Patent Publication Number: US-2022219442-A1

Title: A method of manufacturing bonding structural test block with defects

Description:
RELATED APPLICATION 
     The application is based upon and claims priority to Chinese Patent Application No. 202010507968.9, filed on Jun. 5, 2020, the entire contents of all of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of nondestructive detection, in particular to a method of manufacturing a bonding structural test block with defects. 
     BACKGROUND 
     With the rapid development of civil aviation, it is required that the aircraft structural materials must develop in the direction of low density, high strength, high toughness, high temperature resistance and corrosion resistance. In the traditional civil aviation structure, it is necessary to connect parts by a large number of rivets to form some parts. Small aircraft usually includes tens of thousands of rivets, which inevitably makes the aircraft weight heavier. The cementing structure has been widely applied to the civil aircraft structure instead of riveting, but it is inevitable to introduce various defects in the manufacturing process of the cementing structure, including crack, gap/hole, debonding, weak bond, etc. 
     Kiss-bonds is a defect type in the cementing structure and refers to a defect that two surfaces in the cementing structure are in close contact, that is, the two surfaces are not bonded, and the kiss-bonds will lead to the reduction of the structural load capacity. In addition, the defect similar to that of the kiss-bonds is weak bond, that is, two surfaces are bonded incompletely. Due to some structural continuity, the weak bond may be more difficult to evaluate. The kiss-bonds and weak bond defects may occur in monolithic, sandwich, bonded or repaired composite materials, which may be introduced in the manufacturing process and may also be caused by insufficient damage or repair. The loss of the structural strength and the potential growth of defects (that is, growing from weak bond/kiss-bonds to debonding) under the loading condition during use make the detection and evaluation of the defect type particularly important. 
     In order to test the defects, a comparison test block with defects must be created first. However, it is difficult to manufacture the test block, so it is very important to controllably manufacture the test blocks with kiss-bonds and weak bond and detect the internal defects. 
     SUMMARY 
     The present disclosure provides a method of manufacturing a bonding structural test block with defects, including the following steps: 
     providing a first plate and a second plate; 
     applying an adhesive on an upper surface of the first plate to form an adhesive layer; 
     heating and curing at least partial region of the adhesive layer for the first time; 
     placing the second plate on the adhesive layer: and 
     heating and curing the adhesive layer for the second time to form a bonding structural test block. 
     In some embodiments, the at least partial region includes a plurality of preset region blocks which are distributed on the adhesive layer at intervals: and the step of heating and curing the at least partial region of the adhesive layer for the first time includes: alone heating and curing the plurality of preset region blocks of the adhesive layer. 
     In some embodiments, the method further includes: determining positions and area of the plurality of preset region blocks according to preset positions and preset area of defects before the step of alone heating and curing the plurality of preset region blocks of the adhesive layer. 
     In some embodiments, the step of alone heating and curing the plurality of preset region blocks of the adhesive layer is performed by a pre-curing equipment, the pre-curing equipment includes a heating plate and a plurality of heating columns movably arranged on heating plate, and the positions of the plurality of heating columns are adjusted to correspond to the plurality of preset region blocks on the adhesive layer. 
     In some embodiments, the step of applying the adhesive on the upper surface of the first plate to form the adhesive layer includes: applying an adhesive on a region close to an end part of the upper surface of the first plate to overlap the second plate on an end of the first plate. 
     In some embodiments, the method further includes: performing temperature rise rheological property test on the adhesive and obtaining a rheological curve of the adhesive, and selecting the temperature of the heating and curing for the first time and the temperature of the heating and curing for the second time according to the rheological curve. 
     In some embodiments, the step of applying the adhesive on the upper surface of the first plate to form the adhesive layer includes: applying the adhesive on the entire region of the upper surface of the first plate to make the adhesive cover the upper surface of the first plate. At least partial region includes the entire region of the adhesive layer. The manufacturing method further includes: before heating and curing the entire region of the adhesive layer for the first time, applying and pasting the second plate on the adhesive layer and then heating and curing the adhesive layer for the first time; after the entire region of the adhesive layer is heated and cured for the first time, separating the first plate and the second plate from the middle of the adhesive layer, superposing the separated first plate and second plate, and heating and curing the adhesive layer for the second time. 
     In some embodiments, both the heating and curing the adhesive layer for the first time and the second time is performed by an autoclave; and the temperature of the heating and curing the adhesive layer for the first time and for the second time is same and the heating time of the heating and curing the adhesive layer ( 3 ) for the first time and for the second time is different. 
     In some embodiments, the method further includes: creating a crack on the adhesive layer. 
