energy Umin pFormula (1) is pressed with fiber overall thickness
Nonlinear fitting is carried out, is as a result shown in logarithmic coordinates system；
Umin p=K × (t × Vf)β (1)
K and β is by the determining material parameter of experiment in formula；
Second, the residual speed after the drop impact difference fiber quality score tablet of different-diameter is rushed with initial respectively
Speed is hit, and nonlinear fitting is carried out using formula (2), obtains critical speed of dropping hammer；
Wherein：vrFor the rebound velocity that drops hammer, vlFor critical speed of dropping hammer, v0For initial impact speed of dropping hammer, k is that fitting is joined
Number；
Third calculates the critical speed of all tablets that fitting obtains according to formula (3), obtains difference and drops hammer diameter
When LFT tablets critical impact energy Umin p；
mpExpression is dropped hammer quality；
4th, the critical impact energy of the different diameters that drop hammer is subjected to nonlinear fitting using formula (4), fitting result is drawn
In figure, obtain difference drop hammer diameter impact when, critical impact energy and fiber overall thickness logarithmic plot；
Umin p=K × (t × Vf)β (4)
In formula：K and β is by the determining material parameter of experiment, and t is slab-thickness, VfFor fiber volume fraction；
5th, formula (4) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as certainly
Variable, shown in formula (5)：
Umin p=K (tVf·Dt)β (5)
DtExpression is dropped hammer diameter；
6th：By comparing the theoretical calculation and simulation result of LFT tablet critical impact energies, minimal penetration is verified
The accuracy of energy theory expression formula.
Research described in step 3 is based on impact energy and requires lower LFT plate material design methods, includes the following steps：
First：Using critical impact energy as bridge, it is established that tablet energy-absorbing requires the relationship between material parameter
Formula (8)；
Known LFT energy absorptions analysis model is：
Acquire Umin pFor：
Wherein UimpFor drop impact energy, UabsEnergy, U are absorbed for tabletimpAnd UabsValue range be [0,
Umin p]；
Formula (5) and (7), which are combined, must contact：
Then：On the one hand estimate LFT tablet limit impact energys using formula (8), LFT materials is on the other hand instructed initially to set
Meter and selection：
Assuming that thickness, the fiber volume fraction of the known LFT tablets, and assume impact body diameter, while understanding impact body
The energy-absorbing requirement of tablet, i.e. U when reboundabsIt has been determined that from right to left according to formula (8), impact body limit impact energy is calculated
Amount, and then acquire the limit impact initial velocity of impact body；
Assuming that in the case where determining the two impact working conditions of impact energy and impact body diameter, from the angle of safety coefficient,
Setting LFT tablets need the approximate range for absorbing impact energy to be calculated from left to right according to (8), obtain LFT material fiber bodies
Fraction and corresponding slab-thickness, realize the initial designs of material.
Seat back skeleton original material, including content in detail below are designed described in step 4：
Luggage case block Shock Environmental Condition is simplified, the first of material is carried out to LFT seat back plate structures using formula (8)
The design that begins and selection；
Backboard is impacted as research object using single luggage block, is reduced to drop impact LFT slab constructions, definition is dropped hammer
Diameter, quality and initial impact speed, wherein the length of side of luggage block to be considered as to the diameter to drop hammer；
Be not pierced from tablet and safety coefficient from the point of view of, calculate separately, when tablet absorbs energy Uabs, account for and drop hammer
LFT fiber qualities score when the ratio of impact energy is 100%, 90%, 80% and 70% and corresponding slab-thickness, after the completion
Arrange the initial designs of seat back skeleton.
Initial designs result finite element and experiment are verified described in step 5, are included the following steps：
(1) a kind of LFT materials of mass fraction are selected, the metal material of back seat backboard skeleton is replaced, utilization is limited
Meta analysis software establishes the simulation model of luggage case block impact test, by the finite element model of foundation and sled test result pair
Than verifying the validity of LFT material models；
(2) backboard skeleton thickness is adjusted, carries out calculating the satisfactory seat back thickness value of acquisition, be inhaled with based on energy
It is close to receive the seat back plate structure initial designs method thickness value that analysis model carries out；It is proved with this, is analyzed using energy absorption
Model carries out LFT seat back plate structures the feasibility and validity of original material design.
