From lecture notes and two published manuscripts on laminate composites with free-edge stresses and access to interactive computer program modules # 05a, 05b, 06, and 07, follow the outline below:

(1) Submit job for modules 05a and 06 "as-is" and print a copy to be marked up. Also print a copy of the top-frame of module 06. With these copies compare and confirm results of these two modules:

(a) For interior stresses how does the LELPA and FEM modules compare for the Type-I "WET" condition. What stresses are zero in the interior. Why? With a high-lighter pen mark and compare ply stresses listed in the output of results with those in figures. What is the laminate elastic Young's modules in the X and Y axis and the shear modulus and Poisson's ratio in the XY-plane.

(b) For Edge stresses at y/B=0.998 what stresses are zero? Why does the stress in the z-direction vary smoothly from the top to the midplane and the other stresses exhibit a discontinuity at ply interfaces? Discuss any other observations about stresses gradients as they vary from the interior (y/B=0) to the stress free edge (y/B=0.998).

(2) Submit job for modules 05b and 07 with properties for Alumina/PEEK previously calculated in assignment#3 at a fiber volume fraction of 52% and compare results with Glass/Ep. You will have to convert from pascals to psi (1 psi = 6.894E+03 pascals). Assume that PEEK does not absorb any moisture and the thermal expansion coefficients are approximately the same as unidirectional Glass/Ep.

(a) Why does the scale H/B have such a dramatic effect on the stresses gradients near the stress free edge, see Figure 4 on page 155 of Ref.[22]. Elastic properties used to calculate this stress gradient is given in Table 1 on page 151 of Ref.[22].

(b) Assume the approximation where all three shear moduli are equal and all three Poisson's ratios are also equal and explore how much this approximation changes stress free edge singularites.

(c) Why is the Poisson's ratio "NU12" so small in the section of the Module-07 form labeled
"**************** MATL. TYPE 2, 90 DEG. PLY ****************"

(d) Explore and report the stress gradients near the stress free edge for a fiber volume of 100% Alumina fiber.

Handouts:

• Ref.[21], ASTM STP 775, "Effects of Moisture, Residual Thermal Curing Stresses, and Mechanical Load on the Damage Development in Quasi-Isotropic Laminates"

• Ref.[22], ASTM STP 1012, "Edge Stresses in Woven Laminates at Low Temperatures"