Relationship between Structure and Mechanical Properties of

Chapter 20

Relationship between Structure and Mechanical Properties of Polydiacetylenes R. J. Young

Downloaded by TUFTS UNIV on October 19, 2016 | http://pubs.acs.org Publication Date: March 26, 1987 | doi: 10.1021/bk-1987-0337.ch020

Department of Polymer Science and Technology, Manchester Institute of Science and Technology, University of Manchester, Manchester M60 1QD, United Kingdom

Polydiacetylenes offer a unique opportunity of studying structure/property relationships in polymers. This paper is concerned with structural factors which control mechanical properties. The effect of the size of sidegroups upon the Young's moduli of different polydiacetylenes is discussed briefly. The effect of internal and surface defects upon the strengths of individual fibres is also described. Examples are given of how Raman spectroscopy can be used to follow the deformation of fibres and it is shown how this can be extended to fibres in composites. The general mechanical properties of the composites are also described. Polydiacetylene single c r y s t a l s produced by the s o l i d - s t a t e polymeri z a t i o n of substituted diacetylene single c r y s t a l monomers (1,2) offer a unique opportunity of studying structure/property relationships i n polymers. The s o l i d - s t a t e polymerization technique enables highlyperfect polydiacetylene single c r y s t a l s to be produced as either lozenges (3) or f i b r e s (4) with macroscopic dimensions. This can be contrasted with the case of conventional polymers such as polyethylene which i s obtained as p o l y c r y s t a l l i n e s p h e r u l i t i c samples when c r y s t a l l i z e d from the melt (5) or as microscopic chain-folded lamellar single c r y s t a l s from d i l u t e solution (6). Neither of these two morphologies are p a r t i c u l a r l y useful for the study of structure/ property r e l a t i o n s h i p s . Spherulitic polymers have complex structures (5) and the lamellar single crystals can generally only be studied i n the electron microscope (6»). Many of the fundamental investigations of structure/property relationships i n metal c r y s t a l s have involved the use of large single c r y s t a l specimens (7). In the past there have been several attempts to investigate the relationship between structure and mechanical properties i n polyethylene. I t has proved possible to produce samples of the polymer with a s i n g l e - c r y s t a l texture (8) but they are s t i l l p o l y c r y s t a l l i n e and certain ambiguities remain concerning the detailed deformation mechanisms i n such samples (9). There have also been reports of studies of the deformation of single c r y s t a l s of polyethylene on extensible substrates (10,11). Because the polymer

0097-6156/87/0337-0266$06.00/0 © 1987 American Chemical Society

Sandman; Crystallographically Ordered Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1987.


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molecules are oriented perpendicular to the surface of the lamellar c r y s t a l s (5) deformation i s limited to directions perpendicular to the chain d i r e c t i o n . Also forces or stresses cannot be measured f o r the microscopic c r y s t a l s . Polymer s c i e n t i s t s were therefore frustrated for many years by the lack of polymer crystals with suitable morphologies. It was r e a l i s e d that the fundamental problem was the d i f f i c u l t y of arranging the long tangled and coiled molecules of a molten polymer or polymer solution i n a single c r y s t a l . Hence, there was considerable excitement when polymer chemists started to examine the p o s s i b i l i t y of producing polymer crystals by the solid-state polymerization of single c r y s t a l monomers (JO . Some of the f i r s t attempts, however, were rather disappointing. For example, single crystals of trioxane were found to undergo polymerization to polyoxymethylene i n the s o l i d state but the polymer produced was found to be p o l y c r y s t a l l i n e with a complex morphology (12). Such problems are not normally encountered with the topochemical polymerization (Y) of a large number of d i f f e r e n t l y substituted diacetylene d e r i v a t i v e s . This has led to the development of highly-perfect polydiacetylene single crystals with macroscopic dimensions which have enabled s i g n i f i c a n t advances to be made i n our understanding of the r e l a t i o n ship between the o p t i c a l , electronic and mechanical properties and the structure of polymer c r y s t a l s (2). This paper reviews recent work upon structure/mechanicalproperty relationships i n polydiacetylenes. I t i s shown how t h i s has led to the development of high strength polydiacetylene single c r y s t a l fibres and their performance as reinforcing f i b r e s i n composites i s described. Structure Morphology. In general, polydiacetylene single c r y s t a l s are found i n one of two c r y s t a l morphologies, either as lozenges or as f i b r e s . The morphology i s controlled by the conditions under which the monomer i s c r y s t a l l i z e d although the exact reasons why a p a r t i c u l a r morphology i s obtained are not f u l l y understood. The toluene sulphonate derivative (TSHD) (3) i s normally obtained i n the form of lozenges from most solvents whereas the carbazolyl derivative (DCHD) (4) i s usually obtained as f i b r e s , the aspect r a t i o of which depends upon the solvent, solution concentration and c r y s t a l l i z a t i o n conditions. In contrast the ethyl urethane derivative (EUHD) (13,14) can be obtained i n three c r y s t a l forms, only one of which can undergo solid-state polymerization to give fully-polymerized single c r y s t a l f i b r e s (13). An example of fibrous c r y s t a l s of this derivative i s given i n Figure l a . Electron Microscopy. X-ray d i f f r a c t i o n methods have been used to determine the c r y s t a l structures of many polydiacetylene derivatives to a high degree of accuracy and precision (15-17). This depth of knowledge of the c r y s t a l structures i s invaluable f o r the purpose of r e l a t i n g mechanical behaviour to structure. Although X-ray d i f f r a c t i o n i s the most accurate method of determining c r y s t a l structures considerable extra information can be obtained using transmission electron microscopy (18-20). Studies upon polydiacetylene single crystals have enabled the detailed structure of defects


