JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015 - 54

simulation

Simulation and analysis of composites challenges and opportunities
Composites offer many advantages in terms of stiffness, weight reduction, corrosion resistance, and fatigue performance. These advantages have led to the increased use of these materials in a variety of
industries. To fully utilize composites in the most efficient and beneficial manner, design and analysis tools will need to continue to evolve
and improve. The industry is making tremendous progress but we
are still far away from being able to design composite structures with
the same confidence and efficiency as with isotropic materials such
as metals and plastics. As with any worthwhile undertaking, the process for addressing the challenge will yield improved understanding
and new design methods that will benefit the product development
community, leading to better and more sustainable products.

omposite materials have made their
mark in the aerospace industry due
to their light weight, high stiffnessto-weight ratio, excellent fatigue durability, and corrosion resistance. They have
also been prominent in sporting goods
and wind energy. They are now making
their way into other industries including
automotive, marine, energy, construction, and consumer products. These
materials offer tremendous advantages
but they also introduce many more
complexities in the design and analysis
of composite structures.

is also important but once one is selected, the designer only has to deal
with shape and/or thickness changes to
create a design that meets requirements.
Composite structures are non-isotropic
meaning their material properties have
directionality - i.e. they have different
properties in different directions. This is
most significant with continuous fibre
composites where the stiffness in the
fibre direction is generally an order of
magnitude greater than transverse to the
fibre direction. Even for chopped fibre

Design issues
The design and analysis of composite
structures is quite different than with
metal structures. Metals are isotropic,
meaning their material properties are
not direction dependent. The only
variables that a design engineer needs
to consider are generally shape and
thickness. The selection of the material

By
Robert Yancey
VP - Aerospace Solutions
Altair Engineering

composites, there is some directionality in the material properties unless the
fibre orientation is completely random,
which is rarely the case.
In addition to directionality issues,
laminate composites also have the additional variables of ply orientation and
stacking sequence to consider. Thickness
variations for laminate composites also
are more complex because these require
ply drop-offs or ply build-ups to affect
these thickness changes. The drop-off
or build-up zones
create regions that
can affect potential
failure modes in the
part and they have to
be engineered carefully to not create
weak areas that can
precipitate failure.

Fig. 1: Overview of 3-phase approach for composites optimization with
OptiStruct

54 jec composites magazine / No94 January - February 2015

The addition of so
many variables to
the design process

JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #94 - January/February 2015