NEi Nastran

NEi Nastran Progressive Ply Failure Analysis (PPFA™)

Composite Analysis Tool for the Design Stage

Progressive Ply Failure Analysis is the perfect tool for composite part advanced design. With composites being used increasingly in general public applications in all forms of products from transportation to sports, designers seek greater understanding of the nature and mitigation of catastrophic failures.
In many practical cases, the residual strength of a laminated composite part after the first-ply-failure (FPF) is still high enough to prevent the rupture of a component, so that applying FPF criteria for the design may lead to a too much conservative sizing, which is not desirable in some high performance applications where the weight penalty is a serious factor.
Progressive Ply Failure Analysis allows engineers to examine structural behavior beyond first ply failure and understand post FPF events of the composite material in the non linear field. PPFA can be used to perform:

Risk mitigation studies
Comparison of design alternatives
What–if studies for design options
Conceptual understanding of events beyond FPF

Common Design Questions and PPFA. Engineers involved in composite design are typically faced with questions and issues like:

What happens after First Ply Failure?
How much of a separation is there between FPF and ultimate strength
How much time does it take to go from FPF to ultimate failure?
What design modifications are effective in altering structural properties subsequent to FPF?
Do certain types of local damage compromise the overall structure?
How do variations in temperature affect performance?
Where does damage occur and what is the effect on structural properties?

Benefits of NEi Nastran Progressive Ply Failure Analysis.

Progressive Ply Failure Analysis provides the main tools and benefits of ply failure analysis without requiring the user to employ special elements and time consuming analysis techniques. PPFA benefits are:

Simple, easy to set up and use.
No additional material data is required.
Accurate and robust with failure direction sensitive criteria not found in tools that don’t incorporate LAR0C2 and Puck.
Examination of damage propagation / progression and effects on structural performance.
Captures the highly nonlinear discontinuous type failure typical in composites.
Nonlinear transient analysis uses all the advanced modeling capabilities in NEi Nastran like Automated Impact Analysis (AIA) and Automated Contact Generation

Here are two examples of that show the capability of Progressive Ply Failure Analysis:

Cantilever Beam Example
Comparison with Test Data

Cantilever Beam Example.

The present case is the simulation of a cantilever beam subjected to an enforced displacement on the free side, that generates a bending load in the structure.

The image below shows the constaint force vs. load increment plot computed by a non-linear static analysis, including the Progressive Ply Failure Analysis. The simulation is performed until the complete disctruction of the beam.

Progressive Ply Failure Analysis damage curve

Comparison with test data.

We compared the results from Progressive Ply Failure Analysis of NEi Nastran with esperimental results from specimen with hole, subjected to a tensile load. The technical paper that reports the experimental data is the following one:

Ref 1.

Progressive Failure Analysis Methodology for Laminated Composite Structures

The images below show the geometry of the the plate with hole and the finite element mesh, with a detail of the hole area.

progressife ply failure analysis specimen

Plate Geometry

L = 8.0 in (203.2 mm)
W = 1.0 in (25.4 mm)
d = 0.25 in (6.35 mm)

Layup Sequence and Total Thickness:

Layup: [0 / (±45)₃ / 90₃]s

Total n. of plies = 20

Total thickness = 0.103in (2.61mm)

Material Name

Cured Ply Thickness

Elastic Moduli

Strength Data

t mm (in)

E11 GPa (msi)

E22 GPa (msi)

G12 GPa (msi)

[-]

Xt MPa (ksi)

Xc MPa (ksi)

Yt MPa (ksi)

Yc MPa (ksi)

Sc MPa (ksi)

T300/1034-C

0.131
(0.00515)

146.9 (21.3)

11.38 (1.65)

6.185 (8.97)

0.3

1731 (251)

1379 (200)

66.5 (9.65)

268.2 (38.9)

133.7 (19.4)

Results

Failure Model	First Ply Failure N	Last Ply Failure N
Experimental Test [Ref. 1]	--	15670
Hashin [Ref. 1]	6761	14290 (-8.8%)
Christensen [Ref. 1]	6761	14510 (-7.4%)
LaRC02 (NEi Nastran)	6700	14017 (10.5%)
Puck PCP (NEi Nastran)	6700	13589 (-13.3%)
Tsai-Wu (NEi Nastran)	6400	13166 (-16.0%)
Max. Stress (NEi Nastran)	6600	17000 (+8.5%)

The following plot shows the non-linear load-displacement curve of the analysis, using different criteria for the calculation of the progressive failure of the laminated plate.

progressive failure analysis force vs. displacement plot