CN100443890C - LCM process DC resistance real-time monitoring method - Google Patents

Abstract

The present invention relates to an LCM process DC resistance real-time monitoring method. Activation conducting lines and induction conducting lines are arranged on the upper and the lower surfaces of a pre-formed body in cross way, and monitoring points are determined. DC voltage is impressed on both sides of each monitoring point, a resistance of the pre-formed body of the measured monitoring point is connected with a reference resistance in series, a divider circuit is formed, the voltage of both ends of the reference resistance is monitored, the voltage of both ends of the reference resistance is collected to a PC in real time and is displayed through conveying discharge and AD conversion, and the resistance of the measured pre-formed body is obtained through calculation. Resin mould filling process is carried out, and in the mould filling process, in order to monitor the abrupt change of the value of the voltage and judge the arrival of the flowing head of resin, all the monitoring points are in circular scan. After the mould filling process, the resistance of the pre-formed body of each monitoring point is increased, the changes of the resistance of the pre-formed body are monitored, and the situation of solidifying the resin can be known in the real time through monitoring process. The LCM process DC resistance real-time monitoring method can accurately reflect the arrival of the flowing head of the resin on each monitoring point and solidification process after the arrival and provide basis for reducing the defects of incomplete mould filling process, dry spot, etc. The LCM process DC resistance real-time monitoring method lowers rejection rate, enhances the quality of products and effectively solves the problem of the unstable quality of the products existing in the production of resin matrix composite materials.

Description

LCM technology dc resistance method method of real-time

Technical field

The present invention relates to the method for real-time of a kind of composite liquid moulding process LCM.

Background technology

Composite liquid moulding process LCM (Liquid Composites Molding) is meant the special liquid low viscosity resin under certain pressure, the injected lay in advance closed mould cavity of fibre reinforced materials or the resin molding in the heat fused die cavity, resin flows, a kind of advanced composite material process of soaking into reinforcing material and curing molding, it is extensive day by day in sector applications such as field of aerospace, automobile, shipbuilding, buildings.LCM technology is a kind of process of one-step shaping, and advantage is a flexible operation, and designability is strong, and equipment and technology cost are lower, also can not pollute environment basically.Because the component quality of this explained hereafter depends on resin flow mold filling process and chemical curing reaction thereof to a great extent, also there is distinct disadvantage LCM technology in self: long as the resin flows time, the improper substandard products that are easy to out of mould and technological design, form typical defects such as dry spot and bubble, have a strong impact on outward appearance and component quality.

At present solving the in-problem method of LCM technology is that technology is carried out Computer Simulation Optimization, but simulation can not entirely accurate reflection process condition, and effective method is that resin flows and solidification process are monitored in real time.Process-monitor can reflect state of arts in real time accurately, is convenient to timely adjusting process condition, and the rate of reducing the number of rejects and seconds is to greatest extent improved the quality of products, and provides reliable data for the research resin soaks into preform.Existing LCM process-monitor technology can be divided into non-embedded and embedded two kinds.Non-embedded monitoring method comprises ultrasonic monitoring, thermography and shooting etc., generally can technological process not impacted, but needs quite expensive monitoring equipment; Embedded monitoring technology has: be the heat monitoring of monitoring element with the thermopair, be pressure monitoring, fiber-optic monitoring technology, direct current monitoring and the dielectric monitoring technology etc. of medium with the pressure transducer.Embedded element more or less influences resin flows and component quality, but they have the advantage of accurate conveying member internal information.

U.S. ARL (Army Research Laboratory) in 1993 and Delaware university successfully develop SMART weave mobile monitoring sensor-based system and patent, Walsh Shawn M.In-situsensor method and deviCe.US5210499,1993.This technology is a pre-buried orthogonal network of conductors in die cavity, each node of network is a sensing point, adopt dielectric field to introduce movably ion, when resin forms the closed path loop when laterally the bridging of " yarn " lead is connected, these nodes will feed back the flow state in the die cavity, can infer thermal gradient and solid state according to the variation of conductivity, reach the purpose of real-time monitoring.SMART weave system has been used to monitor large-scale component resin flows forward's propelling and technology controlling and process information is provided.But there are two bigger defectives in this system, the one, and preform inside conductor pre-buried quite consuming time; The 2nd, the flow front and the curing information at node place only can be provided.Its data processing software also has certain limitation, as not describing the situation of change of output voltage in the mold filling process, DC monitoring output information and LCM analog information can not effectively be contrasted.Therefore, this technology generally only is used for large-scale, expensive parts.

