Mechanical properties of unidirectional continuous fiber self‐reinforced polyethylene graded laminates

The aim of this study is to prepare of self‐reinforced polyethylene graded composite laminates (SrPEGCL) by adopting both concepts of “graded” and “self‐reinforced” and analyze their mechanical properties under tensile loading. Three different kinds of fiber volume fractions were employed to prepare continuous fiber unidirectional symmetry SrPEGCL with two graded directions. Tensile experiments were carried out to investigate tensile properties of SrPE composites in longitudinal, transverse, and 45‐bias direction. The microscopic failure mechanism of SrPEGCL were studied and observed by Scanning Electron Microscope (SEM). Laminate stress analysis with ply‐by‐ply discount method was adopted to investigate the damage mechanism using failure criteria and parallel spring model. Observations and conclusions about the effect of graded structure and graded direction on mechanical properties of SrPEGCL under tensile loading were discussed. Compared to common self‐reinforced polyethylene composites, SrPEGCL with the same or even less overall fiber volume fraction exhibited 10–20% higher tensile strength under longitudinal, transverse and 45‐bias loading direction, while graded direction had an effect on the mechanical strength of SrPEGCL as well. POLYM. COMPOS., 36:128–137, 2015. © 2014 Society of Plastics Engineers