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Clarifying the Fracture Mechanism of Composite Materials Strength Evaluation Technique Helps Improve Accuracy of
– Observing the Fracture Process of CFRTP Materials – CAE Analysis for Composite Materials

– In-Plane and Out-of-Plane Shear Properties of Thermoplastic CFRP Materials –

Carbon fiber reinforced thermoplastic (CFRTP) materials offer excellent workability, mass producibility, and recyclability. Consequently, they are expected to In recent years, automotive manufacturers have been considering the use of carbon fiber reinforced thermoplastics (thermoplastic CFRP) for automotive
replace metals and other conventional materials in general purpose transportation equipment and especially in mass produced automobiles. However, due structural materials, where high strength and durability are required, due to the higher specific strength and superior workability and formability of
to an inadequate understanding of the internal fracture mechanisms that occur during the deformation process associated with the static strength, fatigue thermoplastics compared to conventional materials.
strength, and various other properties of CFRTPs, discussions about evaluating the safety of CFRTP have not progressed. Therefore, the following describes Unlike conventional homogeneous materials, anisotropic thermoplastic CFRP composite materials exhibit a complex fracture behavior due to tension,
a combination system able to observe internal damage in test specimens as loads are applied, which is useful for determining CFRTP fracture mechanisms. compression, bending, in-plane shear, out-of-plane shear, or a combination thereof, depending on the principle axis and direction of the stress applied.
Therefore, those performing evaluation testing for product design purposes by CAE, for example, have been highly demanded test methods that is able to
Description evaluate and validate reliably the respective types of fracture behavior.
Fatigue Testing Inside an X-Ray CT System In-Plane Shear Test—Using Virtual Strain Gauges (DIC Analysis) to Evaluate Localized Strain Dependence

Observing Progression of Fatigue Cracking
During Fatigue Test of Aluminum Test Single-point measurement (ASTM D7078)
Specimen Evaluates shear strain using a biaxial strain gauge
Some thermoplastic CFRP materials with high
This system is able to capture CT images of test Jig Jig
mechanical performance can generate localized strain.
specimens mounted in a fatigue testing machine Camera Strain behavior cannot be determined accurately
(air servo). using conventional strain measurement methods.
Note: Tests are paused during CT scanning.
Evaluation of in-plane strain distribution (DIC Analysis)
Bridge box Correlation Evaluation of Fracture Images to Stress-Stroke Graph
DIC data Max. principal strain Max. shear strain
analysis position
inspeXio SMX-225CT HR Plus Fatigue cracking (progressive cracking) (prior to fracture) Evaluates the maximum principal strain and
(initial onset) distribution of maximum shear strain to
determine strain measurement points.
Tensile and Compression Testing Inside an X-Ray CT System Multi-point measurement Virtual strain gauges (DIC Analysis)
Evaluates localized strain.
Deviation angle [deg]
Test Specimen Shape Areas to attach strain gauge and apply random mark Evaluation of Localized Strain
(Comparison of Strain Gauge and Virtual Strain Gauge)

· Strain gauge measurements (four channels) can be used for ASTM D7078 compliant in-plane shear test evaluations.
· DIC Analysis can be used to evaluate multi-point strain measurements based on in-plane strain distribution and virtual strain gauges.
(after applying tension) (before applying tension)
Felt Tensile Testing Results
Tensile Testing Machine The results show that many fibers are oriented in the zero-degree direction (direction of tensile force)
after applying tensile force. Out-of-Plane Shear Test—Development of a New Test Method Using CAE Analysis
Three-Point Bending Testing and Stress Measurement Inside an X-Ray CT System
Using CAE Analysis to Strain Gauge Measurement in Micro Areas
Optimize Test Specimen Shape Out-of-Plane Shear Test Observations of Test Specimens (X-ray and Microscope)
Non-Planar Image Non-Planar Image Non-Planar Image Non-Planar Image Non-Planar Image
Indenter

Test
specimen Shear properties at A-3 and A-4: Low
Damage
Load cell depth Creating FE Model of Test Specimen
Frame Strain Gauge Measurement Results
Specifying Test
Stroke: 0.0mm 5.22mm 6.63mm 7.23mm 8.53mm
Three-Point Bending System Specimen Shape
Large stroke Three-Point Bending Test and Observing Internal Structure of CFRTP
The damage inside a test specimen can also be observed as a graph of stroke and
A-1 A-2 A-3 A-4
stress is acquired. Shear fracture Shear and bending fracture
(Available) (Not Available)
This research was performed as part of the "Research and Development of Innovative New Structural Materials" project
commissioned by METI and NEDO. Test Specimen Observation (Fluoroscopy Image)
Dependence of Out-of-Plane Strain Distribution on Test Specimen Fixing Jig and Parallelism A-3 with the lowest shear properties and where only
Test Specimen Shape (CAE Analysis) Adjusting Platen shear fracture occurs is the optimal test specimen shape.
· The combination system was created by a manufacturer specializing on X-ray CT systems and testing machines!
· Changes in stresses experienced by test specimens and the process of internal damage progression can be observed, which · Nonlinear behavior of out-of-plane shear, which was previously difficult to measure, can be evaluated through new test method.
was previously difficult to do.
Acknowledgments
Some of this research was performed as part of the "Research and Development of Innovative Structural Materials" project commissioned by METI and NEDO, and we wish to express our gratitude to the parties involved.

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