Volume 5 CDC

What do composite rely on to produce the required strength characteristics?

a combination of matrix type, fiber type, ply orientation, and processing method

What happens to fiberglass and graphite after the individual fibers are made?

they are bundled into groups called strands for fiberglass and tows of graphite

What effects does the finish of a composite fabric have?

it affects bond strength and durability, depending upon the resin type to be used

Why is aramid often used for ballistic protection and body armor?

aramid fibers have very good energy absorption characteristics

What properties make boron very popular for making repairs to metallic structures?

high tensile and compressive strength plus its lack of galvanic corrosion potential

What color are fiberglass fibers normally?

they are normally clear but appear white, and any color may be added during manufacture

What is laminated fiberglass construction?

two or more layers of fiberglass cloth saturated with a catalyzed resin and bonded together under heat and pressure

What is the core used for in a fiberglass honeycomb sandwich component?

to separate the outer facings and give the assembly a high degree of stiffness

How are graphite materials characterized?

by their high to ultra-high stiffness, high tensile strength, and low density

What is the most desirable property of graphite for high- performance structures?

the high stiffness-to-weight ratio

What is a woven fabric?

a material that is constructed by interlacing yarns, fibers, or filaments to form a fabric with specific structural and workability

How are woven fabrics produced?

by interlacing of warp (0 degrees) fibers and weft (90 degrees) fibers in a regular pattern or weave style

What is a UD fabric?

a fabric in which the majority of the fibers run in one direction only

What do true UD fabrics offer?

the ability to place strength in the component exactly where it is required and in the optimum quantity desired

What is the most common geometry available for honeycomb core?

hexagonal

What is a matrix?

a uniform resin material in which layered fibers of high-strength material are imbedded to create a composite structure

List five functions of the matrix in composite construction?

stabilizes the slender filaments against compression instability, carries transverse and laminar loads in the individual layers, provides the body to the composite in its cured state, prevents the filaments from drooping, and protects the filaments from abrasion and erosion

What are laminating resins and paste adhesives?

viscous materials that undergo a chemical reaction to generate a rigid structure

What is the purpose of a woven or nonwoven carrier material embedded in a film adhesive?

to prevent tearing during handling and to aid in bond line thickness control

What temperature do film adhesives require to cure?

a high temperature cure cycle, often 250 degrees or higher

How are foam adhesives most often used?

as lightweight splice material for splicing honeycomb core repair sections

List the four forms in which pre-preg materials are ready-to-use.

sheet, roll, tape, and mat

List three advantages of pre-preg materials over wet layup.

exact resin mix ratio, exact resin-to-fiber content ratio, and ease of handling/cutting the material

When developing a repair, how can you ensure that you get the correct layout shape?

by using a template

Describe how to use clear template material.

place it over the repair area, trace the required shapes, and mark the cutting lines with an appropriate marking pen

What is the purpose of a protractor?

to measure or create an angle

Why might you have to safe guard the templates that you make?

they may contain angles that coincide with classified aircraft angles

Why is a steel rule good to use as a straight edge?

it cannot be cut by the blades used to cut LO tape or boot layers

What is a key consideration during the design of stealth aircraft?

keeping energy concentrated in well-defined spatial aspects

How is planform alignment defined?

aligning all vehicle details with the OML angles of the aircraft

Why do LO platforms use planform alignment?

to prevent radar energy bouncing back to a receiver

What determines planform alignment angles?

the design of an aircraft

What are four shapes that are commonly used to match aircraft angles?

parallelogram, trapezoid, single- fastener diamond, and saw tooth

Explain opposite-wing alignment.

refers to using the leading edge angle of the nearest wing and the opposite wings as reference for alignment

Explain edge of part alignment.

refers to using the edge of the part that you are repairing as a guide for alignment

Describe how to perform a planform alignment using the edge of part method.

measures equal distances from the panel edges to the edge of the damaged coating, ensuring all sides are straight and all angles mirror the components

Where is the RAS where radar energy will typically be concentrated around an aircraft?

around the perimeter of the aircraft

What three components make up an RAS?

radar- transparent skin, loaded core, and reflector assembly

What is the conductive layer applied to the surface of an aircraft used for?

to dissipate the current over the whole surface of the aircraft

What must happen to the underlying nonconductive materials for the conductive layer to work properly?

they must be correctly mixed, applied, and tied into adjacent area to maintain continuity across the aircrafts surface

What is used as a barrier between LO coatings and metal structure?

a corrosion- inhibiting primer

What does a composite structure need to prevent underlying metallic assemblies from reflecting radar energy?

an electrically conductive coating

What are ceramics used for on aircraft?

as heat shields for fire protection and to provide thermal insulation

What are three advantages of using ceramics on aircraft?

they heat resistive, lightweight, and do not corrode

Why is ITO applied to transparencies?

it completes the conductive link from OML across transparency, while maintaining the highest levels of optical quality

What is applied to the surface of the aircraft to reduce the overall thermal signature?

