JEC COMPOSITES MAGAZINE - Issue #98 - July/August 2015 - 49

Fig. 8: Failed composite components from the vertical tail of the A300-605R. (Courtesy of NTSB/NASA) [2]

From inspection to prevention
The power of fractography lies in the fact that essential information for the understanding of composites performance can be
gleaned, otherwise impossible by simply analysing experimental
data or numerical models. In particular, using the aforementioned fractographic tools, apart from information on the
failure mechanisms and failure processes, the analyst can also
obtain information pertaining to processing and manufacturing
defects, chemical damage or damage induced by machining or
during assembly which may have deteriorated the performance
of the composite. In light of the complex failure mechanisms
and the inherent susceptibility of composites to defects, the
identification and documentation of the failure processes and
such anomalies is of great importance for the end-user since it
offers essential information that can lead to better performance
and failure prediction and, ultimately, facilitate failure prevention. Where composites are introduced in new and demanding
areas such as primary structures using novel processing and
manufacturing techniques and complex architectures (e.g.
stitched, NCF), end-users can greatly benefit from the feedback
that fractographic analysis can provide, ranging from improvements in processing and manufacturing to inhibiting in-service
failures.

A black art or an invaluable tool?
The field of composite materials fractography has been continuously developing for nearly forty years. Analysts can now relate
fracture morphologies to failure mechanisms with confidence
and provide information about the failure sequence and source
of failure initiation. However, when in its infancy, fractography
was considered as "black art". Even today, the notion that one
could identify the source and location of failure in a composite component by examining broken pieces in some cases not
larger than a few millimetres can still be inconceivable to some.
However, fractographic analysis is a very methodical and timeconsuming process conducted with scientific rigour. To conduct
a fractographic analysis and reach sound conclusions, the analyst is expected to be competent in a wide range of disciplines
such as fracture mechanics, materials science and microscopy,

amongst others, and have the capability to deduce complex
failure processes. Fractography of polymer composites is a
powerful technique capable of providing essential qualitative
information for processing and manufacturing, quality of the
constituents and their interface, failure mechanisms and processes as well as the source and location of failure. In addition,
fractography can gauge experimental observations to numerical
modelling predictions and verify the validity of predictive models. Therefore, considering the wealth of information one can
obtain from this post-mortem analysis, fractography is regarded
as an invaluable tool for the design and analysis of polymer
composites.

Case study
American Airlines Flight 587/A300-600R accident
In 2001, an American Airlines A300-600R crashed soon after
take-off from John F. Kennedy airport in New York City. This
accident was probably the first to involve the failure of a primary
composite aerostructure (Figures 7 & 8). In the aftermath of
the accident, the use of composite materials in flight-critical
applications received fierce criticism due to speculations about
the cause of the accident having been due to manufacturing
defects, fatigue damage or overloading of the composite tail fin.
However, the comprehensive fractographic analysis conducted
by NASA and NTSB reported that the cause of the accident
was due to a pilot error (overuse of the rudder) that ultimately
caused the detachment of the tail. n
More information:
spyros.tsampas@swerea.se
e.greenhalgh@imperial.ac.uk
References
[1] Composites Leadership Forum, Lightening the Load, 2014
[2] NASA/TMX-2003-000000, "Structural Analysis Report on
the American Airlines Flight 587 Accident - Part 2 - Global Fin/
Rudder Structural Analysis and Assessment"
[3] In-Flight Separation of Vertical Stabilizer American Airlines
Flight 587, Airbus Industrie A300-605R, N14053,
Aircraft Accident Report, NTSB/AAR-04/04

No98 July - August 2015 /

jec composites magazine 49
Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #98 - July/August 2015
