ABSIXACT: This paper describes an experimental study on the tensile creep behavior of a random continuous fiber mat reinforced polypropylene composite, commercially known as Azdel. A special experimental setup was designed and used to conduct these creep tests at 75 and 100°C with stress levels ranging from 30 to 60 percent of the tensile strength of Azdel. The test duration was 3,000 hours or the time to creep rupture response, whichever occurred first. A straight line on a semi-log plot adequately described the relationship between the imposed stress and the creep rupture response time for the range of stress levels studied. Moreover, the estimated secondary creep mte was inversely related to the observed creep rupture response time. INTRODUCI'IONELEcriNG COMPOSITE MATERIALS for long term applications at elevated S temperatures requires knowledge of their creep behavior. In creep tests, a constant stress is applied on the specimen and the strain is measured as a function of time. The increase in strain with time is known as creep. Depending on the stress level and ambient temperature, the specimen can also fail, thereby terminating the creep test. This fidure phenomenon is known as creep rupture and occurs at stresses much lower than the static tensile strength of the material.Creep behavior of composite materials has been studied only to a limited extent, mainly due to the fact that continuous fiber composites in thermosetting matrices do not exhibit large creep strains at their use temperature 111. However, creep deformation may be relatively large if the fiber orientation is random and/or the matrix is a thermoplastic resin. There are a few reported studies on the creep characteristics of random fiber sheet molding compound (SMC-R) composites [2-3]. In these studies, the matrix was a thermosetting resin, such as Journal of COMPOSITE MATERIALS,

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For many years, use of 30:70 solder (30 percent tin, 70 percent lead) was common in diesel truck radiators. The 30:70 alloy was relatively brittle, however, and became prone to stress cracking, a result of vibrational stresses built up in the radiators. This led to failure of soldered joints, causing leaks and eventual failure of the engine. At engine manufacturers' requests, solder producers worked to develop a better solder alloy. Eventually a soft solder alloy was produced which could better withstand engine vibrations. This soft solder, sometimes called silver solder, has the following approximate composition: 97 percent lead, 1.5 to 2.5 percent tin, and 0.5 percent silver. Dearborn Chemical (U.S.) has had a long-term treatment development program for closed cooling systems, resulting in an inhibitor which has given excellent performance in the field. This inhibitor also performs well when screened by ASTM Corrosion Test for Engine Coolants in Glassware (D 1384-70). Shortly after engine manufacturers began to use the new soft solder alloy, reports of severe solder corrosion came in from the field. Laboratory tests were then done using soft solder. Initial data developed by ASTM D 1384 showed that tests using soft solder specimens gave only slightly higher solder corrosion rates than tests using 30:70 solder in inhibited standard corrosive water. Further testing, however, did not reproduce data similar to the first set of data obtained using soft solder. Because reproducibility of screening test results using soft solder was poor, a study was undertaken to examine variability of soft solder corrosion results. Tests performed were based on ASTM D 1384. Data developed lead to two basic conclusions. First, corrosion rates for soft solder tend to be higher than those for 30:70 solder and corrosion rates of soft solder deviate much more from a mean value (for a given inhibitor dosage) than for 30:70 solder. This holds for water coolants and water-ethylene glycol coolants, both inhibited or uninhibited. Second, the water-ethylene glycol coolant is much more aggressive to both solder alloys than is standard corrosive water. This is the case for inhibited and uninhibited solutions.