Search Results

Damping materials are applied to the vehicle body during production to provide passenger comfort by reducing noise and structural vibration through energy dissipation. Noise, Vibration, and Harshness (NVH) Engineers identify critical areas of the vehicle body for material placement. Damping materials, which include liquid applied dampers, are typically applied directly on the structure, covering large areas. These film forming materials can be spray applied using automation and, after baking, result in a cured viscoelastic damping layer on the target substrate. Typical liquid applied dampers contain an aqueous dispersion of film forming polymer which functions to bind inorganic materials together in the coating and provide a composite structure that dissipates energy. Representative damping coatings were prepared from dispersions of polymers with varying viscoelastic properties and chemical compositions.

Over the past decade damping materials have contributed major improvements to passenger comfort. Noise Vibration and Harshness (NVH) engineers have further shaped material specifications to reflect key targeted properties that improve vehicle design. The specified damping material is then applied to the formed surfaces of the vehicle body to provide optimal performance and achieve the required results. This paper describes how liquid dampers have advanced to meet increased performance requirements through improved loss modulus of the final coating. Data generated by dynamic mechanical analysis shows that this viscoelastic behavior is what drives the performance in damping materials. Through the correlation of loss moduli to damping performance of Oberst bars, the mechanism can be further quantified and explained.

Before the 1970s, plastics were considered primarily as non-engineering materials and were used in applications such as belts, hoses, gaskets, carpet backing, sealing, adhesives, tires, and so forth as a part of an engineering solution. More recently, plastics have replaced traditional materials and emerged as a significant "engineering application" within the automotive industry. Plastics have proven to be cost effective while providing automakers with the design freedom to accommodate safety, styling, and comfort. Engineering Plastics and Plastic Composites In Automotive Applications focuses on some of the various types of plastics and plastic composites and their applications and advantages within passenger vehicles.

The blow molded knee bolsters on the 1996 Chevrolet Astro and GMC Safari vans are the first blow molded parts used on an interior structural application. These knee bolsters also meet FMVSS 208 requirements. The one-piece bolsters, used on both the driver's and passenger's sides of the vehicle reduced cost by $4.00 and weight by 40% per vehicle compared with two-piece, steel-reinforced plastic knee bolsters. Additional savings were realized in tooling cost reductions of $300,000 and a development time that was shortened by 64 weeks. Part testing was also reduced to the tunability of the process. Aesthetic concerns of matching adjacent injection molded and vinyl parts were also met. This paper discusses the combination of material, processing and tooling technologies that made this program a success.

Revisions to the FMVSS 201 head impact legislation have had a significant impact on the design and engineering of upper interior trim components of cars and light trucks. Structural performance with energy absorbing capability to prevent head injury is now a significant addition to these requirements. However, occupant visibility blockage limits the amount of packaging space available for implementing countermeasures in this area. A novel approach to meeting the FMVSS 201 structural requirements, while keeping the interior trim on the vehicle minimally changed, has been developed. This approach requires the use of energy absorbing rib structures sandwiched between the trim panel and the inner body-in-white (B/W) sheet metal in A and B pillars. Heat staking is used to attach the rib structure to the interior trim panel.

The use of color concentrates for coloring unpainted automotive interior trim components made from low gloss ABS resins is a well established practice. Several grades of ABS are used to match the heat and light stability requirements for particular part locations within the vehicle, and each resin requires a different color concentrate formulated specifically for the resin. A potential cost savings exists if some of these color concentrates can be consolidated and still produce parts which meet the color requirements of the automotive industry. This paper discusses the development efforts required to implement such a concept and the benefits that result. The successful coloring of two grades of ABS with one color concentrate indicates that the resin pair is co-colorable.

