Carbon fiber is a lightweight, strong alternative to common steel. It is used in everything from an airliner fuselages to racing-bike frames and protective cell-phone cases. Carbon fiber was invented in the United States in the late 1950s but it wasn’t until a new manufacturing process was developed at a British research center in early ’60s that carbon fiber’s strength and lightweight potential was truly realized.
Carbon fiber reinforced polymer, or CFRP, is a process of combining strands of acrylic yarn together and baking the material to 1,400 F, which activates the carbonation of the yarn, hence the term carbon fiber. Each carbon fiber has roughly 10 layers of fabric; it is placed in a heavy press, air is extracted, a chemical resin is injected under high pressure and heated again for a specific time; then the fiber is cooled and the part is formed. When the part is removed from the press, the edges are very jagged so they are trimmed and sanded. The outer layer is the product’s final color and finish, which is a dark grey or black; the parts can be painted any colour, but are often left in the original colour, which has a unique, professional high-tech look.
One of the main advantages of this material is the strength-to-weight ratio of carbon fiber after the above process is completed; the actual weight of the component is a fraction of that of the same part made of steel. This transmits into reduced weight of vehicle parts which, in turn, can result in an overall increase in fuel economy of 20 to 30 per cent; that saving really motivates the auto industry to include carbon fiber in production lines. As a result, there will be a big push in the next few years of carbon fiber and aluminum combinations mated with other lightweight materials in modern vehicles. Anywhere the manufacture can reduce weight results in better fuel economy.
Another area that has undergone change is inside the vehicle passenger compartment, where structural strength is not important but cosmetic appeal is desired. Carbon fiber, with its sleek, stylish, eye-catching look really complements the interior of even the entry-level vehicle and is well suited for door panels and handles, outer seat contours and dash parts. These components do not have to conform to structural standards and can be made slimmer, quicker and cheaper for this reason.
On the structural side of things, auto manufacturers have established methods to give carbon-fiber parts more strength in a specific direction, for example, increasing strength in a load-bearing direction, but not doing so in areas that bear less load. Developments are underway that allow for omni-directional carbon-fiber construction, which applies strength in all directions. This version of carbon-fiber association is mostly being used in the safety cell unibody chassis assembly. Another advantage as time has passed; carbon fiber reinforced polymer has proven to be very corrosion resistant; this is a very important characteristic in both the outer body panels of the vehicle and the structural makeup of the framework or safety cell.
Let’s look at one popular vehicle that uses versions of CFRP and aluminum that’s cutting edge technology. According to the engineers and stakeholders at the Beamer camp, “The new 2016 BMW fifth-generation 7 Series uses a passenger cell called a ‘Carbon Core’ to improve performance and fuel economy, which cuts the weight by 86.kilos (or 190 pounds.)”
While the BMW carbon core is not a complete carbon-fiber, reinforced plastic tub or a series of panels as is used in racecars or hybrid supercars, the BMW efficient lightweight technology combines carbon fiber with lightweight, high-strength steel, and aluminum body panels. There are some carbon-fiber brackets and stiffeners, such as the cross-member at the top of the windshield. CFRP is inside the steel roof pillars to keep the cabin intact in a rollover or severe side impact. More 7 Series body panels are now aluminum, including doors and the trunk lid. The brakes, wheels, and suspension have lightened by 15 per cent, BMW says; savings to the so-called un-sprung weight parts have a much greater effect on performance than taking the same weight out of the gearbox or seats. BMW liberally reinforces the already strong metal/aluminum passenger cell with CFRP in critical places. The 15 CFRP reinforcements include the header above the windshield, door sills, transmission tunnel, front-to-back and left-to-right roof reinforcement tubes and bows, the B-pillar between front and rear doors, the C-pillar, and rear parcel shelf.
Most of the discussion around CFRP from a rescuer’s perspective concerns actual tool use and the dust that is created when breaching or cutting into the material. Testing done by rescuers has shown that there can be a fair amount of CFRP dust when using tools such as a fine tooth reciprocating saw blade. Although each CFRP manufacturer uses different chemicals and resins to make its product, most of the material safety data sheets call to protect your airway with either a respirator or N95 particulate mask when working around CFRP airborne dust.
In discussions with the companies that make or work with CFRP, all workers have stated that when cutting, sanding or in any situation in which they are creating dust particles, they have either worn the proper PPE as mentioned above or if operating in a close environment, have done the work under a ventilation hood fan. It is my belief that rescuers should adopt these same protocols, err on the side of caution and wear N95 masks when working around the CFRP dust.
