Measurements of Ballistic Impact Response of Novel Coextruded PC/PMMA Multilayered-Composites

Ballistic impact behavior of coextruded composites consisting of alternate layers of ductile polycarbonate (PC) and brittle poly(methyl methacrylate) (PMMA) were investigated. These PC/PMMA composites were 256, 1024, 2048 and 4096 layers; each consisted of various component compositions and their corresponding layer thickness was on the order of micron or sub-micron scale. Individual layer thickness of PMMA was determined to be critical for the impact response of these ductile/brittle hybrids. A brittle mode of failure was encountered as the thickness of PMMA layers reached 0.5 mm or higher, regardless of their composition or layer configuration. Damage zone size increased significantly as the PMMA layer thickness reduced to approximately 0.36 mm; a mixed mode of failure resulted in these PC/PMMA composites. With the PMMA layer thickness further reduced to approximately 0.14 mm, ductile deformation, which was predominant in the pure PC, occurred in these coextruded composites. Ballistic impact energy data showed that the extent of energy absorption or dissipation increased with an increase in either the PC content or the total number of layers. These results further revealed that the individual layer thickness of PMMA was the critical material parameter, and the determined impact energy values were consistently higher for the composites with PMMA layer thickness being 0.14 mm or thinner. Adhesion between the layers appeared to be very good since delamination did not occur whether these PC/PMMA composites failed in a brittle or a ductile mode.