G. Savage/ Engineering Failure Analysis 17 (2010)92-115 great as Table 1 implies because the fibres are extremely anisotropic, which must be accounted for in any design calculation In addition specific modulus(Elp)and strength(a/p)are only capable of specifying the performance under certain loading regimes. Specific strength and modulus are useful when considering materials for components under tensile loading such as, for example, wing support pillars( Fig. 9). The lightest component that will carry a tensile load without exceeding a predetermined deflection is defined by the high- est value of E/p A compression member such pension push rod on the other hand is limited by buckling such that the best material is that which exhibits the highest value of E//p( fig. 10) Similarly, a panel loaded in bending such as a rear wing(Fig. 11), will produce minimum deflection by optimising E lp. Nevertheless, weight savings of between 30% and 50% are readily achieved over equivalent metal components Designers of weight sensitive structures such as aircraft and racing cars require materials which combine good mechan- ical properties with low weight. Aircraft originally employed wood and fabric in their construction, but since the late 1930s aluminium alloys have been the dominant materials. during the last two decades guide the su te materials have been increas- ingly employed for stressed members in aircraft Composite structures are design ave a precisely defined quantity of fibres in the correct location and orientation with a minimum of polymer to provi upport. The composites industry achieves this precision using"prepreg"as an intermediate product(Fig. 12). 9aA Fig 9. Front wing pillars, loaded in tension. Fig. 10. Rear push rod-compression membergreat as Table 1 implies because the fibres are extremely anisotropic, which must be accounted for in any design calculations. In addition specific modulus (E/q) and strength (r/q) are only capable of specifying the performance under certain loading regimes. Specific strength and modulus are useful when considering materials for components under tensile loading such as, for example, wing support pillars (Fig. 9). The lightest component that will carry a tensile load without exceeding a predetermined deflection is defined by the high￾est value of E/q. A compression member such as a suspension push rod on the other hand is limited by buckling such that the best material is that which exhibits the highest value of E1/2/q (Fig. 10). Similarly, a panel loaded in bending such as a rear wing (Fig. 11), will produce minimum deflection by optimising E1/3/q. Nevertheless, weight savings of between 30% and 50% are readily achieved over equivalent metal components. Designers of weight sensitive structures such as aircraft and racing cars require materials which combine good mechan￾ical properties with low weight. Aircraft originally employed wood and fabric in their construction, but since the late 1930s aluminium alloys have been the dominant materials. During the last two decades composite materials have been increas￾ingly employed for stressed members in aircraft. Composite structures are designed to have a precisely defined quantity of fibres in the correct location and orientation with a minimum of polymer to provide the support. The composites industry achieves this precision using ‘‘prepreg” as an intermediate product (Fig. 12). Fig. 9. Front wing pillars, loaded in tension. Fig. 10. Rear push rod – compression member. G. Savage / Engineering Failure Analysis 17 (2010) 92–115 97