Definitions /Dictionary/Glossary - nptel

Rule-Of-Mixtures: When combined, the properties of the composite material is some
combination of the properties of the two constituent materials. The composite property equals the
amount of the fiber property multiplied by the volume percentage of fiber, plus the amount of
matrix property multiplied by the volume percentage of the matrix.
S-Basis (or S-Value): The mechanical property value which is usually the specified
minimum value of the appropriate government specification or SAE Aerospace Material
Specification for this material.
S-Glass: A family of magnesium-alumina-silicate glasses with a certified chemical composition
which conforms to an applicable material specification and which produces high mechanical
strength. (ASTM D578-90)
S-2 Glass Fiber: The Owens Corning trademarked brand of high tensile strength "S" glass
fibers.
Sags/Runs: Sag - slumping of the gel coat or resin film. Run - draining of the gel coat film or
laminating resin.
Sample: A small portion of a material or product intended to be representative of the whole.
Statistically, a sample is the collection of measurements taken from a specified population.
Sample Mean: It is the arithmetic average of the measurements in a sample. The sample mean is
an estimator of the population mean.
Sample Median: Order the observation from smallest to largest. Then the sample median is the
value of the middle observation if the sample size is odd; the average of the two central
observations if ‘n’ is even. If the population is symmetric about its mean, the sample median is
also an estimator of the population mean.
Sample Standard Deviation: The square root of the sample variance.
Sample Variance: The sum of the squared deviations from the sample mean, divided by n-1.
Sandwich Construction: A structural panel concept consisting in its simplest form of two
relatively thin, parallel sheets of structural material bonded to, and separated by, a relatively
thick, light-weight core. It is defined as “A composite composed of a lightweight core material
(usually honeycomb or foamed plastic) to which two relatively thin, dense, high-strength,
functional, or decorative skins (also called faces) are adhered”.
Sandwich Lay-Up: A lamination composed of two outside layers of reinforced material such as
glass mat and an inside layer or layers of honeycomb, glass cloth, or other light-weight core
material.
Saturation: An equilibrium condition in which the net rate of absorption under prescribed
conditions falls essentially to zero.