Impact Testing of Materials
Significance and Purpose
Impact Testing evaluates a material’s ability to withstand sudden forces or shocks, assessing toughness, fracture behavior, and energy absorption. It is crucial for automotive, aerospace, construction, packaging, and consumer goods industries where materials experience dynamic loading conditions.
This type of testing provides insight into:
- Material Toughness: Ability to resist crack propagation under sudden impact.
- Fracture Mechanics: Distinguishing between brittle and ductile failures.
- Energy Absorption: Measuring how much energy a material can dissipate before failure.
- Failure Modes: Identifying material behavior under rapid deformation conditions.
This summary covers pendulum impact tests (Izod and Charpy), instrumented and uninstrumented impact tests (Dynatup, Falling Dart), and multiaxial impact testing, as defined by ASTM and ISO standards.
Relevant ASTM and ISO Standards
Pendulum Impact Tests
- Izod Impact Testing (single-edge notched specimens):
- ASTM D256: Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics.
- ISO 180: Plastics — Determination of Izod Impact Strength.
- ASTM D4812: Standard Test Method for Unnotched Izod Impact Strength of Plastics.
- Charpy Impact Testing (center-notched specimens):
- ASTM D6110: Standard Test Method for Determining the Charpy Impact Resistance of Notched Specimens of Plastics.
- ISO 179: Plastics — Determination of Charpy Impact Properties.
Instrumented and Uninstrumented Drop Impact Tests
- Dynatup Instrumented Impact Testing (measures load, energy, and deflection):
- ASTM D3763: Standard Test Method for High-Speed Puncture Properties of Plastics Using Load and Displacement Sensors.
- ISO 6603-2: Multiaxial Instrumented Impact Testing for Plastics and Composites.
- Falling Dart Uninstrumented Impact Testing (determines failure energy without sensors):
- ASTM D3763
- ISO 6603-1: Multiaxial Impact Testing for Plastics Without Instrumentation.
Low-Speed Multiaxial Punch Testing
- ASTM D3763: Standard Test Method for High-Speed Puncture Properties of Plastics Using Load and Displacement Sensors.
- ISO 6603-2: Multiaxial Instrumented Impact Testing for Plastics and Composites.
These standards ensure consistency and repeatability in impact resistance testing for various materials.
DatapointLabs Tests for Impact Testing
Tests in the DatapointLabs test catalog that reference impact testing are as follows:
General Impact Testing (inquire regarding material suitability)
| Test ID | Test Description | Standards |
|---|---|---|
| M-425 | Izod Pendulum Impact | ASTM D256, ISO 180, ASTM D4812 |
| M-427 | Charpy Pendulum Impact | ASTM D6110, ISO 179 |
| M-410 | Dynatup Instrumented Impact | ASTM D3763, ISO 6603-2 |
| M-412 | Falling Dart Uninstrumented Impact | ASTM D3763, ISO 6603-1 |
| M-411 | Low Speed Multiaxial Punch | ASTM D3763, ISO 6603-2 |
Principle of Operation
- Pendulum Impact Tests (Izod & Charpy):
- A pendulum hammer is released from a set height to strike a notched or unnotched specimen.
- The energy absorbed before fracture is measured.
- Instrumented Dynatup Impact Test:
- A high-speed striker impacts the specimen, and load sensors capture force, energy, and deflection in real-time.
- Falling Dart Uninstrumented Impact Test:
- A weighted dart is dropped onto the specimen to determine the impact energy required for failure.
- Low-Speed Multiaxial Punch Test:
- A hemispherical punch applies a controlled force, and data acquisition records displacement, energy, and load curves.
Typical Procedure
- Specimen Preparation:
- Specimens are cut and conditioned per test standard requirements (notched or unnotched).
- The sample is placed in a fixed support fixture based on test type.
- Instrument Calibration:
- Pendulum Calibration: Ensuring impact energy is accurately measured.
- Load & Displacement Calibration: For instrumented impact tests.
- Impact Testing:
- The pendulum, dart, or striker is released.
- The impact force, displacement, and energy absorption are measured.
- Data Collection & Analysis:
- Pendulum Impact: Break type, impact strength.
- Dynatup & Falling Dart: Load-deflection curves, failure energy, deflection at failure.
- Multiaxial Punch: Time-dependent energy dissipation, load-displacement behavior.