IR materials

What is RAM used for in stealth technologies?

to disguise a structure from radar detection

What is dielectric RAM performance based upon?

the thickness, electrical loading, and type of dielectric material

In what forms is dielectric RAM available?

sheets, liquid, foams, and pastes

What is MAGRAM?

magnetic RAM and is a special coating that uses iron fillers set in a binder material

Where on an aircraft are resistive sheets typically placed?

the leading and trailing edges of the perimeter of the aircraft

What does resistive sheet do?

it transitions EM energy from a resistive body to a conductive body

AS an LO maintainer, what will you be required to use sealants for?

to bond sheet RAM and tapes, install fasteners, seal nut plates, and use as a weather strip

What will be the result of a “hot” sealant mixture?

a premature bond failure

What is the purpose of fairing materials?

to provide a smooth transition between two surfaces that have a mismatched height, also known as a step condition

In an RAS, what gives compressive strength to the aircraft skin?

the core

High strength and stiffness in composite- bonded materials is a result of the

concept of the cross-plied lamination

What is the identifying color for aramid materials?

yellow

What is a characteristic of graphite materials?

ultra- high stiffness

Unidirectional fabrics have the highest possible structural properties in fabric composite construction as a result of having

straight and uncrimped fibers

What essential function does resin matrix not perform?

carry the primary load of high-strength material

The process where viscous materials undergo a chemical reaction to generate a rigid structure is referred to as

curing

What type of adhesive is most often used as a lightweight splice material for a honeycomb core section splice repairs?

foam

When storing advanced composite materials in cold storage, what is the maximum temperature permitted?

0 degrees F

Cutting large batches of material into smaller sections the first time it is thawed is a process known as

kitting

Adding too much catalyst to your matrix produces what is known as a

hot mixture

When mixing a liquid matrix, the components should be

blended together slowly

What must you do prior to using the triple-beam scale?

zero the scale

The recommended vacuum pressure, measured in inches of mercury (inHg), for curing a repair is

15 inHg - 28inHg

Liquid moisture present in honeycomb sandwich assemblies is usually detectable by

x-ray

In a field environment, mitigate the effects of any moisture not removed during the drying process by using cure temperatures of or below

210 degrees F

What kind of ply lay-up would a laminate with a ply orientation of 45, 53,-45, -45, 53, 45 degrees be considered?

angle

What type of orientation would you choose to obtain approximately equal strength in virtually all directions when developing a ply lay-up?

quasi- isotropic

What can you do to help ease the reading of the ply orientation in a graphite repair site?

wet sand with 400 grit sandpaper

The first element of patch preparation is generating a

patch drawing

You would use a drill bushing and guide when drilling advanced composite laminates to ensure holes are drilled perpendicular to the surface and prevent

wobble

To compensate for the stresses of flexing in flight, the minimum required panel gap is

0.010

Which work procedure do you normally perform first when making a minor repair to a laminated fiberglass panel?

clean the damaged area thoroughly with an approved solvent

When making a minor repair to a laminated fiberglass panel, what is normally the third work procedure you use?

mix the resin according to the applicable technical order

What is the first step in a scarf repair?

remove any paint or coating

When repairing a minor metal-bonded honeycomb assembly skin delamination, you can prevent core damage when drilling holes for the resin injection by using a

drill stop

How are the thermocouples positioned when repairing a metal-bonded honeycomb repair?

equally spaced around the repair

Low observable technology gives an aircraft the ability to defeat radar, thermal, acoustical

and visual detection

The main purpose of making an aircraft low observable is to increase the aircrafts

survivability

The acronym RADAR stands for

radio detection and ranging

What is radar cross section (RCS)?

the size of an object as measured by radar

Radar cross section (RCS) is typically measured in square

meters

Condensation trails, glints, and paint schemes are sources of which radar signature?

visual

What type of aircraft signature source is generated by energy backscatter?

radar cross section

What is the most important factor for radar cross section (RCS) reduction of an object?

shape

Which reduction strategy uses painting an aircraft to match its primary mission?

visual

When you locate damage during an inspection, you will record length, width, depth/height, classification, and

orientation

What low observable verification tier is a whole body near field measurement?

III.

During a repair layout, what tool would you use to create or measure an angle?

protractor

The best way to create a straight line when cutting radar absorbent material (RAM) is to use a

steel rule

Arranging all aircraft details so that they coincide with the outer mold line (OML) angles of the aircraft is called

planform alignment

What alignment shape is widely used because it allows for smaller repair areas?

saw-tooth

When developing a repair in good planform alignment, you would align your repair with the aircraft

butt line

What do the resistive properties of the loaded core of radar- absorbing structure (RAS) do to the electromagnetic (EM) energy entering it?

weakens it

Dissipating an energy current over the whole surface of the aircraft is the purpose of the

conductive layer