Compared with prior art the beneficial effects of the invention are as follows：
1. long fiber composites rear seat of passenger car skeleton original material design method of the present invention considers multiple
The strain rate effect that condensation material mechanical characteristic is shown, by nonlinear fitting set up critical impact energy and material parameter and
Relationship between parameter of dropping hammer.
2. long fiber composites rear seat of passenger car skeleton original material design method of the present invention is flat with LFT
Plate critical impact energy sets up energy absorption capability and material parameter and the bridge of experiment constraints parameter association.On the one hand
It can estimate LFT tablet limit impact energys, on the other hand can instruct LFT materials initial designs and selection.Assuming that known should
The thickness of LFT tablets, fiber volume fraction and impact condition, at the same when understanding impact rebound tablet energy-absorbing requirement, then can be with
Impact body limit impact energy is calculated, and then acquires the limit initial velocity of impact body.In addition, having more the practical meaning of engineering
The application of justice is assumed that in the case where determining impact operating mode, needs to absorb impact energy from the angle initialization LFT tablets of safety coefficient
LFT material fibers volume fraction and corresponding slab-thickness can be calculated in approximate range, realize material initial designs.
Description of the drawings
The present invention will be further described below with reference to the drawings：
Fig. 1 is the flow of long fiber composites rear seat of passenger car skeleton original material of the present invention design
Figure；
Fig. 2 is the test sample of long fiber composites rear seat of passenger car skeleton original material of the present invention design
Block quality and its layout drawing；
Fig. 3 is that the trolley of long fiber composites rear seat of passenger car skeleton original material of the present invention design subtracts
Speed curve diagram；
Fig. 4 is that the LFT of long fiber composites rear seat of passenger car skeleton original material of the present invention design is flat
Plate critical impact energy and fiber overall thickness logarithmic plot；
Fig. 5-1 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 20%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 24mm；
Fig. 5-2 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 30%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 24mm；
Fig. 5-3 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 40%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 24mm；
Fig. 6-1 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 20%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 16mm；
Fig. 6-2 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 30%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 16mm；
Fig. 6-3 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 40%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 16mm；
Fig. 7-1 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 20%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 8mm；
Fig. 7-2 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 30%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 8mm；
Fig. 7-3 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 40%LFT tablets drop hammer residual speed and initial impact speed curve diagram when diameter 8mm；
Fig. 8 is that the difference of long fiber composites rear seat of passenger car skeleton original material of the present invention design is fallen
Critical impact energy and fiber overall thickness logarithmic plot when hammering diameter impact into shape；
Fig. 9 is that the minimum of long fiber composites rear seat of passenger car skeleton original material of the present invention design is worn
The logarithmic plot of saturating energy and fiber overall thickness and diameter product of dropping hammer；
Figure 10 is the minimum of long fiber composites rear seat of passenger car skeleton original material of the present invention design
Penetrating capacity theoretical calculation is to simulation result comparison diagram；
Specific implementation mode
The present invention is explained in detail below in conjunction with the accompanying drawings：
Long fiber composites rear seat of passenger car skeleton initial designs method flow diagram such as Fig. 1 institutes of the present invention
Show, first, in accordance with relevant laws and regulations, the clear minibus requirement for rear seat of passenger car erects limit element artificial module；
Secondly, it is established that the relationship between LFT tablets critical impact energy and slab-thickness, fiber volume fraction and drop impact, it is complete
It is derived at critical impact energy expression formula；Then, according to the critical impact energy of LFT tablets both with drop impact energy and tablet
It is related and related to material fiber overall thickness and the diameter that drops hammer to absorb energy, therefore is built using critical impact energy as bridge
It erects tablet energy-absorbing and requires contacting between Material Design；Then, luggage case block Shock Environmental Condition is simplified,
Initial designs and the selection of material are carried out to LFT seat back plate structures using LFT plate materials design method；Finally, by having
The fiber quality score of selection and the seat back skeleton of thickness are verified in the first emulation mode of limit or experiment trial-production, it was demonstrated that material
Expect the validity of design method.