     In some embodiments, the adhesive is an adhesive film, and the adhesive film is paved on the upper surface of the first plate to form the adhesive layer. 
     In some embodiments, the first plate and the second plate which are made of composite materials are provided, and the composite material of the first plate and the composite material of the second plate are the same or different. 
     in some embodiments, after the test block is obtained, the test block is subjected to ultrasonic scanning to determine defect information. 
     Based on the technical solution provided by the present disclosure, the method of manufacturing the bonding structural test block with defects includes: providing a first plate and a second plate; applying an adhesive on an upper surface of the first plate to form an adhesive layer; heating and curing at least partial region of the adhesive layer for the first time; placing the second plate on the adhesive layer; and heating and curing the adhesive layer for the second time to form a cementing structure test block. According to the present disclosure, the at least partial region of the adhesive layer is heated and cured for the first time and chemical reaction occurs, so that the at least partial region forms a defect, and controllable manufacturing of the defect is realized. The test block with defects is subjected to mechanical detection to simulate the actual defective product. Furthermore, according to the method provided by the present disclosure, weak bond defect and kiss-bonds defect with different bonding strength are simulated by controlling the percentage of the at least partial region in the entire region of the adhesive layer. 
     Other features and advantages of the present disclosure will become apparent by the detailed destinations for exemplary embodiments of the present disclosure with reference to the following accompany drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To describe the technical solutions in the embodiments of the present disclosure or in the prior art more clearly, the following briefly describes the accompanying drawings required for describing the embodiments or the prior art. Apparently, the accompanying drawings in the following described accompanying drawings show some embodiments recorded in the present disclosure, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings. 
         FIG. 1  is a schematic diagram of steps of a method of manufacturing a bonding structural test block with defects according to an embodiment of the present disclosure; 
         FIG. 2  is a rheological curve of an adhesive film according to an embodiment of the present disclosure; 
         FIG. 3  is a structural schematic diagram of pre curing equipment used by an embodiment of the present disclosure; 
         FIG. 4  to  FIG. 7  are schematic diagrams of process steps of a test block with weak bond defect manufactured by an embodiment of the present disclosure, wherein  FIG. 4  shows performing first heating and curing on the adhesive layer by the pre-curing equipment,  FIG. 5  shows overlapping the second plate on the first plate,  FIG. 6  shows an enlarged structure diagram of the adhesive layer in  FIG. 5 , and  FIG. 7  shows a structural schematic diagram of a test block with defects formed after the second heating and curing; and 
         FIG. 8  to  FIG. 10  are schematic diagrams of process steps of a test block with kiss-bonds defect manufactured by an embodiment of the present disclosure, wherein  FIG. 8  shows superposing the first plate, the adhesive layer and the second plate,  FIG. 9  shows separating the first plate and the second plate of an intermediate cementing structure subjected to the first heating and curing, and  FIG. 10  shows a structural schematic diagram of a test block with defect formed after the second heating and curing. 
     
    
    
     DETAILED DESCRIPTION 
     To make the objectives, technical solutions, and advantages of the present disclosure clearer, a manufacturing method of a cementing structure defect test block provided by the present disclosure is further described below in detail through the embodiments and with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining the present disclosure, rather than for limiting the present disclosure. 
     As shown in  FIG. 1 , a method of manufacturing a bonding structural test block with defects according to an embodiment of the present disclosure includes the following steps: 
     Step  101 : a first plate  1  and a second plate  2  are provided; 
     Step  102 : an adhesive is applied on an upper surface of the first plate  1  to form an adhesive layer  3 ; 
     Step  103 : at least partial region of the adhesive layer  3  is heated and cured for the first time; 
     Step  104 : the second plate  2  is placed on the adhesive layer  3 ; and 
     Step  105 : the adhesive layer  3  is heated and cured for the second time to form a bonding structural test block. 
     According to the embodiment of the present disclosure, the at least partial region of the adhesive layer  3  is heated and cured for the first time and chemical reaction occurs, so that the at least partial region forms a defect, and controllable manufacturing of the defect is realized. The test block with the defect is subjected to mechanical detection to simulate the actual defective product. Furthermore, according to the manufacturing method provided by the present disclosure, weak bond defect with different bonding strength is simulated by controlling the percentage of the at least partial region in the entire region of the adhesive layer. 
     It should be noted herein that other steps may be performed among the above steps. 
