When is easy: You should perform solar testing if your product will be exposed to sunlight.
Which test is more difficult to answer. There are several different types of solar tests.
One of the more popular ones is MIL-STD-810G, Method 505.5. At 15 pages with an additional 15 pages of annexes (3 of them), the specification is detailed. This section of the standard serves two purposes:
- Determine heating effects from sunshine impinging directly on equipment (Procedure I)
- Identify material degradation from sunshine (Procedure II)
Procedure 1 is primarily a heating effect test and is usually performed with halogen lamps following a diurnal cycle profile. The potential impact of solar radiation heating effects include:
- Jamming or loosening of moving parts
- Changes in strength and elasticity
- Loss of seal integrity
- Changes in electrical or electronic components
- Premature actuation of electrical contacts
- Changes in characteristics of elastomers and polymers
- Blistering, peeling, and de-lamination of paints, composites, and surface laminates
- Softening of potting compounds
- Weakening of solder joints and glued parts
Procedure 2 is a combination actinic and heating effects test using full spectrum lamps. Material effects of solar radiation, primarily from UV exposure, include:
- Fading of fabric and plastic color
- Break down and fading of paints
- Deterioration of natural and synthetic elastomers and polymers through photochemical reactions initiated by shorter wavelength radiation (especially acute for high strength polymers such as Kevlar)
As with other 810G Methods, 505.5 is a general outline and it is left to the end user to create a test plan to align the test with the anticipated environment.
Following are additional popular solar testing standards, both of which MET Laboratories is accredited for:
ASTM G154 – This test consists of exposing samples to 42 cycles of 8 hours of UVA-340 ultraviolet light at 60°C, followed by 4 hours of condensation (mimicking dew) at 50°C. Overall, this test involves 21 days of exposure.
ASTM G155 – In this test, xenon arc lamps simulate full-spectrum sunlight within a controlled test chamber. Because xenon arc light is most similar to natural sunlight, this standard is often used for outdoor weatherization testing.
MET Labs performs fully-accredited MIL-STD-810 Method 505.5 solar testing along with ASTM G154 and ASTM G155 testing. We also work with customers to develop custom test plans to meet special requirements.