The long fiber composites rear seat of passenger car skeleton original material design method is as follows：
1. determining the requirement of rear seat of passenger car minibus
In GB15083-2006《The test method of luggage displacement occupant restraint device》It is strong for automobile rear seat impact
The certification of degree provides to carry out the impact test of seat using sled test platform.Test sample block size be 300mm × 300mm ×
300mm, edge chamfering 20mm, quality 18kg.The position of test sample block installation is as shown in Fig. 2, place the ground with luggage compartment
On plate, longitudinal horizontal distance for having 200mm with skeleton；The lateral distance for having 50mm between two test sample blocks, trolley institute in experiment
The projectile deceleration history of application is as shown in Figure 3.
During experiment and experiment after if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements.It is trying
During testing, chair framework and its fastener is allowed to deform, condition is to test skeleton and the front profile of head rest cannot be forwards
Beyond a lateral vertical plane, to head rest, this plane passes through seat R-point, i.e. point at R points front 150mm；To seat bone
Frame part, this plane is by the point at 100mm in front of seat R points.
2.LFT tablet critical impact energy expression formulas derive
G.Caprino has found that penetrating capacity not only has phase with material parameter when studying composite laminated plate impact characteristics
Closing property and with diameter this loading environment existence function relationship of dropping hammer.It is not difficult to find out that LFT tablet critical impact energies are contacts
Energy absorption capability and material parameter and the important bridge of experiment constraints parameter.
The product of composite material laminated board middle plateform thickness and fiber volume fraction is defined as fiber overall thickness, is to influence
The major parameter of penetrating capacity, and there are power function relationships with it.Using the density value of glass fibre and PP matrixes by cellulosic
Amount score is scaled fiber volume fraction Vf, then fiber overall thickness (t × V of form of ownership LFT tablets has been calculatedf), it will most
Small penetrating capacity Umin pNonlinear fitting is carried out by formula (1) with fiber overall thickness, is as a result shown in logarithmic coordinates system.
Umin p=K × (t × Vf)β (1)
K and β is by the determining material parameter of experiment in formula.
Determining LFT tablets critical impact energy, there is power function relationships with its fiber overall thickness.
Unquestionably, it is flat that the variation for shape of dropping hammer under the premise of drop impact energy is constant can seriously affect composite material
The penetrating capacity of plate, wherein the diameter that drops hammer is typical geometric parameter.Therefore, that tup quality in drop impact model is certain
Under the premise of, carry out a variety of tup diameter calculations.
Respectively to the residual speed and initial impact speed after the drop impact difference fiber quality score tablet of different-diameter
Degree, and nonlinear fitting is carried out using formula (2), obtain critical speed of dropping hammer.
Wherein vrFor the rebound velocity that drops hammer, vlFor critical speed of dropping hammer, v0For initial impact speed of dropping hammer, k is that fitting is joined
Number.
The critical speed of all tablets that fitting obtains is calculated according to formula (3), obtain difference drop hammer diameter when LFT
The critical impact energy U of tabletmin p。
The critical impact energy of the different diameters that drop hammer is subjected to nonlinear fitting using formula (4), fitting result is drawn on figure
In, obtain difference drop hammer diameter impact when critical impact energy and fiber overall thickness logarithmic plot.
Umin p=K (tVf)β (4)
It can be seen that the curve being fitted under the different diameters that drop hammer will not intersect in research range, in addition it is approximate mutually equal
Row.Therefore, formula (4) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as independent variable,
As shown in formula (5).
