Test Control and Data Analysis
The test setup is user-friendly, featuring a flow-chart style interface that guides user through programming the entire test procedure. With a single keystroke, the system automatically executes the loading and unloading sequences. Upon completion, it marks key feature points as specified by ASTM D5528, records the corresponding crack lengths, and calculates the fracture toughness values for each point.
I. Test Replay
The system enables point-by-point review of test data, synchronized with recorded video that visually displays the corresponding crack position and length throughout the test.
II. Calculation Methods
The G_IC value can be calculated using three methods in accordance with ASTM D5528: the Modified Beam Theory (MBT), the Compliance Calibration (CC) method, and the Modified Compliance Calibration (MCC) method.
Test Report
Clamp Fixture
Instead of using a hinge (Figure a) or loading block (Figure b) attached to one end of the specimen, which involves tedious, time-consuming steps such as surface polishing, adhesive bonding, and curing, a quick edge clamping method has been developed. This method, shown in Figure c, simplifies specimen preparation by tightening screws, significantly reducing preparation time.
Tracking and Measuring
Powered by an AI-trained model, the fracture recognition algorithm accurately identifies crack features, locating even tiny cracks at the pixel level within a large field of view. This eliminates the need to move the cameras to track crack progression. In real-time, the system measures crack growth and records the crack length along with corresponding displacement and load data, enabling automatic post-test calculations.
The software includes guided setup instructions to help operators correctly position cameras and lighting. Test operators can monitor fracture progression on-screen and view real-time data for crack length, load, and displacement.
System Overview
The system consists of a 1kN tabletop Universal Testing Machine, two high-resolution cameras with adjustable lighting, a mounting rack, a specimen holding fixture, automated crack length tracking and recording software, test control and analysis software, and a desktop PC equipped with a high-performance graphics card.
With a single keystroke, the system automates the entire loading and unloading test procedure, tracking and measuring crack growth on both sides of the specimen while synchronously recording crack length, displacement, and load data. Post-test analyses include point-by-point review along the test curve, identification of key feature points, calculation of results, and report generation.
Test Method
The test is performed using a double cantilever beam (DCB) specimen, which is a rectangular unidirectional carbon fiber-reinforced laminated composite containing a non-adhesive film at the midplane to serve as a delamination initiator.
In accordance with ASTM D5528, a tensile load is applied at a speed of 1 to 5 mm/min, causing the specimen to open while the corresponding load and delamination length are recorded. Once the crack length reaches between 3-5 mm, the specimen is unloaded to zero load at a speed of 25 mm/min, then reloaded at 1 to 5 mm/min until the crack extends at least 30 mm beyond the pre-crack point. At the end of the test, the specimen is unloaded to zero at 25 mm/min.
Test Machine
LE2103 Tabletop Universal Test System
- Maximum Force:1kN
- Class 0.5 accuracy
- 1 – 2500Hz Closed-loop Control
- Force Measurement Range: 0.1% -100%FS
LVR013 Automated System ASTM D5528 Composite Fracture Toughness Test