     Referring to  FIG. 6 ,  FIG. 6  is a structure diagram of the adhesive layer  3  after the first heating and curing, wherein  31  is a non-curing region, and  32  is a curing region. Before the cementing structure defect test block is manufactured, preset positions and preset area of defects of a test block with defects to be manufactured are determined first. The method of this embodiment further includes: positions and area of the plurality of preset region blocks are determined according to the preset positions and preset area of the defects before the step of alone heating the plurality of preset region blocks of the adhesive layer. that is, a preset region block is a curing region. 
     In one embodiment, the embodiment of the present disclosure provides a manufacturing method of a weak bond defect test block. As shown in  FIG. 4 , the at least partial region of the embodiment includes a plurality of preset region blocks which are distributed on the adhesive layer  3  at intervals; and the step of heating and curing the at least partial region of the adhesive layer  3  for the first time includes: the plurality of preset region blocks of the adhesive layer  3  are independently heated. 
     Specifically, in this embodiment, the plurality of preset regions of the adhesive layer  3  are independently heated by pre-curing equipment  5  shown in  FIG. 3 . The pre-curing equipment  5  includes a heating plate  51  and a plurality of heating columns  52  which are movably arranged on the heating plate  51 , and the positions of the plurality of heating columns  52  are adjusted to correspond to the plurality of preset regions on the adhesive layer  3 . 
     In order to be suitable for manufacturing of test blocks with different defect sizes and positions, the pre-curing equipment  5  of this embodiment further includes a positioning groove  53 , the heating column  52  is arranged in the positioning groove  53 , and the position of the positioning groove  53  is adjusted to change the position of each of the heating columns  52 . 
     As shown in  FIG. 4 , the plurality of heating columns  52  abut against the adhesive layer  3  to heat and cure the plurality of preset regions of the adhesive layer  3  for the first time, and the adhesive layer  3  after the first heating and curing is shown in  FIG. 6 . 
     As shown in  FIG. 7 , the step of applying the adhesive on the upper surface of the first plate  1  to form the adhesive layer  3  includes: the adhesive layer  3  is formed on a region, close to the end part, of the upper surface of the first plate  1 , and the second plate  2  overlaps the first plate  1 . 
     As shown in  FIG. 2 . the method of this embodiment further includes: the adhesive is subjected to temperature rise rheological property test and a rheological curve of the adhesive is obtained, and the temperature of the first heating and curing and the temperature of second heating and curing are selected according to the rheological curve. 
     Specifically, the temperature of the first heating and curing is less than the temperature of the second heating and curing. 
     The method of manufacturing the test block with weak bond defect is described below in detail with reference to the specific embodiments. 
     Firstly, materials of the first plate  1 , the second plate  2  and the adhesive film are selected. In this embodiment, the composite material of the first plate  1  and the composite material of the second plate  2  are the same and are CYCOM X850, and the material of the adhesive film is PL7000. 
     The adhesive film is subjected to temperature rise rheological property test by a rheometer. During the test, a parallel plate clamp is used, the adhesive film is made into a wafer with a diameter of 25 mm at room temperature, three adhesive films are superposed and compacted to prepare a test sample, and the rheological curve of the adhesive films is obtained, as shown in  FIG. 2 . 
     as shown in  FIG. 4 , the first plate  1  is applied and pasted, and the adhesive film is applied and pasted on the surface of the first plate  1 . 
     The heating column  51  in the pre-curing equipment  5  is adjusted according to the preset position and preset area of the designed weak bond defect and is connected to the upper surface of the adhesive film. Specifically, in this embodiment, fifty needle-like heating columns are arranged, and each of the heating columns  51  is round with a diameter of 0.2 mm. 
     The adhesive film is partially pre-cured by the pre-curing equipment  5 , the heating rate of the adhesive film in contact with the heating columns  51  on the adhesive film is 2-3° C./min, the curing temperature is 100° C.±10° C., and the time is 30 min. 
     As shown in  FIG. 5 , the pre-curing equipment  5  is removed, and pavement of the second plate  2  on the adhesive film is completed to obtain a single-overlapping cementing structure. 
     Peelable cloth, an isolating film, ventilated felt and a pressure-equalizing plate auxiliary material are sequentially placed on the applied single-overlapping cementing structure, the test block is packaged by a vacuum bag and is put into an autoclave for curing, wherein the curing temperature is 180° C., heat preservation is conducted for 120 min, and the curing pressure is 0.7 Mpa. 
     Demolding is performed to obtain the single-overlapping test block with partial weak bond as shown in  FIG. 7 . 
     The test block is subjected to ultrasonic scanning to obtain a defect signal. Machining is performed to obtain a single-overlapping test block meeting the standard. 
     The single-overlapping test block is subjected to mechanical property test. 
