الفهرس 
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Abstract
This research is to gain a better understanding of mechanical properties of epoxy resin composites reinforced with carbon fiber. An experimental and analytical investigation of the effect of size and fiber orientation on the strength of unnotched and open-hole laminates loaded in tension is presented. The carbon/epoxy angle-ply composite was manufactured considering different reinforcement orientation in the directions of 0º, ±30º, ±45º, ±60º and 90º, related to the loading direction. Notched specimens are with different hole sizes (3 mm, 5 mm, and 7 mm) and with constant width-to-diameter ratios (6). Unnotched specimens and open-hole specimens were tested in tensile testing until fracture of the samples. The tensile test samples were similar to those required for ASTM D-3039 which specified for unnotched specimens and ASTM D-5766 for notched specimens but with different widths 18 mm, 30 mm and 42mm. This study objective is accomplished in four stages: evaluate the effects of fiber orientation, Effect of hole notch on the specimens, hole diameter effect based on three different diameters (3 mm, 5 mm, and 7 mm), and effect of cross section area on the specimens according to widths 18 mm, 30 mm and 42mm. The theoretical data obtained from the strength failure theories are compared with the experimental results and a good agreement was found. In this research, the following has been concluded: • The strength of CFRE is strongly dependent on the reinforcement orientation. Specimens sustain greater load at 0-degree orientation and minimum load in other orientations. Also, extension is minimum in case of 0-degree orientation comparing with other samples. • In general, the maximum load required to break the specimens was found to decrease with decreasing the width of specimens from 42mm to 30 mm and 18 mm and by making a hole at the specimens. The effect of notch is decreasing the required load to break the material at any size. • The failure strength of conventional composite materials is greatly influenced by the presence of a notch or hole. The damage is dominated by the notch region and also influenced by notch size and sample width. • The experimental results for unnotched specimens with different orientations and for width of 18mm, 30mm and 42mm clearly identify a size effect: a decrease in width from 42mm to 30mm results in a reduction in the load of 20% for 0ᴼ direction specimens. A decrease in width from 42mm to 30mm for 30ᴼ direction specimens results in a reduction in the load of 23%. For 45ᴼ direction specimens a decrease in width from 42mm to 30mm results in a reduction in the load of 31% while 60ᴼ direction specimens had a reduction of 23% and 90ᴼ direction specimens was 17%. When the size drops from 30mm to 18 mm, the following reduction in the load was observed: 30%, 54%, 55%, 49%, and 28% for 0ᴼ, 30ᴼ, 45ᴼ, 60ᴼ, and 90ᴼ direction respectively.