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Technical Paper

Development of a Methodology for Analysis of Full Field Strains in Thermoplastic Exterior Body Panels Using Photoelastic Techniques

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.
Technical Paper

Evaluation of Liquid Applied Dampers: Impact of Polymer-Inorganic Interface on Performance

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.
Technical Paper

Instant Set Polymer-A New Dimension in Plastics

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.
Technical Paper

PVC Covered Low Density RRIM Interior Automotive Trim Components and Their Recyclability

Lightweight reinforced RIM polyurethane substrates are increasingly being specified for fully covered automotive applications such as interior door panels, instrument panels, and package shelves. In addition to offering a 30-40 % weight reduction over conventionally used substrate materials, consolidation in manufacturing steps are achieved by molding direct to polyvinylchloride (PVC), polyurethane (PU) and/or textile coverings. Weight reduction and consolidation of manufacturing steps lead to considerable part cost savings. Styling trends toward complex, deep drawn door panels, integrated with instrument panel modules, are easily fulfilled with low pressure RIM. Existing RIM capital used to produce RRIM fascia, cladding, and body panels is suitable to manufacture low density RRIM substrates (LD-RRIM).
Technical Paper

Polymeric Reflective Materials: The Future of Body Ornamentation and Lighting

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.
Technical Paper

Processing Improvements in Low Density RIM Composites

The advantage of internal mold release in the production of automotive parts such as exterior fascia and body panels is well known. Recently a new type of internal mold release technology has emerged in the area of low density RIM for interior door panels. Products have been developed for both low density reinforced RIM and structural RIM applications without sacrificing physical properties. This latest technology has the potential for producing hundreds of parts after a single application of external mold release. The exact number of parts that can be obtained will vary depending on several factors including the initial condition and design of the mold. Although able to release from aluminum or steel, adhesion to vinyl cover stock is not greatly affected. Therefore, these products can be used for both pour behind vinyl and substrate only applications.
Technical Paper

Structural Composites from RIM Mat 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.
Technical Paper

Thermal Spray Preforms: An Economical Route to SRIM Composites

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.