Specimen Types
Specimens used by DatapointLabs in various types of impact testing are as follows:
| Specimen Type | DatapointLabs Test IDs |
|---|---|
| Notched Izod Specimens [Details] | M-425 |
| Notched Charpy Specimens [Details] | M-427 |
| Impact Plaques [Details] | M-410, M-412, M-411 |
Extensometry Techniques
Extensometry techniques typically employed by DatapointLabs in various types of creep testing are as follows:
| Extensometry Technique | DatapointLabs Test IDs |
|---|---|
| Not Relevant | M-425, M-427 |
| Drop Tower Load Cell Accelerometer | M-410, M-412 |
| Crosshead Displacement (Axial) | M-411 |
Characterization Measurements
Izod Pendulum Impact (ASTM D256, ISO 180, ASTM D4812)
- Break Type: Complete Break (CB), Partial Break (PB), or No Break (NB).
- Impact Resistance: Energy absorbed per unit thickness.
Charpy Pendulum Impact (ASTM D6110, ISO 179)
- Break Type: Brittle or ductile fracture characterization.
- Impact Strength: Energy absorbed per unit cross-section.
Dynatup Instrumented Impact (ASTM D3763, ISO 6603-2)
- Deflection at Maximum Load: Maximum displacement before fracture.
- Energy at Maximum Load: Peak energy absorbed at the highest load.
- Failure Type: Crack initiation, complete failure, or plastic deformation.
- Maximum Load: Peak force before rupture.
- Total Energy: Overall energy dissipated during impact.
Falling Dart Uninstrumented Impact (ASTM D3763, ISO 6603-1)
- Deflection at Maximum Load: Vertical displacement at peak force.
- Energy at Maximum Load: Energy required to cause initial crack propagation.
- Failure Type: Ductile failure (yielding) or brittle failure (crack propagation).
- Maximum Load: Peak force sustained before rupture.
- Total Energy: Full energy absorbed before complete material failure.
Low-Speed Multiaxial Punch (ASTM D3763, ISO 6603-2)
- Deflection at Maximum Load: Maximum deformation at peak load.
- Displacement vs. Time Plot: Graph of displacement response over time.
- Energy and Load vs. Deflection Curves: Graphs illustrating the relationship between energy, load, and material deflection.
- Energy and Load vs. Time Curves: Graphs depicting energy absorption and load application over time.
- Energy at Maximum Load: Total energy absorbed by the specimen at peak load.
- Energy vs. Deflection Curves: Graphs of correlation between absorbed energy and material deflection.
- Energy vs. Time Curves: Graphs of energy absorption behavior over time.
- Failure Type: The mode of specimen failure (e.g., brittle fracture, ductile failure).
- Load vs. Displacement Plot: Graph of relationship between applied load and material displacement.
- Maximum Load: Highest force exerted on the specimen before failure.
- Total Energy: The overall energy absorbed by the specimen.
Typical Data Reported (see test descriptions for exact details)
- Impact Energy: Overall energy dissipated during impact.
- Impact Resistance or Toughness: Ability to absorb energy before fracturing.
- Load vs. Deflection Curves: Graphs illustrating the relationship between load and deflection.
- Break Type: Classified as brittle, ductile, partial, complete.
- Fracture Energy Absorption: Overall energy absorbed prior to fracture.
- Time-Resolved Load & Energy Data: For low-speed multiaxial punch test.
Suitable Material Types
- Polymers & Composites: Toughness evaluation for structural applications.
- Metals & Alloys: Fracture mechanics and fatigue studies.
- Elastomers: Energy dissipation in shock-absorbing materials.
- Glass & Ceramics: Crack initiation and failure behavior.
Suitable Applications
- Automotive & Aerospace: Crashworthiness, bumper and panel impact resistance.
- Consumer Goods & Packaging: Drop impact testing for plastic containers.
- Medical Devices: Durability of prosthetics under sudden loads.
- Construction & Safety Equipment: Helmet and safety barrier impact analysis.
Conclusion
Impact testing using pendulum, instrumented drop, and multiaxial impact methods provides critical data on material toughness, fracture behavior, and energy dissipation. These standardized methods – reflected in ASTM D256, ISO 180, ASTM D4812, ASTM D6110, ISO 179, ASTM D3763, and ISO 6603 – allow engineers to design safer, more durable materials for high-impact applications in automotive, aerospace, consumer products, and structural engineering.
