Impact of high moisture conditions on the serviceability performance of wood plastic composite decks

José S. Machado, Sara Santos, Fernando F. S. Pinho, Fábio Luís, Ana Maria Martins Alves, Rita Simões, José Carlos Rodrigues

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


Wood plastic composites (WPCs) are being increasingly used as alternatives to wooden decks. In the present study, it was verified the potential loss of stiffness of WPC deck boards as a result of moisture intake. It was also assessed the importance of moisture intake in the fulfilment of serviceability limit states. For these purposes, three different types of commercial WPC decks were studied, with high (WPCH), medium (WPCM) and low (WPCL) expected mechanical performance. Different experimental designs were followed to simulate full exposure to outdoor conditions and the effect of possible internal stress due to differential shrinkage and the swelling behaviour of fibres and the matrix. The results indicate a high loss of bending modulus of elasticity due to water absorption (between 40 and 50%) and shrinkage/swelling movements (between 22 and 29%). This level of stiffness loss has a direct impact on ensuring the compliance to the serviceability limit states. A strong negative linear relationship between water absorption and the loss of bending stiffness was established, which can be a helpful tool to assist manufacturers in defining the application rules and ensuring the expected service life of their products.

Original languageEnglish
Pages (from-to)122-131
Number of pages10
JournalMaterials and Design
Publication statusPublished - 5 Aug 2016


  • Modulus of elasticity
  • Serviceability
  • Water absorption
  • WPC decks


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