Search Results

The rigid-rigid polymer toughening concept, i.e., utilization of an engineering polymer to toughen another engineering polymer, was employed to improve the fracture toughness of isotactic polypropylene (iPP) and to maintain the rigidity and heat deflection temperature of iPP. Noryl Poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) is chosen as the toughener phase to toughen PP. The fracture toughness of PP can be significantly improved by adding rigid thermoplastics PPO without causing any reduction in modulus. Incorporation of a small amount of styrene-ethylene-propylene (SEP) rubber compatibilizer, which helps reduce the size of PPO particles from 15 μm down to about 0.5 μm, further improves the toughness of iPP/PPO blends. Detailed fracture mechanism investigation reveals that Noryl PPO particles help trigger massive crazing in the PP matrix and serve to stabilize the growing crazes.

One of the methods used to mechanically fasten a component such as a radio, cluster or finish panel to a plastic instrument panel substrate involves driving a screw through a metal push-nut which has been inserted into an opening in the plastic instrument panel substrate. A primary failure mode which has been observed for this type of joint is cracking of the plastic substrate surrounding the metal push-nut. Finite Element Analysis (FEA) has been employed to optimize the design of the push-nut opening in a polycarbonate substrate and minimize the potential for cracking of the plastic. For the FEA, the implicit version of the ABAQUS program was used. It was determined that the induced stress in the plastic instrument panel substrate from the fastening process can be minimized by controlling the dimensions of the push-nut opening such that push-nut recess is minimized and the thickness of the substrate in the region whether the push-nut engages is optimized.

Pigmented & mineral-filled PP (PF-PP) is marketed as a potential alternative to ABS for automotive interior applications. However, PF-PP is easily damaged by scratching its surface, thus limiting its acceptance for interior applications. This study investigates the test methods to quantify the extent of scratch & mar damage, and the effect of different mineral fillers towards improving the scratch & mar resistance of PF-PP.

An experiment was conducted to measure the surface pressures and sectional side forces on a 5° cone with three nose tips. The nose tips included a sharp, an 8.7% blunt, and a 17.5% blunt nose tip. Rings of pressure orifices were located at 40% and 80% of the model length and the model was rolled from ±180° in 9° increments to determine roll dependence. The sectional side force data for the sharp cone showed a strong dependence on the roll orientation of the model. The blunt nose cone configurations also showed a dependence on roll orientation. The blunt nose configurations were effective in reducing the sectional side force for angles of attack up to 25°. However, at angles of attack greater than 35°, the reduction was no longer significant. Pressure distributions for three angles of attack are presented to highlight details of the flow when: vortex asymmetries are just beginning; the vortices are in a steady asymmetric state; a vortex has shed between the 40% and 80% stations.