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Figure 1 (a) Photograph of polydiacetylene single c r y s t a l fibres on mm graph paper, (b) L a t t i c e planes i n poly DCHD, spacing 1.2 nm.



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such as t w i n s ( 2 1 ) , d i s l o c a t i o n s (19,22) and s t a c k i n g f a u l t s (23) t o be e l u c i d a t e d . I t has a l s o enabled the geometry of s u r f a c e d e f e c t s such as s t e p s ( 2 4 ) , which c o n t r o l the s t r e n g t h of s i n g l e c r y s t a l f i b r e s , t o be a n a l y s e d i n d e t a i l . One problem n o r m a l l y encountered w i t h o r g a n i c m a t e r i a l s such as polymers i n the e l e c t r o n microscope i s r a d i a t i o n damage whereby the c r y s t a l s t r u c t u r e i s d e s t r o y e d by exposure t o the e l e c t r o n beam ( 1 9 ) . I t has been found t h a t most p o l y d i a c e t y l e n e s a r e r e l a t i v e l y s t a b l e and t h a t polyDCHD i s p a r t i c u l a r l y o u t s t a n d i n g i n i t s a b i l i t y t o r e s i s t damage i n the e l e c t r o n beam (19) b e i n g o v e r 20 times more r e s i s t a n t than p o l y e t h y l e n e . T h i s h i g h s t a b i l i t y has a l l o w e d d e t a i l e d s t u d i e s t o be made of the s t r u c t u r e of polyDCHD a t h i g h m a g n i f i c a t i o n . I t has been found t h a t the c r y s t a l l a t t i c e can be imaged d i r e c t l y i n the e l e c t r o n microscope (19,24) and an example of t h i s i s shown i n F i g u r e l b where p l a n e s p a r a l l e l t o the c h a i n d i r e c t i o n can be seen. As w e l l as b e i n g an i n t e r e s t i n g e x e r c i s e i n e l e c t r o n m i c r o s c o p y t h i s imaging of the c r y s t a l l a t t i c e shows the p e r f e c t alignment of the polymer m o l e c u l e s i n polyDCHD c r y s t a l s and the r e l a t i v e l y d e f e c t - f r e e n a t u r e of these m a t e r i a l s . Mechanical P r o p e r t i e s S t r e s s / s t r a i n behaviour. I n 1974, Baughman, G l e i t e r and S e n d f e l d (25) demonstrated t h a t f i b r e - l i k e c r y s t a l s of the phenyl u r e t h a n e s u b s t i t u t e d p o l y d i a c e t y l e n e , polyPUHD c o u l d be deformed e l a s t i c a l l y t o s t r a i n s of over 3%. The c r y s t a l s were found t o have h i g h v a l u e s of Young's modulus i n the c h a i n d i r e c t i o n of the o r d e r of 45GPa. The work has s i n c e been extended to o t h e r p o l y d i a c e t y l e n e s w i t h modulus v a l u e s of 45GPa b e i n g r e p o r t e d f o r polyDCHD (24) and 62GPa f o r polyEUHD ( 1 4 ) . A t y p i c a l s t r e s s / s t r a i n c u r v e f o r a polyDCHD s i n g l e c r y s t a l f i b r e i s g i v e n i n F i g u r e 2. The curve i s l i n e a r up t o a s t r a i n o f about 1.8% and t h e r e i s a s l i g h t decrease i n s l o p e above t h i s s t r a i n u n t i l f r a c t u r e o c c u r s a t a s t r a i n of about 2.8%. I t has been suggested (25) t h a t t h i s n o n - l i n e a r b e h a v i o u r , w h i c h i s n o t a y i e l d p r o c e s s , might be due t o the anharmonic p a r t of the i n t e r a c t i o n p o t e n t i a l between n e i g h b o u r i n g atoms on the polymer backbone. T h i s has been c o n f i r m e d u s i n g Resonance Raman Spectroscopy (26) where i t has been shown t h a t the f r e q u e n c i e s of a l l the m a i n - c h a i n c a r b o n carbon s t r e t c h i n g modes decrease w i t h a p p l i e d s t r a i n . The consequent r e d u c t i o n i n the f o r c e c o n s t a n t s i s one of the f a c t o r s l e a d i n g t o a r e d u c t i o n i n t h e s l o p e o f the s t r e s s / s t r a i n c u r v e a t h i g h s t r a i n s (14,24,25) Young's modulus. P o l y d i a c e t y l e n e s i n g l e c r y s t a l f i b r e s have v e r y high v a l u e s of Young's modulus when account i s taken of the r e l a t i v e l y h i g h c r o s s - s e c t i o n a l a r e a of the m o l e c u l e s caused by the presence of r e l a t i v e l y l a r g e s i d e - g r o u p s . F o r example, each m o l e c u l e i n polyDCHD (24) s u p p o r t s an a r e a of about 1 nm compared w i t h the c r o s s - s e c t i o n a l a r e a of a p o l y e t h y l e n e m o l e c u l e (0.18 nm ). Hence polyDCHD has about the same p e r - c h a i n modulus as p o l y e t h y l e n e and b o t h have about the same v a l u e of diamond ( 2 7 ) . T h i s i n d i c a t e s the tremendous p o t e n t i a l t h a t polymer c r y s t a l s have as s t i f f and hence s t r o n g m a t e r i a l s ( 2 7 ) . Improvements i n the m o d u l i of p o l y d i a c e t y l e n e c r y s t a l s w i l l be gaXned by p r e p a r i n g good s i n g l e c r y s t a l s of new d e r i v a t i v e s w i t h s m a l l e r side-groups. 2

