Composite Structures Flashcards
The general definition of composites
Combinations of two or more materials that differ in composition and form
The description of composite strength to weight ratios
High strength to weight ratios for composites
The part of a composite which provides the majority of the structural strength
Reinforcing fibers
2 structures that can be used as the core for sandwich structures
- foam blocks 2. honey comb structures
The material that fiberglass cloth is constructed from
silica glass
The disadvantage of using fiber glass compared to using other types of composites
Fiberglass has a weaker strength-weight ratio compared to other composite types
The two most common types of fiber glass
S- glass E-glass (electric glass)
The 5 most common reinforcing fibers used
- Fiber glass 2. Aramid (Kevlar) 3. Carbon fiber 4. Ceramic 5. Boron fiber
The reinforcing fibber best suited for use in areas subject to high vibration
Aramid
The best typical advantage of Aramid in typical aviation
The ability of the this particular reinforcing fiber to flex and absorb stress (such as helicopter blades)
The major disadvantage of Aramid
The con of the this particular reinforcing fiber to stretch easily which makes it difficult to repair
The best typical advantage of Carbon Fiber in typical aviation
High compression/ bearing strength and stiffness
The major disadvantage of Carbon Fiber
The con of the this particular reinforcing fiber to be Cathodic
The type of reinforcing fiber which is critical to keep from coming in contact with aluminium
Carbon Fiber
The reinforcing fibber best suited for use in areas subject to high temperatures
Ceramic fibers
The reinforcing fibber that will retain most of it’s strength when subjected to intense temperatures
Ceramic fibers
The primary reason for arranging fibers in various orientations, in a fiber matrix system
To recover some of the lost strength in a composite due to the use of resin which makes the structure more brittle
The primary difference in strength between a sheet of metal and a sheet of composite
Metal tends to have the same level of strength in all directions while composites have strength only in the direction of the plies
The reason why wings made out of composites, will have plies running the length of the wing, 45 degrees and 90 degrees
A wing is subjected to torsional loads which will run along the wing length, wing chord and every angle inbeween
The 3 names of the orientations of threads of reinforcing fibers
- Weft/Fill 2. Warp 3. Bias
The description of a pre-impregnated fabrics
Fabrics of reinforcing fibers which already have resin contained between the fibers
Orientation of the reinforcing fiber threads in the direction it comes off of the roll
Warp definition
Orientation of the reinforcing fiber threads in the direction perpendicular to the warp fibers
Weft/ Fill deinition
Orientation of the reinforcing fiber threads diagonal to the warp fibers
Bias definition
The types of reinforcing fiber fabric styles
- Unidirectional 2. Multi-directional
The type of fabric style which is most resistant to “fiber breakout”, and delamination
Fabric weave benifits
The purpose of matrix system in a composite structure
The holding in place of the reinforcing fibers and transferring of external loads to the fibers
The term for the ability of the matrix to transfer external loads to the reinforcing fibers
Interface
The name of the organic polymer which is used as a matrix
Resin
5 types of resins
- Thermoplastic resins 2. Thermosetting resins 3. Polyester resins 4. Epoxy resins 5. Adhesives
The most common method of testing a composite structure for delaminations
Coin Tapping testing method
The process that can slow down the cure rate of a resin
Refrigeration
Prior to curing, pre-impregnated fabrics typically contain ____ % resin
50% resin
During the curing process of a pre-preg, some of the resin bleeds out producing a structure that contains ____% resin and ____% fibers
40%, 60%
The way that pre-pregs must be stored
Stored in a freezer to prevent curing
Another term for a thixotropic agent
Another term for a filler
Thixatropic agents are added to resins and perform 3 functions
- Control viscosity 2. Control weight 3. Increase pot life
3 common fillers/ thixotropic agents
- Microballoons 2. Chopped fibers 3. Flox
Micro balloons can be manufactured from these two materials
- Plastic 2. Glass
The material of thixotropic that is compatible with resin
Glass
The chief advantage of using micro balloons as a thixotropic agent
Provides greater concentrations of resin in the edges and corners of a structure
Chopped fibers and flox primary benefit and how it’s used
Adds strength to the structure and is mixed with resin
The type of matrices that are still in the developmental phase
Metal matrix
The means of composite fabrication in which prepreg fibers are directed through a placement device onto a mandrel
Filament winding method
When a member is bonded between two thin face sheets the structure is termed
Sand which structure
The greatest type of strength that a sandwich structure has
Compression strength
The brand name of a widely used honeycomb structure in aviation which is created from paper impregnated material
