Lesson 8.3: Material Testing and Standards

🎯 Learning Objectives

• Understand why and how different material tests are performed on 3D printed parts.

• Interpret testing data to evaluate material performance.

• Recognize applicable international standards for additive manufacturing (AM) materials.

🔍 1. Mechanical Testing of 3D Printed Parts

Mechanical properties can vary significantly with printing orientation, infill, and layer bonding. Therefore, standardized testing is critical for validation and qualification.

📌 Tensile Testing

Standards: ISO 527 / ASTM D638

• Measures:

  • Ultimate Tensile Strength (UTS)

  • Young’s Modulus (Elastic Modulus)

  • Elongation at Break

• Test setup: Dog-bone specimens pulled until failure.

• Application: Predicts how much force a part can withstand in tension—key for structural elements.

📌 Flexural Testing

Standards: ISO 178 / ASTM D790

• Measures:

  • Flexural Strength

  • Flexural Modulus

• Test setup: Three-point or four-point bending.

• Application: Evaluates resistance to bending—important in brackets, beams, or clips.

📌 Impact Testing

Types: Charpy and Izod tests

• Measures:

  • Impact strength (energy absorbed before fracture)

• Application: Crucial for safety-critical parts (e.g., drone propellers, protective gear, automotive interiors).

• Orientation dependency: Layer lines significantly affect toughness.

📌 Hardness Testing

Types:

• Shore A/D (elastomers, soft plastics)

• Rockwell (rigid plastics, composites)

• Vickers or Brinell (metals)

• Measures: Resistance to localized plastic deformation.

• Application: Important for wear resistance and surface finish (gears, joints).

🌡️ 2. Thermal and Chemical Testing

These tests ensure thermal performance and chemical compatibility in harsh environments.

🔥 DSC – Differential Scanning Calorimetry

• Measures:

  • Glass Transition Temperature (Tg)

  • Melting Point (Tm)

  • Crystallinity (for semi-crystalline polymers like Nylon, PEEK)

• Application: Determines heat resistance, print temperatures, and post-processing stability.

🔥 TGA – Thermogravimetric Analysis

• Measures:

  • Weight loss vs. temperature

  • Thermal degradation

• Application: Used for thermal decomposition studies, flame retardance, and filler content analysis.

🧪 Chemical Resistance Testing

• Procedure: Expose printed samples to acids, bases, alcohols, or industrial solvents.

• Metrics: Mass change, dimensional stability, mechanical property retention.

• Application: Essential for labware, automotive, or food-contact applications.

📏 3. Dimensional Accuracy & Surface Quality

Print accuracy depends on printer calibration, material shrinkage, and post-processing.

🧮 CMM – Coordinate Measuring Machine

• Measures 3D coordinates of critical features.

• Used for tight tolerance parts (e.g., aerospace jigs).

🧭 3D Laser Scanning

• Non-contact method to compare part geometry against CAD files.

• Useful for reverse engineering or deformation analysis.

🔬 Surface Profilometry

• Quantifies surface roughness (Ra, Rz).

• Optical or stylus-based.

• Application:

  • In fluid dynamics, roughness affects flow.

  • In biomedical, it influences cell adhesion.

  • In mechanical parts, it affects friction and wear.

📚 4. Standards in Additive Manufacturing