Statistical reliability analyses of two wood plastic composite extrusion processes

Estimates of the reliability of wood plastic composites (WPC) are explored for two industrial extrusion lines. The goal of the paper is to use parametric and non‐parametric analyses to examine potential differences in the WPC metrics of reliability for the two extrusion lines that may be helpful for use by the practitioner. A parametric analysis of the extrusion lines reveals some similarities and disparities in the best models; however, a non‐parametric analysis reveals unique and insightful differences between Kaplan–Meier survival curves for the modulus of elasticity (MOE) and modulus of rupture (MOR) of the WPC industrial data. The distinctive non‐parametric comparisons indicate the source of the differences in strength between the 10.2% and 48.0% fractiles [3,183–3,517MPa] for MOE and for MOR between the 2.0% and 95.1% fractiles [18.9–25.7MPa]. Distribution fitting as related to selection of the proper statistical methods is discussed with relevance to estimating the reliability of WPC. The ability to detect statistical differences in the product reliability of WPC between extrusion processes may benefit WPC producers in improving product reliability and safety of this widely used house‐decking product. The approach can be applied to many other safety and complex system lifetime comparisons.