Composites test 2

54問 • 2年前

問題一覧

Describe advanced composite structure, what are two types?

Two or more laminated face sheets bonded to each side of a lightweight core material. Type 1. Honeycomb (nomex/aramid) Type 2. Solid (foam, balsa wood)

Is sandwich composite structure stiffer and stronger than just solid laminate structure?

Yes

What are 3 types of core material?

Foam, wood, honeycomb

Which core material has the greatest strength to weight ratio?

Honey comb

Describe the core material “foam”

Solid sandwhich

Describe the core material “wood”

Solid sandwhich

Describe the core material “honey comb”

Highest strength to weight ratio

In which direction can honeycomb core be pulled apart?

L direction / ribbon direction / “w direction will not tear”

When performing a composite repair, why is the ribbon direction important?

To maintain the original structure strength of the honey comb

What is honeycomb core that is made from aramid fibre paper (crimped ribbons) called?

Nomex

What are the advantages to using a nomex honeycomb core?

Excellent resiliency, low density, corrosion resistant, high strength to weight, flame resistant

What term is used for honeycomb core design having six sides

Hexagon

What term used to describe the bonded portion of the honeycomb cell wall?

Node

What is the term used to describe the portion of the cell wall that is not bonded?

Free cell wall

List four ways the core can be cut

Utility knife, putty knife, band saw, CNC machine

Is resin mixed by weight or volume?

Either way

List parts of the wet layup process that are required for a successful bond

•cut, measure/ weigh amount of fibre glass •place fibre glass between plastic •use shape template and trace repair •mix resin

What is a caul plate?

Smooth metal plates, free of surface defects, same size as composite lay up. Transmits surface and area temperature, used for alignment.

What are the units used to measure vacuum pressure? How do we check vacuum pressure?

Inches of mercury

What are the two most common types of composite inspection methods

Tap testing, GVI (general visual inspection)

Describe delamination?

Separation of the fibre glass layers, may affect single or multiple layers

When tap testing, how do we know if the bond is acceptable?

Good bond = sharp sound Damaged bond = dull thud sound

What is the most common cause of damage to composite structure?

•Human factors/ maintenance personnel •ground handling •bird strike

Where can information regarding damage, limits and repair to composite structure be found?

AMM and SRM

What can be required in a repair that will seal and add protection?

Sacrificial ply, gel coat

How are composites electrically bonded?

If a 1” diameter piece of core is being replaced, how wide will the repair be if there are 3 plies with .5” overlays.

4” inches

How can the edges of existing laminates be sanded and prepared for the repair?

•scarfed “mandrel and disc” •stepped edge “chamfered”

List important guidelines for mixing resin

Read crystals review

What is the desired fibre to resin ratio?

60% fibre 40% resin

What does resin rich mean?

Too much resin applied to a part can make the part brittle and increase weight of the part

What does resin starved mean?

A lack of resin decreasing the strength and will weaken the part

What is “exotherm”?

Mixed resin in extended period

What is pot life?

Time before mix of activated resin begins to solidify (time from mix to time the resin is unusable)

Resin shelf life

12 months

Storing of resin

Airtight, 10 degree c

What impact does temperature have in regards to matrix system cure time?

Too hot = becomes runny Too cold = thick and difficult to use

What type of equipment can be used to satisfy control and monitor the heating and cooling during each phase of a composite repair cycle?

•oven •auto clave •hot bonder •thermocouple

What is a thermocouple ?

A sensor that measure temperature. Used to measure resin temp during vacuum sealing

What are the two best methods of applying pressure to composite components?

•Vacuum bagging •compression mold/autoclave

What is a Weave?

A form made by interlacing threads passing in one direction with others at right angles to them

What is a loom?

A device used to weave cloth and tapestry

Warp/weft

The weft is the term for the thread or yarn drawn through, inserted over and under, lengthwise warp yarns that are held in tension on a frame or loom create a fabric cloth

Warp?

A direction of fibres running the length of the fabric as it comes off the roll or bolt.

Warp direction & orientation

Determines the strength and stiffness of the composite build

Isotropic ?

Material with stiffness and strength that are the same when measured in any direction through that material

Anisotropic meaning

Material with different strength and stiffness in different directions. Depends on fibre direction

Quasi isotropic

Material having isotropic properties, stiffness and strength are equal in all directions within the plane of the part.

Fabrics are manufactured in different styles such as?

•Unidirectional= strength in one direction •Bi-directional fibres =run in 2 or more directions •MAT =chopped fibres

Is plain weave an example of uni directional or bidirectional fabric?

Bidirectional

Two types of weave patterns

Plain weave & 2/2 twill

What are damage classifications for composite materials

Quality control, procedure oriented, quality assurance •Visual inspection •mechanical inspection •non destructive evaluation

What are additional causes of damage to composite structure ?

Erosion, fire, overload, lighting strikes, chafing

What tools can be used to finish or cut composite material in the dirty room?

Palm sander, 90 degree diegrinder

Composites test 2

Zachary Halycz · 54問 · 2年前

Composites test 2