Umin p=K (tVf·Dt)β (5)
The LFT tablets critical impact energy obtained under the conditions of different-diameter drop impact is subjected to Nonlinear Quasi with formula (5)
It closes, obtains the expression formula of critical impact energy.
By comparing the theoretical calculation and simulation result of LFT tablet critical impact energies, critical impact energy is verified
The accuracy of theoretical expression.
3. requiring lower LFT plate material design method researchs based on impact energy
The critical impact energy of LFT tablets was not only related to drop impact energy and tablet absorption energy, but also and material fiber
Overall thickness and diameter correlation of dropping hammer, therefore can set up the requirement of tablet energy-absorbing and material using critical impact energy as bridge
Relationship between parameter.
Known LFT energy absorptions analysis model is：
It can be in the hope of Umin pFor：
Wherein UimpFor drop impact energy, UabsEnergy, U are absorbed for tabletimpAnd UabsValue range be [0,
Umin p]。
Formula (5) and (7), which are combined, must contact：
In the case where energy absorption analysis model determines, it on the one hand can estimate that the LFT tablet limit are impacted using formula (8)
On the other hand energy can instruct LFT materials initial designs and selection.Assuming that the thickness of the known LFT tablets, fiber volume fraction
The diameter of number and impact body, while understanding the energy-absorbing requirement of tablet when impact body is sprung back, i.e. UabsIt has been determined that then according to formula (8) from
Impact body limit impact energy is calculated in right-to-left, and then acquires the limit impact initial velocity of impact body.In addition it has more
The application of practical meaning in engineering assumes that under the conditions of determining impact energy and impact body diameter, from the angle initialization of safety coefficient
LFT tablets need to absorb the approximate range of impact energy, then LFT material fiber bodies can be calculated from left to right according to (8)
Fraction and corresponding slab-thickness, realize the initial designs of material.
4. seat back skeleton original material designs
First luggage case block Shock Environmental Condition is simplified, to carry out material to LFT seat back plate structures using formula (8)
The initial designs of material and selection.The structure type of rear seat of passenger car generally use " four or six points " and " five or five points ", in luggage
Block can be approximately considered the seat back plate structure that each luggage block only hits the front when impacting, between there is no reciprocal effect.Cause
This, using single luggage block impact backboard as research object, be reduced to drop impact LFT slab constructions, define drop hammer it is straight
Diameter, quality and initial impact speed, wherein the length of side of luggage block to be considered as to the diameter to drop hammer.It is not pierced from tablet and safety is
From the point of view of number, calculate separately when tablet absorbs energy UabsThe ratio for accounting for drop impact energy is 100%, 90%, 80% He
LFT fiber qualities score when 70% and corresponding slab-thickness complete the initial designs of heel row seat back skeleton.
5. initial designs result finite element and verification experimental verification
It selects a kind of LFT materials of mass fraction to replace the metal material of back seat backboard skeleton, utilizes finite element fraction
Analysis software establishes the simulation model of luggage case block impact test to simulate, by the finite element model of foundation and sled test result pair
Than verifying the validity of LFT material models.
On this basis, the thickness value and be based on energy absorption analysis model that adjustment backboard skeleton thickness is calculated
It is close that original material design thickness is carried out to LFT seat back plate structures, it was demonstrated that using energy absorption analysis model to LFT seat backs
Harden structure carries out the feasibility and validity of original material design.
Embodiment：
Next the present invention combines example introduction to utilize long fiber composites rear seat of passenger car proposed by the present invention
The process of skeleton original material design method.
1. determining the requirement of rear seat of passenger car minibus
In GB15083-2006《The test method of luggage displacement occupant restraint device》It is strong for automobile rear seat impact
The certification of degree provides to carry out the impact test of seat using sled test platform.Test sample block size be 300mm × 300mm ×
300mm, edge chamfering 20mm, quality 18kg.The position of test sample block installation is as shown in Fig. 2, place the ground with luggage compartment
On plate, longitudinal horizontal distance for having 200mm with skeleton；The lateral distance for having 50mm between two test sample blocks, trolley institute in experiment
The projectile deceleration history of application is as shown in Figure 3.
