PROCESS GUIDE LINES: LAYUP AND CURE OF EPOXY PREPREG Easycure E-710 AND Easycure E-710FR MATERIALS 160-250 F CURING OVEN/VACUUM PROCESS
TABLE OF CONTENTS 1 Mold Preparation... 3 2 Cutting and Lay-up... 3 3 Debulk Procedure... 3 4 Bagging Procedure... 4 4.1 Recommended Shop Supplies... 6 5 Cure Cycle... 7 6 Bag Removal and Part Identification... 8
1 Mold Preparation Each mold or lay-up surface shall be cleaned prior to lay-up, using non-contaminating cleaners, such as acetone or alcohol. Mold preparation shall be performed outside the lay-up room. After cleaning, each mold shall be treated with non-contaminating release agents in accordance with the supplier s instructions. Thermocouple quantity and location will be specified on the shop traveler. 2 Cutting and Lay-up The cutting and lay-up area shall be kept free of contaminants. If prepreg laminations are pre-cut and grouped into kits for future lay-up and cure, the poly-film backing provided by PACM shall not be removed until each ply is ready to be placed in the lay-up mold. Kits shall be stored in sealed, moisture-proof containers until ready for lay-up. Upon removal from storage, the prepreg materials shall be allowed to warm to room temperature inside the sealed moisture-proof bag for at least 3 1/2 hours or until visible moisture has vanished from the outside of the bag. Any peel ply requirements will be specified on the drawing and/or shop traveler. Unless otherwise specified on the drawing, splices are allowed. However, they must overlap by at least one inch and no two splices in a single ply shall be closer together than 24 inches. Minimum distance between splices in adjacent plies is six inches. Butt splices are generally to be avoided. If butt splices are used, the maximum gap at any point is 0.030 inches. Butt splices shall have one additional ply of material, the same as the base laminate, extending for at least one inch on either side of the splice joint. White, lint-free cotton gloves are required for hand / personal protection. Talc-free latex or nitrile gloves are acceptable alternates. No cutting of prepreg materials is permitted on the tool. 3 Debulk Procedure Debulking shall be performed in order to achieve appropriate compaction. Debulking shall be performed on the first ply and than additional debulks should be performed every two (2) plies of prepreg with FAW of 500-900g/m 2 or every three (3) plies of prepreg of FAW of 300-500g/m 2 or every five (5) plies of prepreg with FAW 100-300g/m 2. a. Apply one layer of non-porous release fabric over the prepreg lay-up.
b. Apply one layer of 340g/m 2 (10oz/yd 2 ) breather (N10 or two layers of N4) on top of the non-porous release film. If the breather is not contaminated with resin or other foreign material, the breather may be re-used. c. Install nylon bagging film over the laminate or form-fit a silicone rubber bag and edge seal to the tool with vacuum bag sealant; install the vacuum connector through the bag. Use multiple vacuum connectors so that no point on the part is more than 60 inches from a vacuum source. Note: Install the vacuum connectors on the tool surface outside the perimeter of the laminate wherever possible. Placing the connector in a bag pleat is an acceptable alternate. In case that the mold is not big enough to accommodate this type of arrangement you can place the vacuum port on top of the part by folding the bag and use 4-6 plies of breather. d. Apply vacuum of at least 25 inches Hg for at least 15 minutes at a rate that does not cause the prepreg to shift. When specified by the applicable shop traveler, the laminate may be heated to 100 F maximum and held for 10-15 minutes during vacuum application but there shall be no more than six (6) debulks at 100 F on any lay-up. The final debulk shall be for 30 minutes minimum. 4 Bagging Procedure The shop traveler will give specific instructions regarding the use of peel plies, bleeder materials, breather materials and bagging materials. The general procedure will be as follows: a. The tool is prepped with the appropriate mold release section 1. b. Apply the prepreg on the release tool. c. Apply one layer of peel ply or equivalent the same size as the part. d. A Bleeder is recommended if the resin content of the prepreg is over 42% or for very thick part over 0.5 thick. Two plies of 300gsm 7781 of E-Glass fabric or one ply of 610gsm woven roving can be used. e. Apply one layer on non-porous release film, Teflon or equivalent, over the lay-up; extending at least 1/2 inch past each edge of the part. f. Apply one layer of breather fabric over the lay-up ensuring that it forms a path to the vacuum port. g. Vacuum sources are preferable not be on the surface of the part. 1) There should be at least two (2) sources for any part larger than four (4) square ft. For larger parts, at least one vacuum connection should be provided for every 18 square ft. of laminate surface. 2) Where possible, the maximum distance to any point on the laminate surface should not exceed 60 inches. Protect against clogging with resin by applying extra breather under the vacuum port.
