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Failure Analysis and fractography of composite material - Coggle Diagram
Failure Analysis and
fractography of composite material
causes of failure
Manufacturing defects
properties that do not meet requirement/excessive amounts of defects
In service anomalies
service condition (misuse/unusual service conditions)
Design failure
poor structural design/material selection
Fracture modes
interlaminar failure
failure in which layers have separated
intralaminar failure
Failure through the thickness in which only matrix or fiber/matrix interface have been broken
Translaminar failure
Failure through the thickness in which fibers have been broken
handling failed samples
safety
Wear PPE (gloves, disposable clothing and respirators
Failed part may contain splinters, loose fibers and dust
Disintegrated fibers might be small enough to penetrate the lungs or cause skin irritation
Post failure damage
Preserve the original fracture surface
It refers to damage to the fracture surface after the failure event
Mechanical or chemical in nature
Makes interpretation of fracture surfaces difficult
Procedures
Collate background information
Materials laminate design, manufacturing method, service history, repair history.
Visual Inspection
Inspect fracture surfaces
Non-destructive testing
Identify internal and hidden fractures
prevent the destruction of important information during dissection
Photography
record of failed components before dissection
labelled and scale included
procedures
Confirmation of construction
Materialography: method to verify the stacking sequence of the product
Circular (fiber perpendicular to cutting direction), lines (parallel)
confirmation of materials
FTIR
Identify chemical species -- matrix type
DSC
glass transition temperature & residual heat of reaction -- degree of cure
Matrix Digestion and ignition
Remove matrix material -- fiber volume content
dissection
fractures surfaces may need to be cleaned before or after dissection
brushing with light fiber/dry compressed air for dust
ultrasonic bath and drying with vacuum to remove any chemical residues.
Microscopy
Scanning electron microscopy
more powerful and useful when high magnification and greater depth of field is required
Tension failure: radial lines
Compression failure: microbuckling & chop mark
Fractography: examinations and interpretation of surface
provide important clues about the cause of failure, the location and the sequence of events that lead up to failure
Crack path sequencing
Delamination occur first in this case as the fracture morphology is continuous across the ply split