During experiment and experiment after if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements.It is trying
During testing, chair framework and its fastener is allowed to deform, condition is to test skeleton and the front profile of head rest cannot be forwards
Beyond a lateral vertical plane, to head rest, this plane passes through seat R-point, i.e. point at R points front 150mm；To seat bone
Frame part, this plane is by the point at 100mm in front of seat R points.
2.LFT tablet critical impact energy expression formulas derive
Calculated diameter is the drop impact model of 24mm, and LFT tablet critical impact energies are as shown in table 1, utilize glass fibers
Fiber quality score is scaled fiber volume fraction V by the density value of peacekeeping PP matrixesf, then form of ownership LFT is calculated and puts down
Fiber overall thickness (t × V of platef), by critical impact energy Umin pWith fiber overall thickness nonlinear fitting, knot are carried out by formula (1)
Fruit shows in logarithmic coordinates system sees Fig. 4.
Table 1LFT tablet critical impact energies
| ω=20% | ω=30% | ω=40% | |
| T=2mm | 8.58 | 11.16 | 15.02 |
| T=3mm | 14.02 | 17.82 | 21.33 |
| T=4mm | 20.43 | 24.93 | 27.98 |
K=30.69 in fitting result, β=0.702, R2=0.914, show that calculate data has with fit correlation curve
Good consistency.LFT tablets critical impact energy is determined, and there is power function relationships with its fiber overall thickness.
Shape of dropping hammer under the premise of drop impact energy is constant can seriously affect the penetrating capacity of composite material flat plate,
In the diameter that drops hammer be typical geometric parameter, ensure that the quality of tup is 1kg, a diameter of 24mm be set, and 16mm and 8mm are counted
It calculates.
The drop impact difference fiber quality score that Fig. 5, Fig. 6 and Fig. 7 list a diameter of 24mm, 16mm and 8mm respectively is flat
Residual speed after plate and initial impact speed, and nonlinear fitting is carried out to data using formula (2).Parameter is shown in fitting result
Table 2, table 3 and table 4.It can clearly be seen that each matched curve and data all have extraordinary consistency.
Table 2 drops hammer the LFT tablet critical speed fitting parameters of a diameter of 24mm
| LFT flat types | vl | k | R2 |
| T=2mm, ω=20% | 4.14 | 1.80 | 0.999 |
| T=3mm, ω=20% | 5.30 | 1.81 | 0.999 |
| T=4mm, ω=20% | 6.40 | 1.84 | 0.999 |
| T=2mm, ω=30% | 4.72 | 1.84 | 0.999 |
| T=3mm, ω=30% | 5.97 | 1.90 | 0.999 |
| T=4mm, ω=30% | 7.06 | 1.83 | 0.999 |
| T=2mm, ω=40% | 5.48 | 1.88 | 0.999 |
| T=3mm, ω=40% | 6.53 | 1.87 | 0.999 |
| T=4mm, ω=40% | 7.84 | 1.79 | 0.999 |
Table 3 drops hammer the LFT tablet critical speed fitting parameters of a diameter of 16mm
Table 4 drops hammer the LFT tablet critical speed fitting parameters of a diameter of 8mm
By the critical speed of all tablets that fitting obtains according to formula (3) be calculated difference drop hammer diameter when LFT
Critical impact energy Umin p, result of calculation is as shown in table 5.
