Moisture Absorption & Material Degradation Calculator — Modulus and Strength Loss Analyzer
Calculate moisture content, effective modulus, and effective strength using relative humidity, temperature, exposure time, thickness, and initial material properties.
Enter the known values and review the calculated result
Input parameters
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Material
Environment
Geometry
Initial material properties
Results
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Method, application and limitations
Review the calculation method, intended application and engineering assumptions before using the result in a design decision.
Formula and calculation method
moisture content formula:
RH = humidity / 100
temperature factor = exp(0.03 · (temperature − 23))
diffusion factor = material diffusion coefficient · temperature factor
diffusion time constant = thickness² / diffusion factor
exposure-to-diffusion ratio = exposure time / diffusion time constant
saturation factor = 1 − exp(−exposure-to-diffusion ratio)
effective saturation moisture = material saturation moisture · RH
degradation ratio = effective saturation moisture · saturation factor
M = degradation ratio · 100
effective modulus formula:
E = max(0, E0 · (1 − material modulus degradation coefficient · degradation ratio))
effective strength formula:
σ = max(0, σ0 · (1 − material strength degradation coefficient · degradation ratio))
where:
- M — moisture content (%)
- E — effective modulus (Pa)
- σ — effective strength (Pa)
- RH — relative humidity ratio (–)
- humidity — relative humidity (%)
- temperature — exposure temperature (°C or converted temperature input)
- exposure time — time exposed to humidity (s or converted time input)
- thickness — material thickness (m or converted length input)
- E0 — initial modulus (Pa)
- σ0 — initial strength (Pa)
- material diffusion coefficient — moisture diffusion coefficient from selected material data
- material saturation moisture — saturation moisture from selected material data
- material modulus degradation coefficient — modulus degradation coefficient from selected material data
- material strength degradation coefficient — strength degradation coefficient from selected material data
When to use this calculator
When to use this calculator:
- Estimate moisture content after a defined humidity, temperature, exposure time, and thickness condition.
- Calculate effective modulus after moisture-related material degradation.
- Calculate effective strength after moisture-related material degradation.
- Check whether exposure time is short enough to create moisture gradient risk.
- Evaluate whether high temperature accelerates moisture-related degradation.
- Compare initial material properties against retained stiffness and retained strength after exposure.
How to interpret the result
Moisture content is defined as the percentage form of the degradation ratio caused by relative humidity, temperature-dependent diffusion, exposure time, thickness, and material saturation moisture.
Effective modulus is defined as the initial modulus reduced by the material modulus degradation coefficient and degradation ratio. Effective strength is defined as the initial strength reduced by the material strength degradation coefficient and degradation ratio.
Moisture content increases with relative humidity and exposure time. Increasing temperature increases the temperature factor, which increases the diffusion factor and reduces the diffusion time constant. Increasing thickness increases the diffusion time constant and can reduce the exposure-to-diffusion ratio.
- Safe — degradation ratio ≤ 0.2, strength retention ≥ 0.7, degradation ratio ≤ 0.3, and strength retention ≥ 0.5.
- Limit — degradation ratio > 0.2, while degradation ratio ≤ 0.3 and strength retention ≥ 0.7.
- Warning — degradation ratio > 0.3 or strength retention < 0.7, while degradation ratio ≤ 0.5 and strength retention ≥ 0.5.
- Unsafe — degradation ratio > 0.5 or strength retention < 0.5.
- Invalid — at least one required input violates the validation rules, such as relative humidity outside 0–100%, non-positive exposure time, non-positive thickness, non-positive initial modulus, non-positive initial strength, or initial strength greater than initial modulus.
The result is used to evaluate retained stiffness, retained strength, dimensional change, moisture gradient risk, temperature acceleration, and diffusion regime after moisture exposure.
Calculation example
Example:
A user wants to estimate how much stiffness and strength remain after a material sample is exposed to humid air for a defined time.
- Relative humidity = 80%
- Temperature = 50
- Exposure time = 100000
- Thickness = 0.005
- Initial modulus = 3000000000 Pa
- Initial strength = 80000000 Pa
- Material diffusion coefficient, saturation moisture, modulus degradation coefficient, and strength degradation coefficient are taken from the selected material data.
The calculator returns moisture content, effective modulus, and effective strength from the selected material coefficients and the exposure-to-diffusion ratio.
Assumptions and limitations
- Relative humidity is converted to a 0–1 ratio before calculating effective saturation moisture.
- Temperature changes diffusion through an exponential factor equal to exp(0.03 · (temperature − 23)).
- Moisture saturation follows 1 − exp(−exposure-to-diffusion ratio).
- Effective modulus decreases linearly with degradation ratio and material modulus degradation coefficient.
- Effective strength decreases linearly with degradation ratio and material strength degradation coefficient.
- Effective modulus and effective strength are clamped to zero when degradation would produce negative values.