Tensile Testing Methodology

Tensile Test Platform v1 — Testing Methodology

Purpose and scope

The Tensile Test Platform v1 is designed to generate repeatable, comparative tensile-strength data for FDM-printed polymer materials using a controlled, documented procedure. The primary goal of this platform is relative comparison: evaluating how materials, brands, colors, or print parameters perform against one another when tested under the same conditions.

While the test coupon geometry is based on ASTM rigid plastic tensile specimen proportions, this platform does not claim full ASTM compliance. The custom loading mechanism, lever-based force application, and dimensional variability inherent to FDM printing mean that results should be interpreted as comparative rather than absolute or certified values.

Test coupon geometry and measured dimensions

Coupons follow an ASTM-inspired rigid plastic tensile specimen shape with a defined gauge section intended to localize failure.

• Gauge width: 6.0 mm
• Gauge thickness: 3.0 mm (nominal; measured per coupon)
• The gauge section is used as the reference area for all stress calculations.

Because printed parts can exhibit dimensional variance due to extrusion behavior, cooling, and material shrinkage, thickness should be treated as a measured parameter, not an assumed constant.

Number of runs and reporting structure

Each material is tested using:

• 5 individual runs per material
• One coupon per run, loaded to failure
• Results are recorded per run and later summarized for comparison

This approach allows trends to emerge while helping identify outliers caused by print defects, anisotropy, or grip issues.

Test principle

Tensile load is applied using an arm-and-pivot lever mechanism driven by a rotational input. Instead of directly pulling the coupon with a linear actuator, the platform converts applied torque into tensile force through controlled geometry.

In simplified terms:

1. Rotational input applies torque to a driven gear
2. The gear applies force to a pivoted arm
3. The arm translates this force into a tensile load at the coupon grips
4. Load increases steadily until the coupon fails in the gauge section

This mechanical approach emphasizes repeatability and simplicity while remaining accessible for rapid iteration and material testing.

Overview of force and stress calculation

Rather than measuring tensile force directly, the platform derives tensile stress indirectly from known geometry and measured input values.

At a high level, the calculation process is:

1. Applied torque at the drive input is recorded at the moment of failure
2. Torque is translated into an effective force based on gear and lever geometry
3. The resulting tensile force at the coupon is calculated
4. That force is divided by the coupon’s gauge cross-sectional area to obtain engineering tensile stress

Final results are reported in MPa, with PSI provided as a converted reference value where applicable.

The calculation pipeline is fixed and consistent across all tests, meaning that while the absolute value may carry some uncertainty, relative differences between materials remain highly meaningful.

What this platform is best used for

The Tensile Test Platform v1 is optimized for comparative analysis, not certification-grade material characterization.

It is best suited for:

• Comparing materials or brands under identical print and test conditions
• Evaluating process changes (print temperature, cooling, annealing, orientation)
• Identifying relative strength trends across colors or batches
• Building a growing internal dataset where consistency matters more than absolutes

Because all tests share the same geometry, machine, calculation method, and assumptions, results are most valuable when viewed in context with one another, rather than against external datasheets or manufacturer specifications.

Practical limitations and assumptions

As with any non-standardized test platform, results are influenced by:

• Friction and compliance in pivots and gear interfaces
• Alignment and grip consistency
• Print-to-print dimensional variation
• Non-uniform strain rates inherent to mechanical drive systems

These factors reinforce the intended use case: controlled comparison within a single testing ecosystem, not cross-lab or cross-standard equivalency.

Test procedure summary

1. Print coupon using the documented material and print profile
2. Measure gauge width and thickness
3. Mount the coupon in the grips and verify alignment
4. Apply load until failure
5. Record maximum applied torque at break
6. Calculate tensile stress using the fixed platform model
7. Repeat for 5 runs per material and summarize results