Table 5 drop hammer diameter 24mm, 16mm and 8mmm when LFT tablet critical impact energies
The critical impact energy of drop hammer a diameter of 24mm, 16mm and 8mm are subjected to nonlinear fitting, fitting using formula (4)
As a result be drawn in figure, obtain difference drop hammer diameter impact when critical impact energy and fiber overall thickness logarithmic plot, such as Fig. 8
It is shown.As can be seen from the figure the curve being fitted under three diameters that drop hammer will not intersect in research range, or even approximate mutual
It is parallel.Therefore formula (4) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as change certainly
Amount, nonlinear fitting is carried out by the LFT tablets critical impact energy obtained under the conditions of three kinds of diameter drop impacts with formula (5), is intended
Comparing result such as Fig. 9 of curve and data after conjunction, it can be seen that the two has good consistency.Critical impact energy at this time
Expression formula be：
Umin p=1.72 (tVf·Dt)0.928 (9)
Wherein, fitting variance R2=0.901.Figure 10 compares the calculated results of LFT tablet critical impact energies, can be with
Find out that most data point is distributed in ± 10% error range, demonstrates the accurate of critical impact energy theoretical expression
Property.
3. requiring lower LFT plate material design method researchs based on impact energy
The critical impact energy of LFT tablets was not only related to drop impact energy and tablet absorption energy, but also and material fiber
Overall thickness and diameter correlation of dropping hammer, therefore can set up the requirement of tablet energy-absorbing and material using critical impact energy as bridge
Relationship between parameter.
Known LFT energy absorptions analysis model is formula (7), can be in the hope of Umin pFor formula (8), formula (7) and (9) are combined
It can must contact：
In the case where energy absorption analysis model determines, it on the one hand can estimate that the LFT tablet limit are rushed using formula (10)
Energy is hit, LFT materials initial designs and selection on the other hand can be instructed.Assuming that the thickness of the known LFT tablets, fiber volume
Score and impact body diameter this impact condition, at the same when understanding impact body rebound tablet energy-absorbing requirement, i.e. UabsIt has been determined that
Impact body limit impact energy is then calculated according to formula (10) from right to left, and then acquires the initial speed of limit impact of impact body
Degree.In addition it is assumed that with more the application of practical meaning in engineering in the case where determining impact working condition, i.e. UimpWith impact body diameter
It determines, the approximate range for absorbing impact energy is needed from the angle initialization LFT tablets of safety coefficient, then it can be according to (10) from a left side
LFT material fibers volume fraction and corresponding slab-thickness is calculated to the right side, realizes the initial designs of material.
4. seat back skeleton original material designs
Luggage case block Shock Environmental Condition is simplified, to carry out material to LFT seat back plate structures using formula (10)
The initial designs of material and selection.The rear seat of passenger car structure type for choosing " four or six points ", can be close when luggage block impacts
Seemingly think that each luggage block only hits the seat back plate structure of the front, between do not influence.Therefore, it is impacted with single luggage block
Backboard is research object, is reduced to drop impact LFT slab constructions, and it is 300mm, i.e. luggage block to define the diameter Dt to drop hammer
The length of side, quality 18kg, initial impact speed be 8.57m/s, so the initial impact energy U to drop hammermin pFor 660J.From flat
Plate is not hungry penetrate and safety coefficient from the point of view of, calculate separately when tablet absorbs energy UabsAccount for the ratio of drop impact energy
LFT fiber qualities score and corresponding slab-thickness when being 100%, 90%, 80% and 70%.
The fiber quality fraction range of usually used LFT is 20% to 50% in automotive body structure.Therefore, formula is utilized
(10) the LFT slab-thickness t for being 20%, 30%, 40% and 50% to mass fraction is calculated, corresponding fiber volume fraction
For：9.77%, 15.7%, 22.4% and 30.2%, the results are shown in Table 6.
Material thickness calculates under 6 different quality containing LFT material difference safety coefficients of table
As can be seen from the table with the increase of fiber quality score, each thickness for absorbing LFT tablets under energy condition
Also reduce therewith, maximum value is about times of minimum value.When the ratio for absorbing energy and impact energy is gradually reduced, i.e., safety coefficient increases
When big, slab-thickness also obviously increases, and maximum value is about 8 times of minimum value.
Initial designs can be carried out to back seat backboard skeleton, according to data in table when the best fibre of selection mechanical property
When tieing up the LFT of mass fraction 50%, the minimum thickness of seat back is 12.33mm；As the LFT of selection fiber quality score 40%
When, the minimum thickness of backboard is 16.62mm, and so on.
