JEC COMPOSITES MAGAZINE - Issue #35 - September 2007 - 66

KNOW-HOW Testing g…/… Non-destructive evaluation Intercalated montmorillonite nanocomposites were shown to reduce micro-cracking and improve the mechanical characteristics of carbon/cyanate laminates through better stress distribution and thermal cycle structural relaxation. We expect similar effects to take place in the carbon/PEEK and, particularly, somewhat less robust carbon/PPS prepregs. One of the tested compositions is based on the material prepared from the organoclay Nanocor® 1.34TCN, a maleic anhydride grafted polypropylene Epolene®G-3003 and regular polypropylene, by reacting a three-component suspension in xylene. The resulting powder in an optimized ratio of PP/EpolenClay 85:10:5 was then extruded to ensure uniform thermal stability for all the materials and used as an additive component in 1-5% quantity. More information Neo-Advent Technologies (NAT) is a new product development company founded in 2004 with a focus in polymers, adhesives, and coating products. Company has about 1000-sq./ft. of combined shop, laboratory, and office space in Marlborough, Massachusetts. It has a fully equipped tool shop for the manufacture of mechanical components. radial direction was: E1=1.74*10 N/m and the modulus of elasticity in the tangential direction was: E2=1.45*10 N/m . 10 2 Testing mechanical and thermal properties of the prepreg laminates We will test the key mechanical properties of the laminated plates (25x2.4 mm) in different lengths including tensile and compression strength (modulus) at 0, ±45° and 90° configurations, shear strength/modulus, and inter-laminar shear strength. The thermal properties of interest – thermal expansion coefficient (CTE) and thermal conductivity – will be examined. The combined test panel will be based on the following ASTM standards: ASTM D638 “Test Method for Tensile Properties of Polymer Matrix Composite Materials”, ASTM D696 “Test Method for Compression Properties of Polymer Matrix Composite Materials”, ASTM D732 “Shear Strength of Plastics by Punch Tool”, ASTM D903 “Peel or Stripping Strength of Adhesive Bonds” and ASTM D696 “Coefficient of Linear Thermal Expansion of Plastics”. We will also examine the microscopy of the laminate surface after thermal cycling for the presence of microcracking. The thermal stresses in the nose cap manufactured from graphite epoxy or carbon-carbon composites can reach a significant value. However, these stresses can never reach the failure threshold. For the experimental data, we selected a satellite lattice structure model with the following geometrical dimensions: Ro=10”(.254m); Ri=9”(.228m); r=9.5”(.241m). This model was fabricated from graphite epoxy and the density of the material was: ρ=.420*10 kg/m . The Poisson ratio was: µ12=µ21 =.036. 3 3 The Poisson ratio was: α12=·α21 =.036, while the coefficient of ther-mal conductivity for carbon/carbon was α=-.903*10 m/hrm /°C. -14 2 The correlation between the radial (α11) and tangential (α22) thermal stresses and the temperature gradient T was determined. For carbon/carbon composites, the coefficient of thermal expansion in the radial direction is: ·α1=-5.45*10 m/m/°C and in the tangential direction: α2=-5.34*10 m/m/°C. The coefficient of thermal expansion in an arbitrary direction was determined as α12=2sinα·*cosα (α1-α2). The significance of the carbon/carbon thermal stress components for the satellite model changed when the gradient of temperature changed from -14°C to -17°C in the compression zone. The same is true for the tension zone. Future developments in NDE methods will include determining the thermal stresses and strength parameters. -6 -6 Concluding remarks A methodology was established for predicting the strength and stiffness of advanced carbon/boron fibres and liquid polymer composites that are manufactured using the vapour deposition nanoscale technology, and for the non-destructive evaluation of space satellite components by ultrasound, X-ray, digital radiography and thermography technologies.The holography optical interferometer technique was extended to composite lattice structures. As an example, deflection on the cantilever bar was demonstrated using a Nikon digital camera. The thermal stresses on lattice composite structures were calculated using parameters which were found by ultrasound and thermography technologies. We used NDE thermography cameras with highresolution images. The probability of local cracking can be predicted using micromechanics models by computing slices of composite layers. In spite of the visibility of cracks, the samples tested reflect 90% of the initial strength. However, it is very important to use nondestructive evaluation methods to detect non-visible cracks. Contact: yosif105@hotmail.com When the modulus of elasticity was calculated for the satellite model, the velocity of rotation changed from 3,627 rad/sec to 4,800 rad/sec and to 7,000 rad/sec. The modulus of elasticity in the radial direction was: E1=3.4*10 N/m , while the modulus of elasticity in the tangential direction was E2=2.5*10 N/m (see Table 6). The coefficient of thermal expansion in the radial direction was: · α1= -5.45*10 m/m/°C, while in the tangential direction it was: α2=-5.34*10 m/m/°C. 10 2 10 2 -6 -6 A second satellite model was fabricated from carbon/carbon and had a density of: ρ=.548*10 kg/m . The modulus of elasticity in the -3 3 JEC Composites Magazine / No35 September 2007

JEC COMPOSITES MAGAZINE - Issue #35 - September 2007

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