Definitions /Dictionary/Glossary - nptel

Nonwoven Roving: Reinforcement composed of continuous rovings loosely gathered together.
Normal Distribution: A two parameter (μ, σ) family of probability distributions for which the
probability that an observation will fall between ‘a’ and ‘b’ is given by the area under the curve
between ‘a’ and ‘b’.
2
1 ⎡ (x − μ)
⎤
f(x) = exp⎢−
2 ⎥
σ 2π ⎢⎣ 2σ
⎥⎦
Normalization: A mathematical procedure for adjusting raw test values for fiber-dominated
properties to a single (specified) fiber volume content.
Normalized Stress: Stress value adjusted to specified fiber volume content by multiplying the
measured stress value by the ratio of specimen fiber volume to the specified fiber volume. This
ratio may be obtained directly by experimentally measuring fiber volume, or indirectly by
calculation using specimen thickness and fiber aerial weight.
NOT: Non-destructive testing. It is broadly considered synonymous with NOI.
Notch Sensitivity: The extent to which the sensitivity of a material to fracture is increased by the
presence of a surface non-homogeneity such as a notch, a sudden change in section, a crack or a
scratch. Low notch sensitivity is usually associated with ductile materials and high notch
sensitivity with brittle materials.
NPG Gel Coat: Neopentyl glycol gel coat has enhanced weatherability compared to non-NPG
gel coat.
Nylon: The generic name for all synthetic polyamides.
Nylon Plastic: Plastics based on a resin composed principally of a long chain synthetic
polymeric amide that has recurring amide groups as an integral part of the main polymer chain.
Observed Significance Level (OSL): The probability of observing a more extreme
value of the test-statistic when the null hypothesis is true.
Off-axis Laminate: A laminate whose principal axis is oriented at an angle (8) other than 00 or
900 with respect to a reference direction, usually related to principal load or stress direction.
Offset Shear Strength: (from valid execution of a material property shear response test) the
value of shear stress at the intersection between a line parallel to the shear chord modulus of
elasticity and the shear stress/strain curve, where the line has been offset along the shear strain
axis from the origin by a specified strain offset value.
Oligomer: A polymer consisting of only a few monomer units such as a dimer, trimer, etc., or
their mixtures.