Composites Repair

Question 1

List two broad categories for composite repairs.

Answer 1

• Mechanically fastened (bolted)

* Bonded

Question 2

List the strength and limitations for each repair category.

Answer 2

mech. - thick laminates require special fasteners

bonded- hot and cold

Question 3

List basic steps in the composite repair process

Answer 3

1. determine extent of damage
2. determine the materials and configuration
3. remove damaged plies and core
4. remove moisture (vacuum and heat)
5. Replace damaged core
6. replace plies
7. inspect
8. refinish
9. inspect
10. Document repair

Question 4

Describe the different types of repair materials

Answer 4

Wet layup, pre-preg

Question 5

List the four various NDT methods that can be used to inspect composite articles1

Answer 5

1. Pulse echo
2. tap test
3. thermography
4. through transmission

Question 6

Define scratch

Answer 6

damage to the finish

Question 7

Define crack

Answer 7

Damage to the matrix (1 piece, 2 pieces = break)

Question 8

Define dispond

Answer 8

Adhesive failure between the core and sheet

Question 9

Define delamination

Answer 9

Separation of plies

Question 10

The paint/finish removal methods

Answer 10

Hand sanding and blasting

Question 11

List ply removal sanding methods

Answer 11

Tapered and stepped

Question 12

Describe composite drying techniques

Answer 12

Heat and vacuum

Question 13

Instruction sources/materials and configuration

Answer 13

SRM, blueprints(original build data), repair manual, engineered data(approved by FAA)

Question 14

Describe the importance of repair material orientation of plies

Answer 14

The repair has to have the same strength as the composite, so the orientation of each layer needs to be the same on the repair as on the composite and use like material. Extra repair ply also must match.

Question 15

Class A repair

Answer 15

permanent repair

Question 16

Class B repair

Answer 16

Requires repetitive inspection

Question 17

Class C repair

Answer 17

Temporary Repair

Question 18

What technique do we use to remove finish?

Answer 18

mechanical technique, sanding with media blaster(other than sand)

Question 19

what does the term medial blaster refer to?

Answer 19

sanding with granules made of starch, plastic, walnut shells, ect.

Question 20

Two most important aspects of replacing the core?

Answer 20

use like material, and match ribbon direction of original structure.

Question 21

After you repair and paint a flight control, what must be accomplished to the flight controls?

Answer 21

they must be balanced. after balanced you put on balance rig and weight the whole airplane

Question 22

Why are composites typically not bolted on for a mechanical repair?

Answer 22

they are too thin, they need a thick laminate for that kind of repair.

Question 23

Two classifications of bonded repair?

Answer 23

Hot and Cold