Examining the Relationship Between Ballistic and Structural Properties of Lightweight Thermoplastic Unidirectional Composite Laminates
Abstract : The pursuit for lightweight personal protection (helmets, body armor, etc.) has been a key issue for the Army in recent years. Previous efforts have shown that the variation of orientation and architecture in ultra-high molecular weight polyethylene (UHMWPE) composite panels can significantly affect ballistic performance characteristics. In our experiments, an architecture now referred to as ARL X Hybrid emerged as the clear leader in the compromise between ballistic performance and back face deformation (BFD). For this work, thermoplastic unidirectional materials (both aramid and polyethylene based) were evaluated using 17 grain FSP V50 and 9 mm BFD testing in both typical ([0 deg/90 deg]) and X Hybrid architectures, at an areal density target 27% lighter (7.8 kg/sq m) than the currently fielded state of the art. Digital Image Correlation (DIC) was employed to characterize the materials during testing and to help elucidate the panel response as a function of architecture. Polyethylene materials in the X Hybrid architecture were shown to retain 96-99% of the [0 deg/90 deg] architecture's V50 ballistic performance, while also reducing the BFD by 36-41%. Higher fiber involvement, increased interaction area, and increased membrane stress and through-thickness compression are proposed as factors for this phenomenon.
Ballistic impact into fabric and compliant composite laminates
The development of tough, high-strength, high-modulus fibers has led to the use of fabrics and compliant composite laminates for a number of impact-related applications, such as turbine blade containment, fuselage protection and body armor. Numerous studies have been conducted to identify material properties and system mechanisms that are important to the performance of these ballistic textiles. The current paper presents a review of the factors that influence ballistic performance; specifically, the material properties of the yarn, fabric structure, projectile geometry and velocity, far field boundary conditions, multiple plies and friction. Each physical mechanism is described in detail, and original references are cited to allow further investigation.
Local public health agency performance and community health status.
This study describes the results of an analysis of the relationship between local public health agency performance and health outcomes. Findings support the model that local public health agency performance affects community health status, and depending on the outcome, performance contributions vary. New hypotheses are offered that could help determine how system performance affects health outcomes.