Structures and materials

Question 1

Fail safe

Answer 1

structure is designed to include multiple load paths so failure of one component does not cause critical failure

Question 2

Damage tolerant

Answer 2

structure is designed to withstand a degree of damage due to impact,corrosion and fatigue and still remain adequate strength until problem is detected

Question 3

Load factor

Answer 3

Load factor = Lift/aircraft weight

Question 4

Limit load

Answer 4

maximum load expected in service, results in no permanent deformation of the structure

Question 5

Ultimate load

Answer 5

defined as limit load times a safety factor

Question 6

Fatigue

Answer 6

generally defined as weakening of the structure under cyclic load conditions

Question 7

Fatigue life

Answer 7

defined as the time taken to initiate a crack which would reduce the strength of a component

Question 8

Static strength

Answer 8

ensures a structure such as a wing can withstand extreme loads caused by e.g. wind shear or other large transient forces

Question 9

Fatigue strength

Answer 9

measures durability of a structure

repeated mechanical loading of a structure to determine failure points

Question 10

Stressed skin semi-monocoque

Answer 10

skin is load bearing
skin supported internally by structural components
internal structure reduced
no external bracing required

Question 11

Benefits of a stressed skin semi-monocoque

Answer 11

high strength to weight ratio
provides large unobstructed internal volume
easily formed into aerodynamic shapes
max internal volume for minimum surface area
lends itself to modern mass production

Question 12

Spar

Answer 12

carry vertical loads

provide a main load path to resist bending

Question 13

Ribs

Answer 13

resist torsional loading

minimise buckling

Question 14

Stringers

Answer 14

support and stiffen skin

contribute to bending resistance

Question 15

Skin

Answer 15

load bearing
transfer aerodynamic loads into spars
resist shear loading in torsion

Question 16

Wing box

Answer 16

uses spar, rib and skin stringer panels to form a box section
low mass
high strength
resist bending and torsional loads

Question 17

Basic fuselage loads

Answer 17

pressurisation- hoop stress
mass- inertia
empennage surfaces-bending and torsion
main plane-lift

Question 18

Longerons

Answer 18

longitudinal strength

resist fuselage bending

Question 19

Frames

Answer 19

carry hoop stress

reduce buckling length

Question 20

Bulkheads

Answer 20

reinforce areas of high stress concentrations

Question 21

Benefits of composites

Answer 21

low mass
high tensile strength
stiffness
low thermal expansion
formability
corrosion resistance
reduced parts count