Nomex
The general definition of Interply hybrid laminated composite structures
two or more layers of different reinforcing material laminated together
The direction in which the honeycomb structure can be pulled apart is termed
Ribbon direction definition
The definition of shelf life for a resin matrix
The time that the product is still good in an unopened container
The term for when too much resin is applied to a matrix mixture or part
Resin rich
The term for a when not enough resin is used for a part
Resin lean
When working the resin into the fibers care should be taken to not distort the_____
fabric weave
Where the information about the health precautions, hazardous ingredients, flammability, ventilation requirements, spill procedures and transportation/ labeling requirements are found of a part
Material Safety Data Sheet (MSDS)
The most commonly used method to apply pressure to composite repair
Vacuum bagging
principle of why vacuum bagging works
When pressure is removed from the sealed bag, atmospheric pressure can act on it
The manufacturing technique of composite manufacturing which is the most flexible procedure and can be done anywhere
wet-lay
The term for the method of dissipating the electrical charge on composite structures
Bonding
3 types of electrical bonding on composites
- Aluminium wires woven into the top layer of composite fabric 2. Thin sheet of aluminium foil bonded to the outtler layer 3. Aluminum flame sprayed onto the component
Composite structure finishes protects the structure from these two things
- moisture 2. UV light
6 types of NDT testing that can be used on composite structures
- Back light test 2. Tap (coin) test 3. Ultrasonic 4. Radiography (X-ray) 5. Thermography 6. Dye penetrant
Description of Back light testing on composite structures
Shinning a strong light through the composite structure to look for cracks and delaminations and water
What a delamination on a composite structure will look like during a back-light test
a bubble or a change in color
The step that must be taken prior to inspecting a composite structure with the use of the back-light test method
The composite structure must be stripped of all paint prior to
The effectiveness of a coin tap test on a composite structure will decrease with
an increase in material thickness
The most commonly used NDT testing of composite structures
Ultrasonic inpection
Principle of operation of ultrasonic NDT on composite structure
Sound does not travel back to the receiver as fast through a delamination compared to no damage
The NDT that can detect water trapped inside a honeycomb structure in a composite structure
X-ray, backlight
How thermography is used to detect damage on a composite structure
Heat is applied to the composite and the damage will show up as temperature gradients using an infrared camera
The issue between using liquid dye penetrant and succeeding repairs on composite structures
Fibers absorbed by the dye will not bond to new material for a repair
In drilling of a composite structure, delamination and breakout is most likely to occur when
when the drill pushes out on the other side of the composite structure
To reduce the possibility of damage to a composite structure when drilling it, the drill bit must be
sharp
To prevent delamination and breakout damage of a composite when drilling through it, drilling should be done with
a wooden block behind the surface
In drilling a composite structure blindly, and the backside of the structure isn’t accessible for a wooden block, this precaution must be done
measure precisely the depth of the drill bit
The best material/ type of drill-bit to use in drilling through composites
carbide drills
Operation if a water-jet cutter
water is applied with a pressure of 50,000 psi through a pinhole nozzle
The literature to find all the material required for a repair on a composite material
Structural Repair Manual (SRM)
The only method which is used to remove the surface finish on a composite structure
Sanding
The instrument used to remove the damaged part of the composite structure, especially structures with honey-comb cores
Router
The 3 steps in Step Cutting damage out of a composite structure
- Outline the entire damaged area that must be cutout and removed 2. Expand the repair radius (if circular) by 1/2 an inch for every ply that must be repaired 3. Extend the radius by an additional one-inch if an overlap patch is called for
Which numer is the Ribbon Direction
2
The 4 basic types of composite repairs
- Bolted metal
- Bonded metal
- Resin injection
- Lamination of new plies
The main reason why bolted or bonded patches are not perfered means of composite material repair
Bolted and bonded patches do not restore structure to orignal strength
The most desired type of compiste structure repair
Lamination of new repair plies
The 4 major types of damage to composite materials
- Cosmetic
- Impact
- Cracks
- Holes
Description of the water-break test and when its useful
Prior to bonding, a means of cleaning the surface
Flushing the part with room temperature water and looking for water beads on the surface which indicate more cleaning is required
