# Reading WPC mechanical data: strength, stiffness and impact

Canonical: https://woodplasticcomposite.net/guides/wpc-mechanical-properties-strength-modulus-impact/
Language: en
Updated: 2026-10-16
Version: 1
Review: AI-assisted English article. Human technical review has not been recorded.

## Summary

Strength describes resistance to a defined failure condition; stiffness describes resistance to deformation. A strong small specimen does not automatically establish a suitable structural profile.

## Translate the terminology

Tensile tests load a specimen in tension. Flexural tests bend it. MOR commonly denotes modulus of rupture, a bending-strength measure, while MOE denotes modulus of elasticity, a stiffness measure. Compression describes another loading condition. Impact tests such as Izod and Charpy introduce their own specimen and loading arrangements.

See the comparison table below for translate the terminology.

https://woodplasticcomposite.net/guides/wpc-mechanical-properties-strength-modulus-impact/#translate-the-terminology

## Do not merge impact numbers

Wood/PP research found different particle-size trends for notched and unnotched impact. This illustrates why impact results require their exact test description. An instrumented-impact study of kenaf/PP provides another example of investigating impact behaviour in a specific composite system. [R20,R48]

https://woodplasticcomposite.net/guides/wpc-mechanical-properties-strength-modulus-impact/#do-not-merge-impact-numbers

## Specify the evidence chain

The EN 15534 family connects compound and product characterization with particular end uses. Its existence does not mean that citing the standard number proves compliance. 

For a public walkway, request the tested board identity, support arrangement and relevant acceptance criteria. For a new compound, request the number of specimens and variability as well as the mean. Keep initial laboratory properties separate from conditioned values and design values.

This approach lets architects compare products on evidence rather than a single impressive number selected from a datasheet.

https://woodplasticcomposite.net/guides/wpc-mechanical-properties-strength-modulus-impact/#specify-the-evidence-chain

## Evidence and source scope

[1] Official standards catalogue; scopes, not full normative text.

[2] Experimental study; official abstract.

[3] Experimental study.

https://woodplasticcomposite.net/guides/wpc-mechanical-properties-strength-modulus-impact/#evidence-scope

## Key points



## Comparison

Reported property | Essential comparison detail
Tensile strength | Specimen geometry, direction and conditioning
Flexural strength or MOR | Span, section and test procedure
Flexural modulus or MOE | Calculation method and conditions
Impact result | Test type, notch and units



## Sources

1. EN 15534 standards series; BSI — https://landingpage.bsigroup.com/LandingPage/Series?UPI=BS+EN+15534
2. Effects of wood fiber characteristics on mechanical properties of wood/polypropylene composites; Stark and Rowlands — https://research.fs.usda.gov/treesearch/8558
3. Instrumented Impact Testing of Kenaf Fiber Reinforced Polypropylene Composites — https://research.fs.usda.gov/download/treesearch/32710.pdf