Another challenge worthy of mention is the fact that manufacturers may paint over the carbon-fiber components and thus give rescuers no indication whether the component it is steel, aluminum, or carbon fiber. The 2016 BMW7 series upper A-pillar is an example of this; the indicator in this case is the carbon-core stamp on the top of the B-pillar.
One method firefighters in the United Kingdom use to determine if a component is made of carbon-fiber material is to place a small, pocket-sized magnet on the suspected component; if the magnet doesn’t stick, the component is most likely carbon fiber or possibly aluminum, and therefore rescuers know to protect their airways accordingly with approved respiratory measures.
In terms of hydraulic rescue tools breaching CRFP material – the material is not a challenge to sever as it simply crushes the part, such as a B-pillar, with relative ease. When cutting or spreading, the material simply breaks apart into small fragments. Rescuers will have no problem cutting the material with hand tools such as reciprocating saws and air chisels; doing so would be similar to cutting fiberglass.
Most vehicle manufacturers are investigating, testing and using carbon fiber in some form or another. Ultimately, use of carbon fiber will help manufacturers meet stricter fuel-economy and crash-safety standards. The use of carbon fiber in a vehicle can significantly reduce the weight and size of the framework; this will allow engineers to design and create more passenger compartment space. Using more carbon fiber in the manufacturing process also reduces the volume of water and electricity used to build vehicle components and chassis. Advancements in carbon-fiber technology will trickle down to the mainstream, just as airbags, anti-lock brakes, and stability control have done. Staying abreast of the changes to vehicles will allow first responders to stay on the top of their game.
However, every significant MVC is potentially a crime scene, therefore it is essential that evidence can be collected. Preserving evidence is often difficult at large incidents because the first priority of emergency services is to save lives and take care of casualties. Inevitably, establishing control posts, rescuing and treating casualties, and taking steps to prevent escalation of the incident disturbs the ground at the immediate site of the incident. To prevent unnecessary destruction of evidence, incidents must be co-ordinated to protect scenes.
Traffic-collision investigators jokingly refer to first responders as evidence-eradication teams. Crucial evidence from MVC scenes is often moved or destroyed by either emergency medical personnel or firefighters who are simply performing their jobs as they have been trained to do. First responders should be aware of what is involved with traffic-collision investigations in order to, when possible, preserve evidence at crime scenes.
Traffic investigators often arrive at the scene when emergency-response crews are in cleanup mode, well after they have finished the job. Post-incident cleanup is one of the most crucial periods during which to preserve evidence. First responders can be great resources to traffic investigators by identifying the initial positions of patients in vehicles, seatbelt use, road and weather conditions, and providing details about how the scene was found and what was moved. With data from the rescuers, investigators can document the original position of physical evidence.
Scene preservation for evidence collection is needed to:
- Ensure that any evidence is not contaminated. Physical evidence must be protected from accidental or intentional alteration from the time it is first discovered to its ultimate disposition at the conclusion of an investigation;
- Help in establishing the cause of an incident;
- Gather information to prevent a further incident from occurring;
- Accurately identify and assess the damage attributable to the incident.
There are two principle types of errors that damage scenes under investigation: commission and omission.
Errors of commission: occur when emergency personnel destroy existing evidence or add evidence. Examples are:
- Smearing fingerprints on the steering wheel, seatbelts, inner-door handles
- Stepping on evidence of skid marks, alcohol containers
- Adding your own fingerprints on the steering wheel, inner-door handles
- Rearranging the scene, such as picking up a cell phone from the floor of the vehicle
- Failure to notice odours
- Failure to listen to occupants or persons standing near the scene discussing the event
- Failure to take efforts to protect existing evidence that may otherwise be destroyed
- Failure to notice unusual actions or behaviours
When should first responders expect an MVC investigation? According to protocols, MVC investigations will occur when death or serious injury is expected, imminent or known to exist, someone has fled the scene and injury or death has occurred, an involved driver is believed to be intoxicated or under the influence of alcohol or drugs, the incident is major and of an unusual nature (coach bus, school bus, train), or the collision involves hazardous materials.
First-arriving crews should:
- Make mental notes about the scene upon arrival.
- Take note of weather conditions, heat, cold, light dark/dusk, smells, noise.
- Make a note or inform an investigator if you need to move something such as a vehicle or pole and include it in the report.
- Move vehicles and debris only if a real potential danger exists.
- Disturb the scene as little as possible.
- Take photos or have a higher-ranking officer take photos as the scene or situation progresses if your
- department policy allows (always follow your department’s procedure for photography at scene!)
