Lab class

School of Engineering Sciences Professor J.M. Barton, Dr A.R. Chambers Composites Engineering SESG6022

Manufacturing page 1 of 4 Laboratory Class

MANUFACTURE OF COMPOSITE LAMINATES USING AUTOCLAVE CONSOLIDATION AND RESIN INFUSION Aim: The aim of this laboratory class is to introduce students to two standard manufacturing techniques and demonstrate the operations required to produce a composite component. Introduction There are a vast number of manufacturing techniques that are used to produce composite components. In the laboratory class students will be introduced to two techniques: prepreg autoclave consolidation (representative of aircraft component manufacture) and resin infusion of dry mat (representative of ship building construction). The methods of manufacture used in the laboratory class are representative of those used in industry and follow identical steps to the industrial manufacturing process. Students will work in two groups: one group will produce the infused component, the other the prepreg component. Students will be provided with the raw materials and consumables necessary to manufacture panels 250 x 250 mm of glass reinforced plastic. The resultant prepreg and infusion glass mat materials are of an identical lay-up so that the end results will be comparable. The target of laboratory class is to produce two consolidated panels that can be cut into standard test specimens for the materials testing laboratory in the following week. During the laboratory class students should consider the possibilities of automating the process for mass production and the cost involved with the labour intensive techniques they are applying to produce the component. Students should take notes of the procedure used to make their mould and any adjustments to the procedures outlined below, that may effect the final quality. On each bench is a box of gloves please put on a pair of gloves before starting to handle the materials. Materials The target is to produce a panel with the following lay-up [-45, +45, 90, 0, 90, 0, 0, 90, 0, 90, +45, -45], i.e. 12 plies of material to produce a ‘quasi isotropic’ stack. The glass material being used in the laboratory is E-glass both pre-preg and dry fibre are 600g/m2 of glass; the dry mat is stitched, the pre-preg is lightly stitched. The resin in the prepreg is SE84LV from Gurit. It is an epoxy resin that can cure between 90oC and 120oC and has an out-life of 60 days at room temperature. The resin used for the infusion is Prime 20LV epoxy resin from Gurit. To cure at room temperature it must be mixed with a hardener. The hardener used is Prime 20 fast



hardener and is mixed with the resin in the ratio 100:26 by weight. The mix of resin and hardener is referred to as ‘resin’ as well. On the prepreg bench there are six ‘plies’ of material cut to 250 x 250 mm. The material has been removed from the freezer and defrosted. Each ply contains 2 layers of glass at [0, 90] or [+45,-45]. The plies have a backing film on one side; one is marked with an arrow to indicate the direction of the upper layer. The first step in the process is to work out how to form the above stack from the six plies. On the infusion bench there are six plies of 250 x 250 mm material. Here the plies contain 2 layers of glass stitched together to form a [0, 90] or [+45,-45] stack. It is obvious from inspection the way the fibres are orientated. The first step in this process in also to work out how these plies from a stack. There are also two pots each containing 500 g of resin and 150 g of hardener. Moulds and consumable materials To consolidate the material it is necessary to use a mould, in this case a flat plate, and encase the material in a bag that allows the material to be subjected to a vacuum pressure and facilitates resin infusion through the stack. On the prepreg bench there is a flat aluminium alloy plate, coated with a release agent ‘Frekote’ on one side. The edges of the plate have tacky tape mounted on them; this is what will be used to make the vacuum seal. Likewise on the infusion bench there is a glass plate also coated with Frekote with tacky tape mounted around the edges. The consumables for the prepreg consolidation are: peel ply (striped), release film (clear), breather (woolly) and vacuum film (purple). The peel ply draws the resin to the surface in an even layer during consolidation. The release film is perforated and non-stick, it allows a small bleed of the resin during consolidation and permits easy removal of the consumables. The breather produces an even vacuum path through the mould. The vacuum film completes a flexible mould and contains the vacuum. The consumables for the infusion are: peel ply (striped), vacuum film (purple), infusion mesh (green). There are also two lengths of spiral wrap encased in infusion mesh and two hoses. The infusion mesh distributes the mixed resin evenly over the stack and provides a permeable path for the resin. The spiral wrap allows the mixed resin to pass evenly into the entry and exit hoses. Scissors, extra tacky tape and flash tape are provided on each bench. On the prepreg bench there is a roller for de-bulking and a vacuum breach valve. On the infusion bench there is a mixing pot, spatula, a resin trap comprising a vacuum film parcel with breather and a breach valve, two clamps and a balance.



Please check you have all the consumables prior to starting the manufacturing. Production of flexible closed mould Pre-preg 1. Take first layer of prepreg and place on aluminium mould. 2. Remove protective film on other side prepreg. 3. Place second layer of prepreg on the correct side with the correct orientation and

lay on first layer with upper layer of film still in place. 4. De-bulk with roller. 5. Remove upper layer of protective film. 6. Repeat steps 3-5 orientating the prepreg to make the required stack. 7. Put peel ply on stack: stripes should be parallel to the 0o plies. 8. Put release film on peel ply and secure to mould with flash tape. 9. Put breather in position. 10. Make provision for pleats in the vacuum bag with the tacky tape. 11. Position breach valve on plate with an extra layer of breather and release film. 12. Attach vacuum film to tacky tape on three sides. 13. Make vacuum connection in the bag. 14. Seal last side of the bag. 15. Check for leaks. Infusion 1. Stack the dry mats in the required orientation. 2. Place on glass plate so that the 0o ply is parallel with the infusion direction 3. Cover in peel ply: stripes should be parallel to the 0o ply. 4. Cover in infusion mesh. 5. Position spiral wrap at each end of the mould. 6. Fix hoses to spiral wrap and secure to mould with extra tacky tape. 7. Make provision for pleats in the vacuum bag. 8. Make the vacuum bag and attach hose to resin trap. 9. Check for leaks. Manufacture Prepreg Take the mould to the autoclave, attach to vacuum pump and set appropriate cure cycle for 120oC and an applied pressure of three bar for 45 minutes. Infusion



1. Measure 400 g of resin into the empty mixing pot using the balance as a check. 2. Slowly pour at correct amount of hardener into the pot remember the ratio

mentioned earlier. 3. Mix the resin and hardener with a spatula. 4. Put the pot with the resin and hardener on the stool so that it is below the bench. 5. Insert hose. 6. Switch on vacuum pump. 7. Watch the resin flow though the material and into the trap. 8. Once the resin is in the trap, try to balance the flow using the regulator valve. 9. Clamp off resin end. 10. Maintain vacuum. De-bagging After curing both groups should make arrangements with the demonstrators/technicians to de-bag their plate later in the week and see the consolidated panel prior to cutting. A visual inspection at this stage should allow a rudimentary assessment of quality.

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