Low and high velocity impact response of thick hybrid composites

The effects of low and high velocity impact on thick hybrid composites (THC's) were experimentally compared. Test Beams consisted of CFRP skins which were bonded onto an interleaved syntactic foam core and cured at 177 C (350 F). The impactor tip for both cases was a 16 mm (0.625 inch) steel hemisphere. In spite of the order of magnitude difference in velocity ranges and impactor weights, similar relationships between impact energy, damage size, and residual strength were found. The dependence of the skin compressive strength on damage size agree well with analytical open hole models for composite laminates and may enable the prediction of ultimate performance for the damaged composite, based on visual inspection

Method and apparatus for measuring the strain developed in a coated surface

A method and apparatus are provided for determining the strain developed in a coated surface. A beam with a coating on a surface thereof is mounted as a cantilever and a force is applied to the free end of the beam to cause deflection of the beam until the coating on the beam fails. The strain in the beam, and hence in the coating at the point of failure, is determined based on the dimensions of the beam, the point along the beam where failure of the coating occurs and the amount of deflection of the beam, and this determination is made independently of the temperature of the beam and the material from which the beam is made. The determination is made based on the equation E= 1.5hdx/l(exp 3), where E is strain, h is the beam thickness, d is the beam deflection, x is the distance from the free end of the beam to the point where failure of the coating occurred, and l is the length of the beam

Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates

Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams

Durable Advanced Flexible Reusable Surface Insulation

An improved flexible blanket includes a nickel-based alloy foil layer brazed to a nickel-based alloy fabric layer. The fabric layer is stitched to an underlying ceramic insulation layer

Characterization and modeling of nonlinear viscoelastic response of PEEK resin and PEEK composites

The viscoelastic properties of PEEK resin and unidirectional PEEK composite APC-2 were characterized by an accelerated testing procedure based on the time-temperature and time-stress superposition principles. The results obtained by creep and recovery tests are presented, and the constitutive modeling of the nonlinear viscoelastic response is discussed. The stress-dependent viscoelastic responses of the composite were modeled by a special case of Schapery's nonlinear viscoelastic equation with a kernel of the general power law. The relations for the temperature-time scale shift factors and stress-time scale factors are given. With the equations and parameters presented, the linear and nonlinear viscoelastic behaviors of APC-2 composite laminate from ambient temperature up to the glass transition temperature can be described analytically. Comparisons were made on the nonlinear properties of the 15° off-axis laminate, transverse laminate and pure resin. The results agree with the theory that the matrix octahedral shear stress is the main variable determining the nonlinearity of polymers and polymer-based composites. © 1994.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Familial Recurrence Patterns in Congenitally Corrected Transposition of the Great Arteries: An International Study

International audienc