Based on this DC measurement technology linear direct current motor (LDC) monitoring system that grown up again, it and SMART weave monitoring system are similar, all adopt the space between two transport elements of resin bridge joint to form closed circuit.But the transport element of LDC monitoring system is made up of two leads that are parallel to each other, and after lead was covered by resin, the output impedance or the changes in capacitance that detect between two leads can be surveyed the flow front position.The LDC monitoring system can be monitored the flow front on the whole length direction of lead, has reduced the number of lead, can obtain continuous flowing information, is specially adapted to monitor the simple technology of nowed forming.The major defect of LDC sensing technology is the check and correction of resistivity.The resistivity of resin is degree of being parallel to each other, resin kind and the function of time of two leads, and must guaranteeing to be parallel to each other two leads when mounted, could to keep resistivity be constant.Especially for the lead at vertical flow front and band angle of inclination, be difficult to accurately determine the response of sensor.This class technical development does not propose best using method so far as yet and problem such as how to arrange in mould, also is in the research and development.

Domestic more at the real-time study on monitoring of LCM technology be to adopt optical fiber sensing technology, as intensity modulation type and fiber-optic grating sensor.Lee's cinnabar, fine strain of millet Ji, Zhang Boming, Wang Dianfu, Fibre Optical Sensor monitoring composite material solidification forming process, Tsing-Hua University's journal (natural section version), 2002,42 (2): 161-164.; Wu Zhanjun, Zhang Boming etc., based on the composite material solidification on-line monitoring research of variations in refractive index, the compound substance journal, 2002,19 (6): 87-91 research is promptly to be to adopt optical fiber sensing technology to carry out LCM technology to monitor in real time.

The ultimate principle of intensity modulation type Fibre Optical Sensor is to utilize the disturbance of outer signals to change light intensity in the optical fiber, realizes the measurement of signal to external world by the variation of measuring output intensity again.This class sensor is easy to use, durable, cost is low and demodulation is accurate, and variable refractivity type, fluorescent effect type, transparency type, microbending loss type isocandela modulation technique have been used for measuring the viscosity and the space of liquid.The ultimate principle of fiber-optic grating sensor is the variation that will cause grating cycle or fiber core refractive index when the physical quantity of fiber grating environment of living in changes, catoptrical wavelength is changed, by measuring the situation of change that the variation that changes front and back reflected light wavelength obtains measured physical quantity.The kind of fiber grating is a lot, mainly is divided into: short-period grating (FBG) and long-period gratings (LPG).When coupling took place two transmission modes in fiber grating, FBG was coupled to the guided mode energy of forward transmitted in the reverse guided mode, and LPG is coupled to the guided mode of energy from forward transmitted the cladding mode, formed a plurality of absorption peaks in its transmission.

Optical fiber sensing technology has advantage a series of uniquenesses, that other sensing technologies are difficult to compare, as carrying out multiple monitoring, measuring multiple physical quantity, optical fiber light weight, volume are little, be convenient in the embedded structure, highly sensitive, be not subjected to electromagnetism, radio frequency interference etc., but it also has some inevitable defectives, for compound substance, the Fibre Optical Sensor of imbedding has been because of the local train field of disturbing optical fiber-basal body interface has influenced the integrality of compound substance main member, causes that stress concentrates the performance that may reduce structure.The great majority experiment shows, 125 μ m or more the optical fiber of minor diameter to not significantly influence such as the derogatory behaviour of compound substance, pulling strengrth, Poisson ratio, but the compression strenght to compound substance has a significant effect, and strength degradation is about 24～60%, to tangible influence is also arranged fatigue lifetime.Therefore, the real-time monitoring of adopting optical fiber sensing technology to carry out LCM is restricted.

Summary of the invention

Technology of the present invention is dealt with problems: overcomes the deficiencies in the prior art, provides a kind of and can monitor in real time, monitor accurately, and LCM technology dc resistance method method of real-time simple to operate, that cost is low

Technical solution of the present invention: LCM technology dc resistance method method of real-time, its characteristics are to realize through the following steps:

(1) size according to scantling excites lead and sensor wire to determine the monitoring point in the discharging of preform upper and lower surface intersection, and these monitoring points promptly constitute tested preform resistance;

(2) apply DC voltage in tested preform resistance both sides, and be reference resistance that size is mated mutually of this tested preform resistance series connection, constitute bleeder circuit, measure the voltage at reference resistance two ends, this voltage is collected on the PC in real time through amplifier and AD conversion to be shown, promptly obtains tested preform resistance by calculating;

(3) carry out the resin mold filling, the arrival of resin flow fronts is judged in all monitoring points of scan round during mold filling with the sudden change of monitoring voltage value; After mold filling finished, the preform resistance at each place, monitoring point was measured these preform changes in resistance all increasing, and promptly can understand the curing situation of resin in real time by monitoring.

The present invention's advantage compared with prior art is: the present invention can reflect the resin flows forward's of place, monitoring point arrival and solidification process afterwards exactly, thereby instruct process optimization, reduce mold filling not exclusively or defective such as dry spot, the rate of reducing the number of rejects and seconds, improve the quality of products, effectively solve the problem of the unstable product quality that exists in the production of polymer matrix composites.

Description of drawings

Fig. 1 is the principle schematic of the inventive method;

Fig. 2 is a preform wiring synoptic diagram of the present invention;

Fig. 3 is for realizing the monitoring system block diagram of the inventive method.

