![]() such energy absorbers are too stiff during cold and freezing days, and too soft during hot and summer days. Moreover energy absorbers made of EPP foam show a highly variable energy absorption over the applicable temperature range, i.e. Beyond 60-70 percent compression, foams become incompressible, requiring 30-40% in-efficient construction space. ![]() This technology is time-consuming since foaming requires prolonged times in the mold due to the slow release of gases. Blowing agents used in industry are butane, dichlorodifluoromethane and carbon dioxide. Expanded polypropylene foam beads (EPP) are produced by impregnating polypropylene pellets with a volatile blowing agent in aqueous suspension under super atmospheric pressure and then reducing the pressure, whereupon the impregnated beads foam. It provides an initial level of energy absorption for low-speed impact, including reducing damage, and also provides a supplemental level of energy absorption during high-speed impact with a pedestrian.Ĭonventional energy absorbers used in automotive bumper assemblies are made from expanded polypropylene (EPP) foam or thermoplastic polymer compositions and have a large variety of shapes. The energy absorber is positioned on the front surface of the bumper beam to improve energy absorption of the bumper assembly in a pedestrian collision and also in a parking accident. With the aim of meeting various government test standards, particularly in Europe with the European Enhanced Vehicle-Safety Committee (EEVC) and in Japan, many improvements to bumpers are designed so that the bumper assembly provides a sufficient level of pedestrian injury mitigation and protects pedestrians' legs when struck by an automobile at a speed of 40 km/h.Īutomotive bumpers typically comprise several components, separately manufactured and then assembled, which include a stiff reinforcing beam, a soft energy absorber, a lower bumper stiffener and a fascia surrounding the energy absorber and having primarily aesthetic and aerodynamic functions. In addition, bumper systems are government-regulated and must meet legislated. BACKGROUND OF THE INVENTIONīumpers are used on vehicles to absorb shock and impact from collisions and to thereby prevent or minimize injury to passengers and to curtail damage to the vehicle. The present invention relates to the field of automotive bumper assemblies for pedestrian safety, particularly to the field of energy absorbers. A method of reducing collision energy transmitted to a pedestrian comprising the step of: attaching the energy absorber of claim 1 to a vehicle selected from the group consisting of a motorized vehicle, an automobile and a truck. A vehicle having the bumper assembly of claim 11, wherein the vehicle is selected from the group consisting of a motorized vehicle, an automobile and a truck.ġ3. A bumper assembly comprising the energy absorber of claim 1, a reinforcing beam and a fascia, the energy absorber being interposed between the reinforcing beam and the fascia.ġ2. The energy absorber of claim 9 made by extrusion.ġ1. The energy absorber of any preceding claim, made by injection molding, blow molding or extrusion.ġ0. The energy absorber of any preceding claim, wherein the thermoplastic material is polybutylene terephthalate (PBT).ĩ. The energy absorber of any preceding claim, wherein the thermoplastic material is made of a polyester or thermoplastic elastomers defined in ISO 18064:2003(E).Ĩ. The energy absorber of any preceding claim, wherein the thickness is variable and is between at or about 2 mm and at or about 6 mm.ħ. The energy absorber of any preceding claim, wherein the rear wall (b) has a thickness (t-b) between 0.03 w and 0.05 w.Ħ. The energy absorber of any preceding claim, further comprising a rear wall (b) that circumferentially closes the energy absorber.ĥ. The energy absorber of any preceding, further comprising a rear wall (b) that circumferentially closes the energy absorber.Ĥ. ![]() The energy absorber of claim 1, wherein the thickness of the top wall (t-c) and the thickness of the bottom wall (t-d) are equal.ģ. (measured according ISO 527-1/-2) b) yield strength between 30 and 40 MPa (measured according ISO 527-1/-2) c) modulus of elasticity between 1000-1500 MPa (measured according ISO 527-1/-2) and d) hardness Shore D between 50 ShD and 80 ShD (measured according ISO 868).Ģ. An energy absorber having a width w, a height h, a front wall a, a top wall c and a bottom wall d wherein: 1) the height h is between 0.8 w and 1.0 w 2) a thickness of the front wall (t-a) is between 0.06 w and 0.09 w 3) a thickness of the top wall (t-c) is between 0.03 w and 0.09 w 4) a thickness of the bottom wall (t-d) is between 0.03 w an 0.09 w and 5) the energy absorber is made substantially of a thermoplastic material having the following: a) elongation at break higher than 20% between −20° C. ![]()
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