- Take photos if things must be moved and investigators are not yet on scene.
- Leave all bodies and body parts as found if possible. If bodies need to be moved to gain access to live patients, make a mental note as to the location and relay that information to the investigating officer, and included in your witness statement and fire report.
- Cordon off the affected area and limit access (when it is safe to do so).
- Do their best to preserve the integrity of evidence. Physical evidence can be very fragile; objects can be easily broken, misplaced, removed, cleaned up, destroyed and distorted.
- Preserve the scene until it has been photographed and recorded. Do not spread sand or hose down the road until after the scene is examined.
Bruising on the patient’s shoulder closest to the door side is an indication of seatbelt use. Depending on the severity of the collision forces, a deformed steering wheel may indicate that the driver was not wearing a belt. Note that if the seatbelt pretensioners were activated during the collision, the belt will not recoil. Burst threads or fibres on the belt indicate it was under load and possibly stretched. Even the floor-mounting plates that attach the lower belt sections to the vehicle could be deformed from severe force during the collision. Other signs of seatbelt use or non-use can be verified if there has been occupant impact within the vehicle; for example, hair stuck in the plastic trim on an upper A/B pillar or dash area may suggest a person was not wearing a seatbelt during a roll-over.
If rescuers use their tools in any of these areas in order to extricate a patient the metal could be distorted and evidence destroyed. If possible, the investigator should be made aware of any observed evidence. A good rule of thumb for an extrication officer is to designate dedicated debris piles of dismantled vehicle parts for each vehicle involved, facing upward to preserve crucial evidence.
Rescuers may often decide to move a vehicle from its original position to reduce extrication time or to gain access to critical patients. The officer in charge should make this decision. After a vehicle is moved, mark the former positions of the wheels on the ground if possible.
Tire-pressure monitoring systems – Federal Motor Vehicle Safety Standard (FMVSS) No. 138 – are mandatory on all new cars sold in the United States and while they are not required in Canada, most late-model vehicles have them. If a rescuer lets the air out of the vehicle’s tires, let the investigator know this was done intentionally for rescuer/patient safety and not as a result of the incident. Depending on the vehicle manufacturer, tire-pressure monitoring in late models will help determine tire inflation or blowout, which is recorded in the vehicle’s event data recorder (EDR) – also referred to as the black box.
An EDR is a device that records technical information about the occupants and the actual vehicle for a brief period of time prior, during and after a crash, typically for a few seconds. Crash data is hard written in an EDR, meaning once it is recorded it can’t be erased, even if the battery is disconnected after the crash. However, rescuers with hydraulic tools can inadvertently crush the box, which can make it more difficult to access the information stored inside. Rescuers must do their best to avoid damaging the EDR and protect the crucial evidence. With crash data, an accident reconstructionist can determine facts about the cause. (Watch for more on EDRs in a future column.)
After the extrication, the officer in charge should stop unwanted visitors from entering the cordoned-off areas. If extraneous people do have to enter the scene (i.e. tow-truck operators), make sure they are escorted to prevent them from inadvertently destroying any valuable evidence.
Emergency personnel have a responsibility to properly record all of the facts surrounding a crash/incident. As difficult as it may be, firefighters must do their best to emotionally detach themselves so that reports of the incident are rational and accurate interpretations of the events. Each firefighter’s conclusions must be centred on the facts and statements gathered, heard and known to be true. For example, if I’m rendering medical care to a patient, part of my initial assessment is to establish level of consciousness. If my patient smells of alcohol and shows signs of intoxication I would need to ask certain questions to establish this fact. I cannot assume that just because I smell alcohol on the person or in the vehicle that they are indeed under the influence of alcohol. I must ask the patient if he or she have been drinking alcohol and how much had been consumed in the last couple of hours. If the patient confirms that he or she consumed alcohol, only then can I state that in my report as fact rather than an assumption. I can write, “The patient admitted to drinking alcohol,” or, “Patient had slurred speech, blood shot eyes and his breath smelled of an alcohol-like odour.” Both statements are facts and not conclusions.
Traffic crashes are not accidents, but are avoidable events caused by a single variable or chain of variables. When an investigation is complete and the cause has been determined, anyone found guilty of causing the collision can be prosecuted. Investigations do not only apportion blame; from a rescuer standpoint, they can also highlight the need for improvements to road and vehicle safety to help prevent collisions. The goal of rescuers should be to assist traffic investigators in reducing traffic injuries and fatalities by addressing the factors that cause them.