At a glance
Flexural strength describes resistance to bending failure; flexural modulus describes stiffness. A board can resist breaking yet deflect too much for the intended use.
Key points
- Strength: Failure-related stress or load.
- Stiffness: Resistance to deflection.
- Comparison: Same method and conditioning.
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.
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.
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.
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.
Project specification checklist
| Specification check | Evidence to request |
|---|---|
| Strength | Failure-related stress or load |
| Stiffness | Resistance to deflection |
| Comparison | Same method and conditioning |
Common questions
Can high bending strength guarantee a firm deck?
No. Stiffness, span, supports and long-term deformation also determine how the deck behaves.
Question permalink ↗Sources & further reading
- Klyosov, A. A. (2007). Wood–Plastic Composites. Chapter 7; pp. 225–248, 264–270. ↗John Wiley & Sons · Book · 2026-10-01
- BSI — EN 15534 series: test methods and product specifications ↗BSI · Web reference · 2026-10-01
- Green Plank — product information and technical enquiries ↗Green Plank · Web reference · 2026-10-01
Cite this page
J. A. Gill. “WPC strength versus stiffness: understanding MOR and MOE” Version 1. Updated 2026-10-01. https://woodplasticcomposite.net/guides/wpc-flexural-strength-modulus-mor-moe/
Author profile
Author: J. A. Gill
WPC and natural-fibre composite specialist · Innovator, inventor, product designer and entrepreneur
Original educational article informed by Klyosov (2007). Modern project applications are editorial synthesis. This is not a product certificate or a substitute for project-specific design.
General material information is not product certification or project-specific engineering advice.
Questions & comments
Plain text only. No links, email addresses, HTML or attachments. 15–3,000 characters. All submissions require approval.
Opening the form sets a necessary, first-party cookie for up to one year so this browser can manage and delete its submissions. Names are not identity-verified. Do not share confidential or personal information.