Q: Can you elaborate on the finite element tool that calculates the lamina properties?
Why is finite element needed for that? How close is this method to the commonly
known rule of mixture equations, etc.?
A: This model represents a hexagonally packed unidirectional composite at the micro
level. This is much more accurate since it accounts for the geometry of the microstructure.
The rule of mixtures cannot account for this. Firehole also supplies this micromechanics
model as a free online tool:
http://www.fireholetech.com/products/helius-matsim.aspx
Q: Is the fiber volume in the lamina data parametric or is it just reference information?
A: For now the fiber volume in the lamina is reference information. It can be entered
by the user if they know the fiber volume fraction of the lamina they are creating.
This value is automatically stored if the user uses micromechanics to create a lamina.
A new failure criterion, "MCT", will be implemented into future versions of CompositePro
which will use this fiber volume data. Please see
http://www.fireholetech.com/products/helius-mct.aspx?ref=mct.
Q: I did not notice a toggle for strain and stress on the lamina window. Can you
toggle between the two?
A: No you cannot toggle between the two. The calculate strains button is there to
calculate ultimate strains from ultimate stresses. Stresses can be calculated using
Hooke's law assuming linear elasticity.
Q: Is CompositePro’s method of finding properties applicable to compression molding?
A: Yes. Compression molding, as I understand it, uses bulk molding compounds (BMCs).
These materials are high resin content random directional composites. So, in CompositePro
one would simply create a lamina property that has the resin content of the BMC
and then create a 0/90/45/-45/-45/45/90/0 laminate using that lamina. The resulting
laminate properties should reasonably approximate a BMC.
Q: Does CompositePro include data for all types of polyesters?
A: CompositePro comes with material properties for only a generic polyester. However
you, as the user, can enter into the database as many polyester properties as you
would like.
Q: Would you please define the Failure Index and the formula?
A: The failure index allows the engineer to observe how close to failure a material
is when subjected to a certain stress state. When the failure index is zero, the
material is under a zero stress state. When the failure index reaches (or exceeds)
a value of one, the material is predicted to fail. The failure index calculation
is dependent on the failure criterion that is chosen. See the Helius:CompositePro
Reference Guide for more information.
Q: For progressive fiber failure, what is the criteria for the first fiber failure,
is it statistical or?
A: Failure is predicted in each ply using the current strain or stress state and
the strengths of the material. Failure can be predicted differently depending on
the failure criterion that is chosen in CompositePro. See the Helius:CompositePro
Reference Guide for more information including a brief explanation of each the available
criteria. Some of the criteria separately predict failure in the matrix and fiber
(i.e. Hashin and Puck) while others do not distinguish between the constituents.
Coming in Helius:CompositePro 4.1, a new failure criteria will be added. This criterion,
MCT, is based off of Multi-Continuum Technology which evaluates the stress and strain
in the matrix and fiber to predict failure in the separate constituents. If you
are interested in reading more about MCT visit:
http://www.fireholetech.com/multicontinuum.aspx
Q: Progressive failure: Can you elaborate on the use of degradation factors? How
were the default values determined?
A: The degradation factors specify the fraction of the original stiffness each material
property reduces to when a failure occurs within a ply. So for example let's say
E11 = 200 GPa and we set the degradation for E11 at 0.5 -- when a ply fails E11
for that ply will reduce to 50% of the original stiffness -- E11 will now be equal
to 100 GPa.
The default values are mainly based off of past results and have been used in CompositePro
since the early versions.
Q: Are the laminate survey results not dependent on the location of the layers through
the thickness?
A: The results in Laminate Survey are not dependent on the location of the plies
because Laminate Survey will build a balanced and symmetric layup. For instance
if we use the default angles (0, 90, 45), Laminate Survey will build the following
layup: [0, -0, 90, -90, 45, -45, -45, 45, -90, 90, -0, 0] -- it then uses this layup
and varies the thicknesses for each step. With the absence of moment loads, initial
failure in a balanced, symmetric laminate is independent of ply locations.
Q: Can you plot the progressive failure as you could on earlier versions or do you
have to export to Excel?
A: As for now you will have to export the data to Excel. This function will be available
in future versions of CompositePro.