The application of fiber-reinforced polymer (FRP) composites as piling materials in harsh environments has gained popularity due to their high corrosion resistance. FRP composites can be fabricated using different types of epoxy resin matrices and fibers. This study aims to investigate the interface behavior between sand and FRP materials with varying levels of hardness, with a particular emphasis on the abrasive surface wear of FRP. Monotonic interface shear tests (under normal stresses of 50, 100, 200, and 400 kPa) and interface shear tests repeated 20 times (under normal stresses of 200 and 400 kPa) are performed. The local surface roughness of the FRP plates is measured for tested samples under both monotonic and repeated loadings using laser scanning to evaluate the accumulated abrasion effect. The results of monotonic tests indicate that under a given shear displacement and normal stress, the samples with softer FRP plates exhibit higher interface friction angles and more pronounced dilative behavior. Following repeated tests, the interface friction angles of softer FRP specimens decrease, while the surface roughness of the FRP plates gradually increases. However, for the softest FRP plate, its surface is severely damaged after repeated tests under high normal stress levels, leading to unstable changes in the test results.

External contamination (soiling) of the incident surface is a major limiting factor for solar technologies. A 5year field glass coupon study was conducted to better understand external contamination and its effects; compare cleaning methods and the use of preventative coatings; and explore the abrasion resulting from cleaning to advise on accelerated abrasion testing. Test sites included the cities of Dubai (UAE), Kuwait City (Kuwait), Mesa (AZ), Mumbai (India), and Sacramento (CA). Through the 5-year cumulative study, dry brush, water spray, and wet sponge and squeegee cleaning methods were compared to no cleaning. Optical microscopy was used to obtain images, including representative color images, grayscale images for object analysis, and oblique images for coating integrity assessment. A thresholding protocol was developed to analyze and distinguish specimens using the ImageJ software. Optical performance was quantified using a spectrophotometer, including comprehensive optical characterization (transmittance, reflectance, and absorptance in addition to forward- and back- scattering). Atomic force microscopy was used to verify the abrasion damage morphology, including the width and depth of surface scratches. Analysis of the results included correlation of optical performance and particle area coverage, rank order (by coating or location), and the acceleration factor for abrasion damage. The efficacy of external cleaning was more readily distinguished from the effectiveness of antisoiling coatings. The acceleration factor for dry brush cleaning of a porous silica coating was found to be on the order of unity.