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Creep. One of the most r e m a r k a b l e a s p e c t s of the d e f o r m a t i o n of p o l y d i a c e t y l e n e s i s t h a t i t i s n o t p o s s i b l e t o measure any t i m e dependent d e f o r m a t i o n o r c r e e p when c r y s t a l s a r e deformed i n t e n s i o n p a r a l l e l t o the c h a i n d i r e c t i o n (14,24). This behviour i s demonstrated i n F i g u r e 3 f o r a polyDCHD c r y s t a l h e l d a t c o n s t a n t s t r e s s a t room temperature and the i n d i c a t i o n s a r e t h a t c r e e p does not take p l a c e a t temperatures of up t o a t l e a s t 100 °C ( 2 4 ) . Creep and time-dependent d e f o r m a t i o n a r e n o r m a l l y a s e r i o u s draw-back i n t h e use of c o n v e n t i o n a l high-modulus polymer f i b r e s such as p o l y e t h y l e n e s ( 2 8 ) . D e f e c t s such as l o o p s and c h a i n - e n d s a l l o w the t r a n s l a t i o n of m o l e c u l e s p a r a l l e l t o the c h a i n d i r e c t i o n i n p o l y e t h y l e n e f i b r e s . In c o n t r a s t s i n c e p o l y d i a c e t y l e n e s i n g l e c r y s t a l f i b r e s c o n t a i n p e r f e c t l y - a l i g n e d l o n g polymer m o l e c u l e s ( c f F i g u r e l b ) t h e r e i s no mechanism whereby c r e e p can t a k e p l a c e even at h i g h temperatures. F r a c t u r e . The most i n t e r e s t i n g a s p e c t of the f r a c t u r e b e h a v i o u r of p o l y d i a c e t y l e n e s i s the h i g h s t r e n g t h t h a t s i n g l e c r y s t a l f i b r e s can e x h i b i t when deformed p a r a l l e l t o the c h a i n d i r e c t i o n . I t i s found t h a t the f r a c t u r e s t r e n g t h of the f i b r e s d e c r e a s e s as the f i b r e d i a m e t e r i n c r e a s e s (14,24,25). I t has been shown (24,25) t h a t t h i s i s due t o the p r e s e n c e of s u r f a c e d e f e c t s on the f i b r e s and t h e ' t h e o r e t i c a l s t r e n g t h ( i . e . the s t r e n g h of a d e f e c t - f r e e c r y s t a l ) of polyDCHD f i b r e s has been shown (24) t o be 3±lGPa. T h i s c o r r e s p o n d s to a f o r c e r e q u i r e d t o b r e a k i n d i v i d u a l m o l e c u l e s of about 3 nN. K e l l y (29) has e s t i m a t e d the s t r e n g t h of a p o l y e t h y l e n e m o l e c u l e as 6 nN but t h i s i s now thought t o be r a t h e r h i g h ( 3 0 ) . Kausch (31) has shown t h a t a c o v a l e n t l y - b o n d e d m o l e c u l e s h o u l d be b r o k e n by a f o r c e o f the o r d e r of 3 n N - i d e n t i c a l to the v a l u e determined e x p e r i m e n t a l l y f o r polyDCHD. Hence i t can be seen t h a t these h i g h l e v e l s of s t r e n g t h measured f o r the p o l y d i a c e t y l e n e f i b r e s a r e c o n s i s t e n t w i t h the p r e d i c t i o n s of Frank (27) i n 1970. 1