5. initial designs result finite element and verification experimental verification
Fiber quality score is selected to replace the metal material of back seat backboard skeleton for 50% LFT, armchair structure adopts
With the form of " four or six points ".The top of two parts backboard skeleton is connected by center latch with body construction, during bottom then utilizes
Between and two side stands connect with body construction.
Luggage case block impact test simulation model is established using finite element software Ls-Dyna, wherein LFT is used 24 in software
On the one hand the simulation of number elastic-plastic material model considers that the distribution randomness bigger of the fiber when fiber quality score is 50% can
Isotropic material is regarded as with approximation, is on the other hand to improve computational efficiency.Pass through setting failure plasticity in material model
Strain comes whether judgement material is destroyed.
By the finite element model of foundation and sled test Comparative result, the validity of LFT isotropic material models is verified,
The grid of finite element model is exactly to be established according to the geometrical model of preproduction workpiece.
On this basis, adjustment backboard skeleton thickness is calculated, it is found that chair framework can expire when thickness is 15mm
Sufficient laws and regulations requirement, this result, which can prove amply, carries out initially LFT seat back plate structures using energy absorption analysis model
The feasibility and validity of design of material.
Claims (6)
1. a kind of long fiber composites rear seat of passenger car skeleton original material design method, which is characterized in that including with
Lower step：
Step 1：Determine rear seat of passenger car minibus requirement；
Step 2：Derive LFT tablet critical impact energy expression formulas；
Step 3：Research requires lower LFT plate material design methods based on impact energy；
Step 4：Design seat back skeleton original material；
Step 5：Verify initial designs result finite element and experiment.
2. a kind of long fiber composites rear seat of passenger car skeleton original material design side according to claim 1
Method, it is characterised in that：
Determination rear seat of passenger car minibus described in step 1 require, in particular to：
(1) according in GB15083-2006《The test method of luggage displacement occupant restraint device》, automobile rear seat is rushed
The certification of hit intensity provides, the impact test of seat is carried out using sled test platform；
(2) test sample block size is 300mm × 300mm × 300mm, edge chamfering 20mm, quality 18kg, test sample block peace
It puts and sets on the floor of luggage compartment, longitudinal horizontal distance for having 200mm with skeleton；
(3) test sample block is two pieces, there is the lateral distance of 50mm, the deceleration that trolley is applied in experiment between two test sample blocks
Curve meets《The test method of luggage displacement occupant restraint device》It is required that；
(4) during testing and after experiment, if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements；It is trying
During testing, chair framework and its fastener is allowed to deform, condition is to test skeleton and the front profile of head rest cannot be forwards
Beyond a lateral vertical plane, to head rest, this plane passes through seat R-point, i.e. point at R points front 150mm；To seat bone
Frame part, this plane is by the point at 100mm in front of seat R points.
3. a kind of long fiber composites rear seat of passenger car skeleton original material design side according to claim 1
Method, it is characterised in that：
Derivation LFT tablet critical impact energy expression formulas described in step 2, include the following steps：
First, determining LFT tablets critical impact energy, there is power function relationships with LFT tablet fibers overall thickness：
Using the density value of glass fibre and PP matrixes, fiber quality score is scaled fiber volume fraction Vf, then be calculated
Fiber total thickness t × V of form of ownership LFT tabletsf, by critical impact energy Umin pIt is non-by formula (1) progress with fiber overall thickness
As a result linear fit is shown in logarithmic coordinates system；
Uminp=K × (t × Vf)β (1)
K and β is by the determining material parameter of experiment in formula；
Second, respectively to the residual speed and initial impact speed after the drop impact difference fiber quality score tablet of different-diameter
Degree, and nonlinear fitting is carried out using formula (2), obtain critical speed of dropping hammer；
Wherein：vrFor the rebound velocity that drops hammer, vlFor critical speed of dropping hammer, v0For initial impact speed of dropping hammer, k is fitting parameter；
Third calculates the critical speed of all tablets that fitting obtains according to formula (3), obtain difference drop hammer diameter when
The critical impact energy U of LFT tabletsmin p；
mpExpression is dropped hammer quality；
4th, the critical impact energy of the different diameters that drop hammer is subjected to nonlinear fitting using formula (4), fitting result is drawn on figure
In, obtain difference drop hammer diameter impact when, critical impact energy and fiber overall thickness logarithmic plot；
Uminp=K × (t × Vf)β (4)
In formula：K and β is by the determining material parameter of experiment, and t is slab-thickness, VfFor fiber volume fraction；
5th, formula (4) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as change certainly
Amount, shown in formula (5)：
Uminp=K × (t × Vf×Dt)β (5)
DtExpression is dropped hammer diameter；
6th：By comparing the theoretical calculation and simulation result of LFT tablet critical impact energies, critical impact energy is verified
The accuracy of theoretical expression.
