A new test set-up for skull fracture characterisation.
ABSTRACT Skull fracture is a frequently observed type of severe head injury. Historically, a variety of impact test set-ups and techniques have been used for investigating skull fracture. The most frequently used are the free-fall technique, the guided fall or drop tower set-up and the piston-driven impactor set-up. This document proposes a new type of set-up for cadaver head impact testing which combines the strengths of the most frequently used techniques and devices. The set-up consists of two pendulums, which allow for a 1 degree of freedom rotational motion. The first pendulum is the impactor and is used to strike the blow. The head is attached to the second pendulum using a polyester resin. Local skull deformation and impact force are measured with a sample frequency of 65 kHz. From these data, absorbed energy until skull fracture is calculated. A set-up evaluation consisting of 14 frontal skull and head impact tests shows an accurate measurement of both force and local skull deformation until fracture of the skull. Simplified mechanical models are used to analyse the different impacting techniques from literature as well as the new proposed set-up. It is concluded that the proposed test set-up is able to accurately calculate the energy absorbed by the skull until fracture with an uncertainty interval of 10%. Second, it is concluded that skull fracture caused by blunt impact occurs before any significant motion of the head. The two-pendulum set-up is the first head impact device to allow a well-controlled measurement environment without altering the skull stress distribution.
- SourceAvailable from: PubMed Central[Show abstract] [Hide abstract]
ABSTRACT: In order to replicate the fracture behavior of the intact human skull under impact it becomes necessary to develop a material having the mechanical properties of cranial bone. The most important properties to replicate in a surrogate human skull were found to be the fracture toughness and tensile strength of the cranial tables as well as the bending strength of the three-layer (inner table-diplöe-outer table) architecture of the human skull. The materials selected to represent the surrogate cranial tables consisted of two different epoxy resins systems with random milled glass fiber to enhance the strength and stiffness and the materials to represent the surrogate diplöe consisted of three low density foams. Forty-one three-point bending fracture toughness tests were performed on nine material combinations. The materials that best represented the fracture toughness of cranial tables were then selected and formed into tensile samples and tested. These materials were then used with the two surrogate diplöe foam materials to create the three-layer surrogate cranial bone samples for three-point bending tests. Drop tower tests were performed on flat samples created from these materials and the fracture patterns were very similar to the linear fractures in pendulum impacts of intact human skulls, previously reported in the literature. The surrogate cranial tables had the quasi-static fracture toughness and tensile strength of 2.5 MPa√ m and 53 ± 4.9 MPa, respectively, while the same properties of human compact bone were 3.1 ± 1.8 MPa√ m and 68 ± 18 MPa, respectively. The cranial surrogate had a quasi-static bending strength of 68 ± 5.7 MPa, while that of cranial bone was 82 ± 26 MPa. This material/design is currently being used to construct spherical shell samples for drop tower and ballistic tests.Frontiers in Bioengineering and Biotechnology 01/2013; 1:13.
- [Show abstract] [Hide abstract]
ABSTRACT: The aim of this study was to analyze the occurrence and characteristics of orbital roof fractures, periorbital hematoma, conjunctival hemorrhage, orbital roof discoloration, and concomitant head injuries in falls from a standing height.Forensic Science Medicine and Pathology 07/2014; · 1.96 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Blunt force trauma forms a substantial portion of deaths worldwide. However, few studies have attempted to determine the force involved with blunt force trauma to the lateral part of the head. Nor have many studies been conducted at velocities exceeding 10m/s. The acquisition of human tissue for experimental studies is becoming increasingly difficult. As such, the current study investigates the trauma and the force involved with cranial blunt force trauma in a porcine model. Thirty whole porcine heads were subjected to single impact tests on the fronto-parietal region at velocities ranging from 10m/s to 25m/s. Half the specimens were subjected to impact by a short projectile resembling a hammer head and the other half were subjected to impact with a Hopkinson pressure bar (HPB). Both implements had the same impact diameter and were machined from the same material. The HPB is an apparatus commonly used in material testing. Its use to determine fracture force in whole cranial specimens is novel. Fractures appeared similar in both the hammer tests and HPB tests. Lacerations and fractures resembled the shape of the striker surface with the most common fracture observed being a semi-circular depressed fracture. The mean peak fracture force was 7760N (±4150N), with a mean displacement of 3.1mm (±1.1mm). Peak fracture forces concur well with previous studies although no clear trend appears to exist between level of trauma and peak impact force.Legal medicine (Tokyo, Japan). 08/2014;