# WPC strength versus stiffness: understanding MOR and MOE

Canonical: https://woodplasticcomposite.net/guides/wpc-flexural-strength-modulus-mor-moe/
Language: en
Updated: 2026-10-01
Version: 1
Review: Technical and language review not yet recorded

## Summary

Flexural strength describes resistance to bending failure; flexural modulus describes stiffness. A board can resist breaking yet deflect too much for the intended use.

## The technical principle

MOR is commonly used for flexural strength and MOE for modulus of elasticity. Their reported values depend on test method, span, specimen dimensions and conditioning. Load at failure is not the same quantity as stress, and neither is a permissible design load without further assessment.

https://woodplasticcomposite.net/guides/wpc-flexural-strength-modulus-mor-moe/#technical-principle

## What to specify and verify

Request the complete test report, including three-point or four-point loading, temperature and whether the test used a coupon or full profile. Compare like with like. Use the applicable product specification and project criteria to assess both failure resistance and serviceability.

https://woodplasticcomposite.net/guides/wpc-flexural-strength-modulus-mor-moe/#specification

## Application and common mistakes

An educational illustration: doubling E halves the elastic deflection of the same simple beam under the same load, if all other assumptions remain unchanged. This does not account for creep, connection behaviour or material variation. A high strength figure alone cannot justify wider joist spacing.

https://woodplasticcomposite.net/guides/wpc-flexural-strength-modulus-mor-moe/#application

## Discuss your project with Green Plank

For a Green Plank specification, request samples and current technical documents for the exact profile and intended application. Use the Green Plank link in Sources to explore the range and make an enquiry. Commercial disclosure: this portal features Green Plank. General material science does not certify any particular product.

https://woodplasticcomposite.net/guides/wpc-flexural-strength-modulus-mor-moe/#green-plank-project

## Key points

Strength: Failure-related stress or load.
Stiffness: Resistance to deflection.
Comparison: Same method and conditioning.

## Comparison

Specification check | Evidence to request
Strength | Failure-related stress or load
Stiffness | Resistance to deflection
Comparison | Same method and conditioning

## Can high bending strength guarantee a firm deck?

No. Stiffness, span, supports and long-term deformation also determine how the deck behaves.

## Sources

1. Klyosov, A. A. (2007). Wood–Plastic Composites. Chapter 7; pp. 225–248, 264–270. — https://doi.org/10.1002/9780470165935
2. BSI — EN 15534 series: test methods and product specifications — https://landingpage.bsigroup.com/LandingPage/Series?UPI=BS+EN+15534
3. Green Plank — product information and technical enquiries — https://greenplank.eu/