An innovative and economical new method has been developed to fabricate glass fiber preforms in the Structural Reaction Injection Molding (SRIM) process to produce structural composite components. The method involves blowing a resin powder through a ring of flame in a commercial thermal spray gun to achieve a melt, and directing the melt onto a fiber reinforcement where the polymer solidifies on contact and binds the fibers together. The fibers are fed through a chopper gun and cocurrently deposited with the binder onto a screen in the shape of the part. A vacuum is applied to the back of the screen by a blower to hold the fibers in place. The thermal spray process has significant economical advantages over the use of mat to fabricate preforms due to lower raw material costs and waste. It also has many advantages over traditional directed fiber processes, including capital and energy savings from the elimination of the preform drying operation.

A new family of homogeneous polyolefin copolymers can be produced by Dow's INSITE* Technology. These ethylene/octene based, designated as polyolefin plastomers (POP) and polyolefin elastomers (POE), exhibit many unique physical and mechanical properties1,2,3,4 due to their narrow composition distribution (i.e., comonomer distribution and molecular weight distribution). In addition, the INSITE* technology also allows for the production of homogeneous copolymers with a controlled level of long chain branching (LCB) along the polymer backbone. This unique molecular structure results in many improved rheological properties5, such as enhanced shear thinning and high melt elasticity, and improved polymer melt processability6. Additionally, the unique rheological properties of the INSITE Technology polymer (ITP) also provide improved dispersion capability in rubber modified polypropylene (PP) blends.

Polymeric Reflective Materials (PRM) offer the automotive designer a unique new material and processing technology for vehicle ornamentation and lighting. PRM is a highly reflective multi-layer thermoplastic extruded sheet containing no metallization or surface coatings to create it's reflective appearance. PRM's ability to “transflect” light is a very unique characteristic. Transflection is the ability to simultaneously transmit and reflect light. PRM enables the integration of lighting components and exterior ornamentation to create uninterrupted exterior styling lines. PRM allows lighting components to disappear. Targeted applications include rear lighting lenses, illuminated body trim, emblems, door edge guards, safety lights, etc. Additionally, unique visual effects are created by front and second surface decorating. PRM also offers many interior styling options.

Thermoplastics are rapidly gaining acceptance throughout the automotive industry as an attractive alternative to steel for exterior automotive body panel applications. The transition from steel to thermoplastic is driven primarily by the unique balance of physical properties derived from this new class of engineering polymers. These properties include corrosion resistance, dent resistance and reduced production costs. However, it is recognized that thermoplastic parts must be designed such that the stresses imposed on the component in service are minimized. By minimizing the strain and corresponding stress, the designer could help prevent problems associated with cracking induced by solvents or constraint at the panel attachment locations. This paper proposes a new methodology for analysis of full field stresses in thermoplastic exterior body panels. The methodology utilizes photoelastic stress analysis techniques to define areas of maximum stress in injection molded components.

The manufacture of plastic components typically involves large deformations of the material, interaction with rigid boundaries, and a material constitutive response which depends strongly on temperature and the rate of straining. In service, material response may change with time, and a component may undergo large deformations under load. Numerical analysis of manufacturing processes and of plastic components under load must account for these nonlinear effects. The paper discusses nonlinear finite element analysis in the context of plastics manufacturing and in-service loading of plastic components. Some currently available techniques are illustrated with an example of creep induced buckling, an example of warping due to post-forming cooling, and a case involving blow molding.

The commercial success of reaction injection molding (RIM) has led to concepts using RIM machinery to mold high modulus glass reinforced composites. This paper describes the static and dynamic mechanical properties of three different resin systems based on polyisocyanurate and polycarbamate chemistries with the use of a continuous glass mat.

A new plastic and processing technology known as ISP (Instant Set Polymer) has been developed that allows production of essentially any size part via liquid injection molding. Mold cycle (60 sec) is independent of part area or thickness (1/4″ to 6″). Items 12 inches thick and weighing 200 lbs have been successfully produced.

The Dow system for obtaining a gasoline barrier in high density polyethylene fuel tanks reduces permeation by roughly 95%, is permanently adhered to the surface, does not affect the physical properties of the high density polyethylene, survives normal flexure intact, and can be applied to the tank during its fabrication at a relatively low cost.