Impact Performance of Composite Decking

The backyard deck has taken on an ever increasing role in our lives becoming an extension of a homes interior living space. Traditionally decks have been built from pressure treated lumber, however, cost, life cycle, appearance, construction time, maintenance and environmental concerns are all factors contributing to the huge growth in the use of wood–plastic composites, also known as composite decking.

Made from a wide ranging mixture of wood and plastic, composite decking has certain advantages like durability, color retention and reduced maintenance costs over pressure treated wood. With a material cost 20 to 30 percent more than pressure treated pine, impact performance can be critical. Decks are routinely subjected to a wide range of everyday impact events, dropped tools, patio furniture, ladders and paint cans to name a few, and the types and quantities of the various materials used in the manufacturing of the decking can affect their resistance to impacts.

When approached by a manufacturer of composite decking we recommended a Instron 9450 with optional High energy system, instrumented with a 22.2kN tup, ½” hemispherical tup insert, 1” spherical tup insert, Data Acquisition System and Bluehill Impact software. By varying the tup insert and test velocity we were able to create a range of impact profiles and energies that allowed the customer to simulate a wide variety of impacts that their product might be subjected to.

The 9450 is well suited for helping customers determine the performance characteristics of their materials when subjected to an impact event. The information gathered by doing instrumented impact testing can be used to provide the customer with a data baseline whereby they can determine how changes made in the mix of raw materials will perform in real life situations. A broader range of testing could be accomplished with the inclusion of an environmental chamber to study impact characteristics at different temperatures as well as using different fixtures and inserts to simulate other unsupported spans and impact events.