A-& B-Basis Allowables (AB_ALLOWABLE)
Features
Accurate prediction of A-basis and B-basis strength values
is critical to reduce risk in structural design of aircraft structures made
from composite material. This GENOA module effectively reduces the number of
coupon testing by simulating the scatter in composite material properties and
fabrication parameters. There are three distinct capabilities (options)
available for users of this GENAO module:
·
Option 1 using user provided test data: Predict A and B
basis strength values using user provided test data. This capability complies
with standards and recommendations from MIL HDBK 17E: Military Handbook for
Polymer Matrix Composites and FAA CFR 14 Aeronautics and Space. This option
does not involve progressive failure analysis. It is purely based on user
supplied test data.
·
Option 2 using virtual simulation combined with limited test
data: Predicts A and B basis strength values by reproducing scatter from
limited tests (one coupon strength value from each cure cycle of each batch is
recommended as input). This capability produces the scatter from few tests
supplied by the user by applying uncertainties on fundamental primitive
variables of constituent fiber and matrix properties and composite fabrication
parameter. User can iterate on coefficient of variation of the random variables
to collectively reproduce the scatter in the test. This analysis option
combines progressive failure analysis (FEA based) or PFA Unit Cell with
probabilistic method to fit the scatter from the test. The PFA Unit Cell
allowables capability can be applied to any un-notched coupon producing
allowables strength values in few minutes. On the other hand, the PFA based
allowables can be applied to any ASTM type test or any structural component
level. A by-product of this analysis is the sensitivity information which
ranks the influence of the random variables on the material strength.
·
Option 3 virtual simulation without test data: Estimates
A and B basis strength values by virtual generation of scattered strength for
coupon or structural component. The code generates strength response by
perturbing material fiber/matrix/interface/ply properties and/or composite
fabrication variables using user provided coefficient of variation. The
analysis process relies on PFA to collect final strength data for perturbed
random variables (above and below the mean) to simulate coupon test behavior.
Once the various strength data are collected, the data are passed to option 1
again as if they were real test data to assess A and B basis values using Mil
HDBK procedures. This capability is very effective when no test data are
available and can be used as a guide to material selection.
Applications/Benefits:
·
Effective tool to reduce risk in structural design.
·
Reduces the number of coupon tests needed for material
qualification.
·
Accelerates material qualification for certification.
·
Provides a guideline to material selection when no test data are
available.
·
Evaluates scatter in material strength.
·
Applicable to all types of material architectures, all types of
ASTM tests, and all levels of structural components.
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