Introduction to physical polymer science

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. To fit functional demand, materials with desired physical, chemical, biological, biomechanical, and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

Biomedical applications of biodegradable polymers

Two-component ordered structures in which both phases are solid and continuous (co-continuous solid structures) are un usual in nature and in commercial applications. Natural and synthetic co-continuous structures, comprised of hard and soft materials can provide outstanding combinations of properties including stiffness, strength, impact resistance, toughness, and energy dissipation. [ 1 , 2 ] The geometric and topological arrangement of the constituents provides avenues to engineer the macroscale properties. Various chemical processing routes and technologies now enable the precise production of ordered co-continuous microstructured materials over a wide range of length scales. For example, block copolymer chemistry can be tailored to provide periodic bi-continuous structures with feature size of sub-micrometer [ 3 ] while immiscible polymer blends can yield random bi-continuous structures. [ 4 ] Solid cocontinuous microstructures in other material systems have also been of recent interest, including metal-ceramic composites [ 5 ]

Co-Continuous Composite Materials for Stiffness, Strength, and Energy Dissipation

Ballistic impact mechanisms – A review on textiles and fibre-reinforced composites impact responses

Ballistic impact response of Kevlar® reinforced thermoplastic composite armors

Ballistic Resistant Body Armor: Contemporary and Prospective Materials and Related Protection Mechanisms

Ballistic helmets – Their design, materials, and performance against traumatic brain injury

The ballistic impact of Twaron CT709® plain weave fabrics is studied using a three-dimensional fabric model. The model is developed by treating each individual yarn as a continuum, and the time-dependent yarn behavior is phenomenologically described using a three-dimensional linear viscoelastic constitutive relation. A user subroutine VUMAT for ABAQUS/Explicit is compiled to incorporate the constitutive behavior. By using the newly developed model, a parametric study is carried out to analyze the effects of various parameters on the impact behavior of the fabrics, which include impact velocity, inter-yarn friction, and the number of fabric layers. The simulation results obtained include bullet residual velocity, fabric deformation and damage pattern, kinetic energy of the system, fabric strain energy, and frictional dissipation energy. The residual velocities predicted by the current model correlate well with existing experimental data, and the parametric study leads to the determination of the optimal nu...

Ballistic Impact of Twaron CT709® Plain Weave Fabrics

Protecting a soldier’s head from injury is critical to function and survivability. Traditionally, combat helmets have been utilized to provide protection against shrapnel and ballistic threats, which have reduced head injuries and fatalities. However, home-made bombs or improvised explosive devices (IEDs) have been increasingly used in theatre of operations since the Iraq and Afghanistan conflicts. Traumatic brain injury (TBI), particularly blast-induced TBI, which is typically not accompanied by external body injuries, is becoming prevalent among injured soldiers. The responses of personal protective equipment, especially combat helmets, to blast events are relatively unknown. There is an urgent need to develop head protection systems with blast protection/mitigation capabilities in addition to ballistic protection. Modern military operations, ammunitions, and technology driven war tactics require a lightweight headgear that integrates protection mechanisms (against ballistics, blasts, heat, and noise), sensors, night vision devices, and laser range finders into a single system. The current article provides a comparative study on the design, materials, and ballistic and blast performance of the combat helmets used by the US Army based on a comprehensive and critical review of existing studies. Mechanisms of ballistic energy absorption, effects of helmet curvatures on ballistic performance, and performance measures of helmets are discussed. Properties of current helmet materials (including Kevlar K29, K129 fibers and thermoset resins) and future candidate materials for helmets (such as nano-composites and thermoplastic polymers) are elaborated. Also, available experimental and computational studies on blast-induced TBI are examined, and constitutive models developed for brain tissues are reviewed. Finally, the effectiveness of current combat helmets against TBI is analyzed along with possible avenues for future research.

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Ballistic helmets - Their design, materials, and performance against traumatic brain injury

Ballistic helmet is a standard infantry equipment that provides ballistic protection from fragmenting to the head, temples, ear and neck of the wearer. This paper presents the study of the design of a locally used ballistic helmet, i.e. Personnel Armor System for Ground Troop (PASGT) type helmet, from ergonomic perspectives and the identification of potential risk areas of injury based on the current ballistic helmet design. Two quantitative assessment techniques are employed in the investigation. First, a set of questionnaires were distributed to the current users of the PASGT helmet. The result showed that the 54.8% of respondents experienced pain on the parietal (top) area of their head, which is a potential risk area of head injury. Second, an experiment with 10-mm thick sponge layer added to the interior part of the helmet was conducted to test its effect on the contact pressure between the head of the wearer and the medium size PASGT helmet while jogging on a treadmill at 8 km/h for 180 seconds. Mean of peak contact pressure with and without wearing the sponge of 2.5 kPa and 2.6 kPa, respectively, are obtained from the practical test. The maximum of peak contact pressure is found to be 3.6 kPa with the sponge and 4.2 kPa without the sponge. The results obtained in this study indicate that there are areas of discomfort interior to the PASGT helmet in contact with the wearer and that the discomfort can be minimized by appending a sponge layer to the frontal of the helmet.

N. V. David

Papers

Ballistic Resistant Body Armor: Contemporary and Prospective Materials and Related Protection Mechanisms

Ballistic helmets – Their design, materials, and performance against traumatic brain injury

Ballistic Impact of Twaron CT709® Plain Weave Fabrics

Ballistic helmets - Their design, materials, and performance against traumatic brain injury

An Ergonomic Study of a Conventional Ballistic Helmet