3) In case that the mold is not big enough to accommodate this type of arrangement you can place the vacuum port on top of the part by folding the bag and use 4-6 plies of breather. h. Apply the nylon bagging film and edge seal to tool with vacuum bag sealant. i. Evacuate the bag to at least 25 inches Hg and adjust the bag to eliminate wrinkles and bridging. j. Install a vacuum gauge at the vacuum probe connector. Allow the bagged assembly to stand for at least 15 minutes with an applied vacuum of at least 25 inches Hg. Remove the vacuum source and monitor the bag vacuum. Leakage may not exceed three (3) inches Hg in the first five (5) minutes after removing the vacuum source. Vacuum port Thermocouple 8 7 2 6 4 5 (Optional) 3 1 1. Tool surface 2. Tacky tape rubberized sealant tape 3. Prepreg laminate 4. Release film (peel ply porous teflon or equivalent) 5. Bleeder 6. 0.002 Airtech 234 TFP Non-porous teflon or equivalent 7. N-10 Airweave breather cloth 8. 0.002 Vacuum bag film
4.1 Recommended Shop Supplies Item Part No. or Specification Supplier Acetone 2-propanone (Acetone) purity 99.5% Sun Chemical, Dow, Ashland, Union Carbide Denatured Alcohol Ethanol - min 190% proof Ashland, Sofecia, Union Carbide, Eastman Chemical Release Film WL4600 (non-porous) WL5200 (non-porous) A4000R (non-porous) A5000 (non-porous) 200 TFNP-Brown Teflon 234 TFNP-Brown Teflon Richmond Richmond Release Agent Frekote 700 RAM 225 Breather A-3000 Airweave N10 Bleeder 7781 woven fiberglass cloth Peel Ply 200TFP (porous) - Teflon 234TFP (porous) - Teflon Release Ply B Nylon Sealant Tape GS 100 SM5126 Silicon Rubber Silicon Rubber minimum 375 F use temperature Bagging Sheet Film HS6262 WL7400 WL8400 Frekote Lilly Richmond Products JPS Industries Inc., BGF Industries Inc., Hexcel-Schwebel Richmond Circuit Supply Scnee-Morehead, Inc., Richmond Aircraft Products, Inc. De-Comp Composites, Inc Richmond Products
5 Cure Cycle All prepreg materials are to be cured according to tightly controlled time, temperature and vacuum requirements as shown in Table I. Quality Assurance shall continuously record time, temperature and vacuum during the cure process. Thermocouple wires should be used to monitor and record the temperature of representative test panels. One method is to place the thermocouple junctions at the laminate mid-plane and near the edge of the laminate where they will be trimmed off after the panels have been cured. Thermocouples may be placed outside the bag only if it has been previously demonstrated that there is negligible temperature difference between the inside and outside of the bag. The lagging thermocouple will be used to control the curing cycle in all the steps. Table I Cure Cycles a. Apply full vacuum, 27±2 in Hg b. Heat at 0.5 to 3 F/min to 160±5 F c. Hold at 160±5 F for 13±0.5hrs d. Cool at 5 to 7 F/min to 120 F or below before venting vacuum e. Remove from oven when oven temperature is 120 F or lower You can use alternative curing temperatures based on the table below. Temperature Curing Time Tg F, by DSC 160-165 F 13 hours 194 170-175 F 7 hours 203 180-185 F 5 hours 212 190-195 F 3.5 hours 221 200-205 F 2.5 hours 225 210-215 F 2 hours 230 220-225 F 1.5 hours 235 230-235 F 1 hours 240 240-245 F 0.5 hour 257 If the application requires maximum thermal resistance the laminate can be post cure at 250 F (125 C) for 1hr. The post curing can be done unsupported as long as the weight, the size and the shape of the panel will not introduce a distortion otherwise a minimal support is required. PACM s technical support group can recommend deviations, due to thick parts or high surface quality.
6 Bag Removal and Part Identification Before removal of the vacuum bag from the cured part, examine the bag for evidence of ballooning, charring, rupture, resin contact, tearing or other condition that would indicate bag failure during the cure cycle. Record any observation of unusual conditions on the shop traveler. Remove the vacuum bag. When removing the cured laminate from the tool surface, avoid the use of any sharp objects or tools that could damage the surface of the part or the mold. Avoid bending the cured laminate or the detail part. Do not remove any peel ply at this time. Each part or assembly shall be identified with the respective part number, shop traveler number and cure cycle number. If multiple parts are made on a single traveler (or Shop Order, Work Order, etc.) then each individual part shall be assigned a discrete serial number.