     In another embodiment, the present disclosure provides a method of manufacturing a test block with kiss-bonds defect. As shown in  FIG. 8 , the adhesive layer  3  covers the upper surface of the first plate  1 . At least partial region includes the entire region of the adhesive layer  3 . The manufacturing method further includes: before the entire region of the adhesive layer  3  is heated and cured for the first time, the second plate  2  is applied and pasted on the adhesive layer  3  and then the adhesive layer  3  is heated and cured for the first time; after the entire region of the adhesive layer  3  is heated and cured for the first time, as shown in  FIG. 9 , the first plate  1  and the second plate  2  are separated from the middle of the adhesive layer  3 , the separated first cementing  1  and second plate  2  are superposed ( FIG. 10  shows that the separated first plate  1  and second plate  2  are superposed), and the entire cementing structure is heated and cured to heat and cure the adhesive layer  3  for the second time. 
     As shown in  FIG. 9 , the first plate  1  and the second plate  2  are separated from the middle of the adhesive layer  3 , and at this time, an adhesive layer split body  3   a  is arranged on the upper surface of the first plate  1  and an adhesive layer split body  3   b  is arranged on the lower surface of the second plate  2 . 
     In this embodiment, both the first heating and curing and the second heating and curing adopt an autoclave for heating and curing; and the first heating and curing and the second heating and curing have the same temperature and different heating time. 
     In the above embodiments, a crack may be preset on the adhesive layer  3  according to the setting requirement of the defect. 
     In order to facilitate the formation of the adhesive layer  3 , the adhesive of this embodiment is an adhesive film, and the adhesive film is applied on the upper surface of the first plate to form the adhesive layer  3 . 
     The manufacturing method of this embodiment provides a first plate  1  and a second plate  2  which are made of composite materials, wherein the composite material of the first plate  1  and the composite material of the second plate  2  are the same or different. 
     After the test block is obtained, the test block is subjected to ultrasonic scanning to determine defect information. 
     The method of manufacturing the test block with kiss-bonds defect is described below in detail with reference to the specific embodiments. 
     The first plate  1 , the second plate  2  and the adhesive film are prepared first. In this embodiment, the composite material of the first plate  1  and the composite material of the second plate  2  are the same and are CYCOM 970/PWC T300 3K ST (CCF), and the material of the adhesive film is PL7000. 
     as shown in  FIG. 8 , the crack  33  is preset on the adhesive film, the first plate  1 , the adhesive film and the second plate  2  are sequentially applied to form an intermediate cementing structure, peelable cloth, an isolating film, ventilated felt and a pressure-equalizing plate auxiliary material are sequentially placed above the intermediate cementing structure, and the intermediate cementing structure is packaged by a vacuum bag and is put into the autoclave for the first heating and curing, wherein the curing temperature is 177° C.±10° C., heat preservation is performed for 120 min, and the curing pressure is 0.7 Mpa. 
     As shown in  FIG. 9 , the first plate  1  and the second plate  2  are separated by an external force, and the first plate  1  and the second plate  2  are separated from the middle of the adhesive layer  3 . 
     as shown in  FIG. 10 , ( FIG. 10  does not show the adhesive layer, but includes the adhesive layer), the separated first plate  1  and second plate  2  are superposed and are heated and cured for the second time, wherein the curing temperature is 177° C.±10° C., heat preservation is performed for 60 min, and the curing pressure is 0.7 Mpa; and demolding is performed to obtain the test block containing the precrack and the kiss-bonds defect. 
     It should be noted that when a component is referred to as being “fixed” to another component, the component may be directly arranged on another component or a central component may be present. When one component is considered as being “connected” to another component, the component may be directly connected to another component or a central component may be present at the same time. On the contrary, when the component is referred to as being “directly on” another component, there is no intermediate component. The terms “vertical”, “horizontal”, “left”, and “right” and similar expressions used herein are for illustrative purposes only. 
     In the description of the present disclosure, terms “first” and “second” are merely for a descriptive purpose, but cannot be understood as indicating or implying relative importance. 
     Meanwhile, the terms such as “upper”, “lower”, “left”, “right”, “middle” and “one” quoted in this specification are only convenient for clear description and are not used to limit the implementable scope of the present disclosure. The change or adjustment of the relative relationship should be regarded as the implementable scope of the present disclosure without substantial change of the technical content. 
     The foregoing embodiments are merely illustrative of several embodiments of the present disclosure, and the description thereof is more specific and detailed, but should not be construed as limiting the patent scope of the present disclosure. It should be pointed out that several variations and improvements may be made by those of ordinary skill in the art without departing from the conception of the present disclosure, but such variations and improvements should fall within the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure should be subject to the appended claims.