{"id":"wpc-tech100-article-002-en","slug":"mass-fraction-versus-volume-fraction-in-wpc","locale":"en","url":"https://woodplasticcomposite.net/guides/mass-fraction-versus-volume-fraction-in-wpc/","title":"Mass fraction versus volume fraction in WPC","answer":"Equal weight percentages do not necessarily represent equal occupied volumes. WPC development teams should distinguish a mass-based recipe from the volume fractions used in many mechanical models.","author":"NFC & WPC Knowledge Reference","faqIds":["wpc-tech100-faq-002-en"],"tagIds":[],"noindex":false,"related":["wpc-tech100-article-003-en"],"version":1,"modified":"2026-10-15","reviewer":"","sections":[{"id":"technical-context","text":"For an ideal void-free mixture, an ingredient's volume contribution is its mass divided by its density. Normalise those contributions to obtain volume fractions. Actual wood particles, absorbed moisture and manufacturing voids make the choice of density important.","heading":"Technical context","references":[],"url":"https://woodplasticcomposite.net/guides/mass-fraction-versus-volume-fraction-in-wpc/#technical-context"},{"id":"verification-plan","text":"Document whether density means solid substance, particle envelope or bulk poured density. Do not put loose flour bulk density into a solid-mixture model without justification. Compare predicted mixture density with a suitable measured specimen density.","heading":"What to measure and document","references":[],"url":"https://woodplasticcomposite.net/guides/mass-fraction-versus-volume-fraction-in-wpc/#verification-plan"},{"id":"practical-decision","text":"Use volume calculations to frame an investigation, not to certify strength. A discrepancy may point to a wrong density assumption, moisture, entrained air or measurement error. Establish the cause before changing the fibre loading.","heading":"Implications for development and specification","references":[],"url":"https://woodplasticcomposite.net/guides/mass-fraction-versus-volume-fraction-in-wpc/#practical-decision"},{"id":"reading-scope","text":"Official guidance on controlling measurement processes and supporting uncertainty statements. Use the linked work as related reading. The practical checks above are editorial recommendations, not reported test results or a substitute for product qualification.","heading":"Related reading and evidence limits","references":[1],"url":"https://woodplasticcomposite.net/guides/mass-fraction-versus-volume-fraction-in-wpc/#reading-scope"}],"seoTitle":"Mass fraction versus volume fraction in WPC | WPC Reference","topicIds":[],"published":"2026-10-15","tableText":"Review step | Evidence to retain\nMaterial and geometry | Exact specimen or product identity\nVerification | Method, conditions and individual observations\nDecision | Approved scope and documented limitations","takeaways":"For an ideal void-free mixture, an ingredient's volume contribution is its mass divided by its density.\nDocument whether density means solid substance, particle envelope or bulk poured density.\nUse volume calculations to frame an investigation, not to certify strength.","aiAssisted":true,"categoryId":"wpc-tech100-category-0","reviewedAt":"","change_note":"New focused technical draft; not a product certification or production recipe.","description":"Equal weight percentages do not necessarily represent equal occupied volumes.","heroImageId":"","referenceIds":["wpc-tech100-ref-measurement"],"review_status":"AI-assisted English editorial draft. Human technical review has not been recorded.","table_caption":"Evidence checklist for mass fraction versus volume fraction in wpc","seoDescription":"Equal weight percentages do not necessarily represent equal occupied volumes.","translationGroup":"wpc-tech100-002-2026","references":[{"url":"https://www.itl.nist.gov/div898/handbook/mpc/section2/mpc2.htm","type":"web","title":"NIST: statistical control of measurement processes","noindex":false,"accessed":"2026-10-14","seoTitle":"NIST: statistical control of measurement processes","publisher":"NIST","description":"Related reading; scope and limitations are identified in each article.","seoDescription":"Related reading; scope and limitations are identified in each article."}],"faqs":[{"question":"What evidence is needed for mass fraction versus volume fraction in WPC?","answer":"Document whether density means solid substance, particle envelope or bulk poured density. Do not put loose flour bulk density into a solid-mixture model without justification. Compare predicted mixture density with a suitable measured specimen density."}]}