For manual lay-up, once the prepreg materials have been thawed and the corresponding patterns cut, the release film must be released as well as the protection paper from one face of the prepreg, performing this operation with extreme care so as not to detach strands that alter their alignment or produce damages. The prepreg plies shall be placed one on top of another, fulfilling the orientations called out in the applicable drawing and minimizing the amount of air occluded below the ply.
For manual lay-up, prepregs with protection film on both sides, the ply keeping must be placed the protection film on its external face, subsequently removing it just before application of the next prepreg ply.
During the lay-up process, special attention shall be paid to prevent leaving any rest of protection film or backing paper incorporated inside the part.
Table 4. Parameters for application of release agents/mold sealers
2.4.1 First Test. Material RB 460.
The first Test was executed with Bag RB 460. The main characteristics of the RB and the piece are the followings:
Ø bag tubular 12” = 194mm = Ø inner tube
As we can see in the FIGURE 2.4.1, the piece that we are going to manufacture doesn’t have installed the release film or the breather
In the picture 2.4.2 we can see the RB460 partially installed. RB has only a part with release agent, the part in contact with de GFRP.
FIGURE 2.4.1.1 Glass fibre laminated without Bag RB 460 installed
FIGURE 2.4.1.2. Bag RB460 Installation in process
AIMS 05-010-008
Vacuum intakes Vacuum tape
After performing the complete vacuum bag, we can see that inside the tube (our hollow part is a tube) the Bag RB is completely adapted to the internal GFRP face. This is possible due to the characteristics of elongation of the RB Bag, and because the diameter of the RB Bag is litter than the internal diameter of the tube.
If we don’t adjust correctly the RB Bag to the inner face of the tube, during the cure cycle the resin of the GFRP will flow looking the GAP that we have left.
FIGURE 2.4.1.3. Vacuum applied in Bag RB460
FIGURE 2.4.1.4. wrinkles in bag RB 460 after vacuum
Retenedor of cork RB 460
The aspect of the part after cure cycle is the following:
As we can see in the picture, the aspect of the part is very good. Only there are some little excess of resin that are not a high deviation because with a little sanding it will be solved. This excess of resin, as we saw in the page previous, can be avoid if we brace well the RB Bag.
FIGURE 2.4.1.5. PART0001 demould after cure cycle.
Excess of resin AIMS 05-010-008 cure
2.4.2 Second Test. Material RB 460.
After checking that the RB bag 460 Works well, we took another test in order to compare the same part but manufactured with the process stablished with the
conventional HLU process (Bagging films, Release film, Breather and bleeder fabrics,) The main characteristics of the RB Bag and piece that we manufactured in the second proof were the followings:
Ø bag tubular 12” = 194mm = Ø inner tube Tube without curves
As we can see in the FIGURE 2.4.2.1, the Bag RB is completely adapted to the internal GFRP face of the inner tube.
FIGURE 2.4.2.1Vacuum applied in second test
In the following picture we can see the difference between the proof manufacturing using RB 460 FIGURE 2.4.2.2 and a part manufactured with the conventional HLU process FIGURE 2.4.2.3.
The deviation that we can appreciate in FIGURE 2.4.2.3 is called “Pin Holes” and the kind of rework has been indicated in Point 11 of FIGURE 1.1.3.
FIGURE 2.4.2.2. Result using RB BAG
FIGURE 2.4.2.3 Result with conventional Hand Lay Up process
FIGURE 2.4.2.3.1 Detail zoom of pin holes
AIMS 05-010-008 cure
2.4.3 First Test. Material RB 370.
After performing the first two tests with RB 460, now it is the moment to try with the RB Bag 375. Firstly, let me remind you the characteristics of this bag:
RB 375
Elongation max 500%.
Work Temperature resistance 155 ºC.
Comparing it to the previous bag, this one has a higher limit of elongation (RB 460 Elongation max 250%) but the work temperature resistance is lower (RB 460 193 ºC).
RB Bag 375 can be better for parts with a more complicated shape.
The main characteristics of the RB Bag and piece that we are going to manufacture in the second test are the following:
Ø tubular bag 12” = 194mm = Ø inner tube
Like in the cases before, the diameter of the inner tube is more or the same that the tubular bag.
Knowing that the characteristics of elongation are very high, we will realize the test in a tube with curves. The Bag RB 375, when starting to elongate, it deforms differently inside the tube due to the shape. It is very important to leave a little of excess of Bag in order to help the material in the elongation to R1 and R2.
