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Some results are descibed of an innovative approach for producing net shape polymer, ceramic and carbon composites using wood and other lignocellulose precursors. Wood monoliths have been carbonized without producing cracks as typically found in charcoal materials. These porous carbon monoliths have been readily shaped using standard tools. Conversion to final material has been accomplished without any change in dimensions from the carbon stage, The net-shape materials produced include carbon/epoxy and carbon/carbon composites, silicon carbide, silicon carbide/silicon composites, titanium carbide, and aluminum nitride. Carbonized poplar has been found to be 30% stronger and a carbon/epoxy derived from poplar 250% stronger than the original poplar wood.

This research demonstrated for the first time a method for producing net shape polymer, ceramic and carbon composites using wood as a precursor. The conversion of wood to carbon has been practiced for centuries but the controlled thermal decomposition to form a monolithic carbon to be used as a template for composites as demonstrated by this research is a unique discovery. This was accomplished by thermal decomposition of wood under controlled conditions to produce a crack-free porous carbon monolith which was readily shaped by conventional methods. The shaped carbons have converted to carbon/polymer composites, carbon/carbon composites, ceramics, and ceramic composites without significant changes in dimensions. This research has demonstrated that composites derived from wood can eliminate several expensive processing steps. Specifically, no fiber lay-up or powder consolidation is required, and final grinding and polishing steps are minimized.

A unique process for conversion of monolithic wood structures to carbons that retain the cellular structure of the wood without the formation of cracks and other defects associated with charcoal materials is described. A variety of wood species are carbonized to produce the materials which are characterized using TGA, density, dimensional changes, acoustic velocity, SEM and mechanical testing. We demonstrate that through controlled pyrolysis monolithic carbonized wood can be produced without the macro-cracks normally associated with charcoal. A linear relationship is established between the bulk densities of wood and carbonized wood which spans the entire range of species. For the conditions presented, the carbonized wood had 82% of the bulk density of the precursor wood. Carbonized wood acoustic velocity ranged from 4.7 to 1.3 mm/μs for Tilia americana and Ochroma pyramidale , respectively. Carbonization resulted in decreased acoustic velocity in the axial principal direction and increases in the radial and tangential directions. Acoustic anisotropy was retained through carbonization, but reduced in magnitude. Mechanical testing showed the carbonized wood to be 28% stronger than the precursor. The cellular morphology of the porous carbonized wood is described and compared to carbon foams.

There has recently been considerable interest in the behavior of thick section (one inch and greater) polymer composites under compressive loads [1]. Strength, fatigue life and damage modes are characteristics which design and inspection engineers seek to understand to properly utilize these materials in applications where compressive loads are encountered. This paper presents a brief summary of some of the progress in a research effort to characterize the compression-compression fatigue behavior of thick section fiber reinforced polymer composites. Primary objectives of this research are to determine fatigue life and strength, and to use nondestructive techniques to predict material failure with particular interest in identifying the early stages of damage. Destructive techniques are implemented to correlate actual damage mechanisms to any “fingerprint” found by NDE methods. Specifically, one inch thick, double edge notched, graphite epoxy coupons were fatigued to failure while structural stiffness and acoustic emissions were monitored. Unfailed specimens were examined using ultrasonic C-scan and X-ray radiography after which they were cut and polished for damage identification via microscopy.