Embodiment

As shown in Figure 1, 2, concrete steps of the present invention are as follows:

(1) according to the size of member in the crisscross wiring of upper and lower surface, the upper surface discharging excites lead, lower surface discharging sensor wire, the point of crossing that each excites lead and sensor wire is the monitoring point, its resistance value R _xBe place, preform monitoring point resistance, the monitoring point should be evenly distributed on the whole surface of member, so that mold filling process is totally monitored; Also find out the point that defective workmanship may occur by processing simulation, with it as the monitoring point.

(2) be reference resistance R of preform monitoring point series connection _c, R _cThe value choosing method be: at first by repetition test the preform resistance R _xValue roughly measure, select again and R _xIn the same order of magnitude or the reference resistance R that is complementary _c, R among the present invention _cValue is 10 ¹⁰-10 ¹¹The ohmage magnitude is again at R _cAnd R _xTwo resistance in series two ends add DC voltage U _d, this voltage must experimentize to determine added DC voltage U before detection _dValue can make the preform monitoring value of electrical signals of having soaked into resin about 200, get final product U _InIt is the reference resistance R _cThe DC voltage of being got, U _InBy amplifier output back is U _Out, U _OutAfter A/D conversion, be transferred to and show in real time on the PC and store.

According to the ultimate principle of bleeder circuit, as shown in Figure 1,

$U_{\mathrm{in}}=\frac{R_x}{R_x+R_c}\·U_d---\left(1\right)$

U _out＝n·U _in(2)

$U_{\mathrm{out}}=\frac{5V}{2^8}\mathrm{DATA}\≈\frac{\mathrm{DATA}}{51}---\left(3\right)$

Wherein n is an enlargement factor, and DATA is U _OutThe data that on PC after the AD conversion, collect in real time, 5V is the reference voltage of A/D conversion chip, 2 ⁸Represent that chip used is 8 A/D conversions.

In conjunction with (1), (2) and (3) formula, obtain:

$U_{\mathrm{in}}=\frac{\mathrm{DATA}}{51n}=\frac{R_x\·U_d}{R_x+R_c}---\left(4\right)$

By the electric signal DATA that is gathered, can find the solution the preform resistance value at place, monitoring point of arbitrary moment according to following formula

$R_x=(\frac{51\·n\·U_d}{\mathrm{DATA}}-1)R_c---\left(5\right)$

(3) carry out the resin mold filling, the arrival of resin flow fronts is judged in all monitoring points of scan round during mold filling with the sudden change of monitoring voltage value; After mold filling finishes, the preform resistance R at each place, monitoring point _xAll, measure these preform resistance R increasing _xVariation, promptly can understand the curing situation of resin in real time by monitoring.

As shown in Figure 3, the monitoring system that realizes the inventive method is by the arranging of preform, reference resistance R _c, output voltage controller, amplifier and A/D converter, control circuit CPU and PC etc., the 1-16 bar can be set excites lead and sensor wire up and down in the present invention, therefore can constitute 1-256 monitoring point, control circuit CPU makes output voltage controller select 1-256 one or more in putting by control signal, passes through simultaneously and the reference resistance R _cAfter the serial connection, apply DC voltage, after this voltage process amplifier amplification and the A/D conversion, control circuit CPU scan round is also gathered the monitor signal of 1-256 monitoring point, system is provided with the A/D modular converter respectively for each bar voltage sense line, the data-switching transmission speed is very high, and all 256 monitoring point scan rounds were once only needed for 1 second.

Control circuit CPU has the Control Circulation scan function, and during monitoring, it carries out scan round to 256 tunnel monitoring routes, and for the route that does not insert, monitor signal will be shown as zero.

Claims (3)

1, composite liquid moulding LCM technology dc resistance method method of real-time is characterized in that realizing through the following steps:

(1) size according to scantling excites lead and sensor wire to determine the monitoring point in the discharging of preform upper and lower surface intersection, and these monitoring points promptly constitute tested preform resistance;

(2) apply DC voltage in tested preform resistance both sides, and be reference resistance that size is mated mutually of this tested preform resistance series connection, constitute bleeder circuit, measure the voltage at reference resistance two ends, this voltage is collected on the PC in real time through amplifier and AD conversion to be shown, promptly obtains tested preform resistance by calculating;

(3) carry out the resin mold filling, the arrival of resin flow fronts is judged in all monitoring points of scan round during mold filling with the sudden change of monitoring voltage value; After mold filling finished, the preform resistance at each place, monitoring point was measured these preform changes in resistance all increasing, and promptly can understand the curing situation of resin in real time by monitoring.

2, LCM technology dc resistance method method of real-time according to claim 1 is characterized in that: described reference resistance R _cValue is 10 ¹⁰-10 ¹¹Ohm.

3, LCM technology dc resistance method method of real-time according to claim 1 is characterized in that: described monitoring point is 1-256.

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