What is Hail Impact Testing?
Hail impact testing is an environmental durability test used to evaluate a material or product’s ability to withstand the mechanical forces produced by falling hailstones. The test typically uses propelled ice balls of specified size and velocity to simulate hail impacts and assesses physical damage, deformation, cracking, penetration, or loss of function.
What Was the Client Looking to Evaluate?
The project testing was designed to evaluate how well cellulose cooling pads and heat transfer coils resist hail damage. Using a compressed air launcher, ice spheres ranging from 1 to 2.5 inches in size were fired at test units at specific impact angles of 15°, 30°, and 45° and controlled velocities.
The objective was to evaluate surface damage, penetration depth, and structural impact, and to generate reliable data to determine whether damaged units could be repaired in the field.
What Were the Testing Challenges?
Challenge 1: Lack of a Detailed Initial Scope of Work
The client reached out to the Matestlab Inc. team to manage the testing. Because the initial discussions went smoothly, the project was started based on informal alignment rather than a detailed initial Scope of Work (SOW).
Challenge 2: Misalignment During Test Setup
Early in the project, the client visited our partner facility, toured the laboratory, and discussed the setup with the lab team. The team assumed that the testing requirements were fully aligned.
Challenge 3: Incomplete Test Report and Data
The issue became apparent when the first test report was received . The report was missing several important details, including:
- Exact impact locations and radii were unconfirmed.
- Photo logs were incomplete.
- Penetration depths were not tabulated.
- The report lacked a clear summary rating framework.
- The laboratory performed single impacts at each location, whereas the client expected up to three repeated strikes at the same location to evaluate cumulative damage.
Because the report could not provide the information needed to determine whether damaged units could be repaired in the field, the client placed the project on hold.
The Customized Testing Approach by Matestlab
To address the issues and ensure full alignment, the Matestlab team held alignment calls with the client and the laboratory analysts to document each testing requirement.
Based on these discussions, a detailed SOW was prepared covering the following requirements:
1. Impact Parameters
A clear testing matrix was established covering:
- Ice sphere sizes: 1″, 1.5″, 2″, and 2.5″
- Controlled impact velocities
- Impact angles: 15°, 30°, and 45°
- Exact impact radii and locations
2. Test Logs
Structured test tables were established to record:
- Date and time
- Ice sphere size
- Impact angle
- Hit count
- Pad depth
- Coil depth
- Field notes
3. Damage Ratings
A standardized damage classification system was established:
- N – No damage
- C – Surface damage
- P – Full penetration
The classification approach was based on standards such as NBS 9871.
4. Photographic Documentation
Labeled photographs were required and linked directly to the corresponding entries in the testing data tables to provide traceable visual documentation of the test results.
A Balanced Testing Plan
The team conducted a retest; the client reviewed and signed off on the updated SOW. The team then executed all 36 required impacts, recording the requested depth measurements, testing metrics, and photographs according to the newly established requirements.
What Were the Analysis Results and Interpretation?
The completed testing generated the detailed impact and damage information the client required, including the specified impact parameters, depth measurements, hit counts, damage classifications, and corresponding photographic documentation.
The updated report provided a structured representation of the test results, allowing the client to use the data to support decisions regarding whether damaged units could be repaired in the field.
Discussion and Conclusions
The updated testing and reporting approach successfully addressed the gaps identified in the initial report. After reviewing the revised report, the client confirmed that it was significantly improved and that the data provided the information needed to support field repair decisions for its clients. The project also highlighted the importance of establishing complete technical alignment before testing begins. Verbal agreements and high-level assumptions can create differences in expectations about test parameters, documentation, and reporting requirements.
FAQs
Why is hail damage resistance evaluation necessary?
Hail-resistance evaluation verifies whether cellulose cooling pads and heat-transfer coils can withstand hail impacts while maintaining their physical integrity, airflow, heat-transfer capability, and service life.
How was hail impact simulated?
A compressed-air launcher fired ice spheres at the test units at controlled velocities and specified impact angles.
What damage classifications were used?
The standardized classifications were N (no damage), C (surface damage), and P (full penetration).