4. a kind of long fiber composites rear seat of passenger car skeleton original material design side according to claim 1
Method, it is characterised in that：
Research described in step 3 is based on impact energy and requires lower LFT plate material design methods, includes the following steps：
First：Using critical impact energy as bridge, it is established that tablet energy-absorbing requires the relational expression between material parameter
(8)；
Known LFT energy absorptions analysis model is：
Acquire Umin pFor：
Wherein UimpFor drop impact energy, UabsEnergy, U are absorbed for tabletimpAnd UabsValue range be [0, Umin p]；
Formula (5) and (7), which are combined, must contact：
Then：Using formula (8) on the one hand estimation LFT tablet limit impact energys, on the other hand instruct LFT materials initial designs and
Selection：
Assuming that thickness, the fiber volume fraction of the known LFT tablets, and assume the diameter of impact body, while understanding impact body and returning
The energy-absorbing requirement of tablet, i.e. U when bulletabsIt has been determined that from right to left according to formula (8), impact body limit impact energy is calculated,
And then acquire the limit impact initial velocity of impact body；
Assuming that in the case where determining the two impact working conditions of impact energy and impact body diameter, from the angle of safety coefficient, setting
LFT tablets need the approximate range for absorbing impact energy to be calculated from left to right according to (8), obtain LFT material fiber volumes point
Several and corresponding slab-thickness, realizes the initial designs of material.
5. a kind of long fiber composites rear seat of passenger car skeleton original material design side according to claim 1
Method, it is characterised in that：
Seat back skeleton original material, including content in detail below are designed described in step 4：
Luggage case block Shock Environmental Condition is simplified, carrying out the initial of material to LFT seat back plate structures using formula (8) sets
Meter and selection；
Using single luggage block impact backboard as research object, be reduced to drop impact LFT slab constructions, define drop hammer it is straight
Diameter, quality and initial impact speed, wherein the length of side of luggage block to be considered as to the diameter to drop hammer；
Be not pierced from tablet and safety coefficient from the point of view of, calculate separately, when tablet absorbs energy Uabs, account for drop impact
LFT fiber qualities score when the ratio of energy is 100%, 90%, 80% and 70% and corresponding slab-thickness complete rear row seat
The initial designs of chair back framework.
6. a kind of long fiber composites rear seat of passenger car skeleton original material design side according to claim 1
Method, it is characterised in that：
Initial designs result finite element and experiment are verified described in step 5, are included the following steps：
(1) a kind of LFT materials of mass fraction are selected, the metal material of back seat backboard skeleton is replaced, utilizes finite element fraction
Software is analysed, the simulation model of luggage case block impact test is established, the finite element model of foundation and sled test Comparative result is tested
Demonstrate,prove the validity of LFT material models；
(2) backboard skeleton thickness is adjusted, carries out calculating the satisfactory seat back thickness value of acquisition, divide with based on energy absorption
It is close to analyse the seat back plate structure initial designs method thickness value that model carries out；It is proved with this, using energy absorption analysis model,
The feasibility and validity of original material design are carried out to LFT seat back plate structures.
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