PRINCIPLES OF COMPOSITE MATERIAL
MECHANICS 4TH EDITION GIBSON
SOLUTIONS MANUAL ACTUAL EXAM
PAPER 2026 QUESTIONS WITH ANSWERS
GRADED A+
⩥ how is work hardening possible in solids as compared to liquids.
Answer: solids have long relaxation times, liquids/glasses don't
⩥ what is the ideal plastic stress level. Answer: the stress level that leads
to flow in a polycrystalline material
⩥ strength vs dislocation density graph. Answer: a u-shape curve.
perfect crystal has high strength, but loses strength when there are
dislocations that can be propogated under lower stress, then as more are
added they start to interact and block each other.
⩥ taylor's theory of stress-strain relation in polycrystalline FCC metals.
Answer: under applied stress, dislocations move, interact with, and trap
each other. continued motion requires overcoming internal stresses of
dislocations, hence need increased applied stress for deformation.
⩥ strain vs dislocation density equation (orowans equation). Answer: γ =
ρ*b*l
,ρ = dislocation density at strain
b = burgers vector
l = average distance traversed by a disl
⩥ average separation distance between uniformly spaced edge
dislocations L =. Answer: 1/√ρ
ρ= dislocation density at strain
⩥ for a dislocation trapped due to interaction with dislocations spaced
distance L, the force F on the dislocation is =. Answer: τ*b = αGb²/R
⩥ for a dislocation trapped due to interaction with dislocations spaced
distance L, the shear stress τ on the dislocation is =. Answer: αGb/R
⩥ for a dislocation to move by bowing, R =. Answer: L/2
⩥ for a dislocation to move by bowing, shear stress τ =. Answer:
2αGb*√ρ
ρ = dislocation density at strain
b = burgers vector
, ⩥ the relationship between stress and strain in taylor's work hardening
theory is. Answer: parabolic
τ ∼ γ^(1/2)
⩥ taylor's work hardening theory limitations. Answer: assumes
uniformly spaced edge dislocations
screw dislocations are ignored (which can cross slip)
predicts parabolic stress-strain relation for polycrystals
⩥ what does annealing do. Answer: remove dislocations
⩥ work hardening effect on stress strain curve. Answer: increases the
amount of stress but decreases the amount of strain (shifts curve up-left)
⩥ grain boundary strengthening. Answer: interactions with grain
boundaries (done in BCC metals and alloys, various alloy steels)
⩥ solid solution strengthening. Answer: interactions with point defects
(done in carbon steels and other BCC alloys)
⩥ precipitation strengthening. Answer: interactions with precipitates
(done in Al alloys, nickel-based superalloys, PH steels)
MECHANICS 4TH EDITION GIBSON
SOLUTIONS MANUAL ACTUAL EXAM
PAPER 2026 QUESTIONS WITH ANSWERS
GRADED A+
⩥ how is work hardening possible in solids as compared to liquids.
Answer: solids have long relaxation times, liquids/glasses don't
⩥ what is the ideal plastic stress level. Answer: the stress level that leads
to flow in a polycrystalline material
⩥ strength vs dislocation density graph. Answer: a u-shape curve.
perfect crystal has high strength, but loses strength when there are
dislocations that can be propogated under lower stress, then as more are
added they start to interact and block each other.
⩥ taylor's theory of stress-strain relation in polycrystalline FCC metals.
Answer: under applied stress, dislocations move, interact with, and trap
each other. continued motion requires overcoming internal stresses of
dislocations, hence need increased applied stress for deformation.
⩥ strain vs dislocation density equation (orowans equation). Answer: γ =
ρ*b*l
,ρ = dislocation density at strain
b = burgers vector
l = average distance traversed by a disl
⩥ average separation distance between uniformly spaced edge
dislocations L =. Answer: 1/√ρ
ρ= dislocation density at strain
⩥ for a dislocation trapped due to interaction with dislocations spaced
distance L, the force F on the dislocation is =. Answer: τ*b = αGb²/R
⩥ for a dislocation trapped due to interaction with dislocations spaced
distance L, the shear stress τ on the dislocation is =. Answer: αGb/R
⩥ for a dislocation to move by bowing, R =. Answer: L/2
⩥ for a dislocation to move by bowing, shear stress τ =. Answer:
2αGb*√ρ
ρ = dislocation density at strain
b = burgers vector
, ⩥ the relationship between stress and strain in taylor's work hardening
theory is. Answer: parabolic
τ ∼ γ^(1/2)
⩥ taylor's work hardening theory limitations. Answer: assumes
uniformly spaced edge dislocations
screw dislocations are ignored (which can cross slip)
predicts parabolic stress-strain relation for polycrystals
⩥ what does annealing do. Answer: remove dislocations
⩥ work hardening effect on stress strain curve. Answer: increases the
amount of stress but decreases the amount of strain (shifts curve up-left)
⩥ grain boundary strengthening. Answer: interactions with grain
boundaries (done in BCC metals and alloys, various alloy steels)
⩥ solid solution strengthening. Answer: interactions with point defects
(done in carbon steels and other BCC alloys)
⩥ precipitation strengthening. Answer: interactions with precipitates
(done in Al alloys, nickel-based superalloys, PH steels)