FIGURE 2.4.3.1 Installation of Bag RB370 in process.
FIGURE 2.4.3.2 Manufacturing tool used in first Test with bag RB370
AIMS 05-10-008
Contour breather fabric
R1 and R2 are the radius of the tube. The area is indicated in blue color and has to expand the RB 375 when vacuum is applied.
After applying vacuum in our RB375 bag, the material will be elongated until arriving to R1 and R2. For this reason, it is very important to leave an excess of bag in the inner radius. In the following sketches the status of RB 375 has been simulated before and after apply vacuum.
FIGURE 2.4.3.3 Sketch simulation of inner tool with bag RB370.
FIGURE 2.4.3.3a Sketch inner simulation with Bag RB370. PRE-& POST Vacuum
PRE-Vacuum POST-Vacuum
External shape of the tooling.
A
In the following picture we can appreciate how the RB Bag has expanded until being in contact with the pre-preg glass fibre.
In the FIGURE 2.4.3.4 we can see how the RB375 has been adapted fully to the inner shape of the tool. Also we can see the exceess of Bag.
After cure cycle, we can appreciate that the RB 375 Bag has been more elongated during the curing of the Part, as we can see in the FIGURE 2.4.3.5 . We think that this has been caused due to the excess of capacity of elongation of the RB 375 bag. As we
FIGURE 2.4.3.4 View from Inside with Bag RB 370 adapted after vacuum.
FIGURE 2.4.3.3b View from A. Real picture
Excess of bag
R2
can see in the FIGURE 2.4.3.6, all the piece has excess of resin in all the inner part of the tube.
In the following FIGURE 2.4.3.6 we can appreciate how is the RB Bag has little wrinkles during the cure cycle, the resin flow and how it fills these Gaps.
Now, we are going to compare a conventional manufacturing HLU vs manufacture with RB 375. As we can see in the pictures below, the delamination doesn’t exist with RB 375 but the deviation of excess of resin exists.
FIGURE 2.4.3.5 View from Inside Tool After Cure Cycle
FIGURE 2.4.3.6 View from Inside Part After demould
Both views are from outside of the part.
2.4.4 Second Test. Material RB 370.
After seeing the problems that we have had in the first test, lets show another sample with another piece (Part004) in order to see if the problem is the excess of capacity of elongation of RB 375 Bag. The main characteristics of the RB Bag and piece that we are going to manufacture in the second test are the followings:
Ø tubular bag 12” = 194mm = Ø inner tube
Only one radius.
FIGURE 2.4.3.7 Comparison result between conventional HLU and with bag RB370.
FIGURE 2.4.4.1 Inner view for Second Test with bag RB370.
After manufacturing and curing cycle of the second test with RB 375 bag we can appreciate that we have had the same problem than in the first test. We see excess of resin induced by the elongation of the bag during the cure cycle.
2.4.5 First Test. Material RB 500.
After performing the first four tests with RB 375 & 460, we tried with the RB Bag 500.
First of all, lets me remind you the characteristics of this bag:
RB 500
Elongation max 350%.
Work Temperature resistance 260 ºC
Comparing this one to the previous two bags, this one has the limit of elongation between RB 460 and RB 375, but the work temperature resistance is the biggest (260 ºC). Although the limit of elongation is higher than the limit of RB 375 we are going to do the test with a tube without curves because we observed that the bag is too rigid.
The main characteristics of the RB Bag and piece that manufactured in the second test are the followings:
Ø tubular bag 65mm < 80mm = Ø inner tube
FIGURE 2.4.4.2 Excess of resin appear after cure cycle
In this case, the diameter of the inner tube is bigger than the tubular bag:
Although the diameter of the tubular RB500 is quite bigger than the diameter of the inner tube, after applying the vacuum the RB 500 bag have been adapted completely to the tool face as we can see in the picture POST-VACUUM.
As it is shown below this, is the best bag adapted of all the test performed.
As we can see in the pictures below, the quality of the part after cure cycle is perfect:
No excess of resin
FIGURE 2.4.5.1 Outside view of manufacturing tool and section of part drawing
View Pre-Vacuum View Post-Vacuum
FIGURE 2.4.5.2 Inner view of manufacturing tool with bag RB500 positioned (left) and bag RB500 with vacuum applied (right).
No lack of resin
No delamination appears