Composites I t i s w e l l - e s t a b l i s h e d (32) t h a t composites produced by i n c o r p o r a t i n g high-modulus f i b r e s i n a b r i t t l e m a t r i x such as an epoxy r e s i n can have o u t s t a n d i n g m e c h a n i c a l p r o p e r t i e s . Recent examples have i n c l u d e d composites produced w i t h high-modulus p o l y e t h y l e n e f i b r e s (33) and a r o m a t i c polyamide f i b r e s ( 3 4 ) . P o l y d i a c e t y l e n e s i n g l e c r y s t a l f i b r e s a l s o o f f e r c o n s i d e r a b l e promise as r e i n f o r c i n g f i b r e s because they have h i g h s t i f f n e s s and s t r e n g t h , low c r e e p , good thermal s t a b i l i t y and low d e n s i t y ( 2 4 ) . Recent i n v e s t i g a t i o n s (35-37) i n t o the b e h a v i o u r of p o l y d i a c e t y l e n e s i n g l e c r y s t a l f i b r e s i n epoxy r e s i n m a t r i c e s have shown t h a t n o t o n l y do such composites have p r o m i s i n g m e c h a n i c a l p r o p e r t i e s b u t t h a t fundamental d e t a i l s of the mechanisms of f i b r e r e i n f o r c e m e n t can a l s o be r e v e a l e d f r o m t h e i r s tudy. Micromechanisms of r e i n f o r c e m e n t . I t was p o i n t e d out e a r l i e r t h a t the v i b r a t i o n a l f r e q u e n c i e s of c e r t a i n m a i n - c h a i n Raman a c t i v e modes a r e found t o change w i t h the l e v e l of a p p l i e d s t r a i n ( 2 6 ) . The b i g g e s t change i s found f o r the C=C t r i p l e bond s t r e t c h i n g f r e q u e n c y which i s of the o r d e r of 20 cm- /%. T h i s p r o p e r t y can be used t o determine the s t r a i n i n any p o l y d i a c e t y l e n e f i b r e s u b j e c t e d t o any 1


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Figure 3. Variation of s t r a i n with time for a poly DCHD f i b r e held at constant load.


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g e n e r a l s t a t e o f s t r e s s . The f i b r e s behave as though they have an i n t e r n a l m o l e c u l a r s t r a i n gauge and t h e Raman t e c h n i q u e has been r e c e n t l y employed t o m o n i t o r t h e p o i n t - t o - p o i n t v a r i a t i o n i n s t r a i n i n p o l y d i a c e t y l e n e f i b r e s i n epoxy composites (35,36) t o a h i g h degree o f a c c u r a c y and p r e c i s i o n . I t has proved p o s s i b l e t o measure the dependence o f c r i t i c a l l e n g t h s (32) o f i n d i v i d u a l f i b r e s a s a f u n c t i o n o f f i b r e diameter, confirming t h e o r e t i c a l p r e d i c t i o n s (32). In a d d i t i o n , i t i s a l s o p o s s i b l e t o f o l l o w i n t e r a c t i o n s between t h e f i b r e s and m a t r i x such a s f i b r e t w i n n i n g and k i n k i n g caused by r e s i n shrinkage (36). M e c h a n i c a l p r o p e r t i e s . Some p r e l i m i n a r y measurements have been made of t h e m e c h a n i c a l p r o p e r t i e s o f composites c o n s i s t i n g o f a l i g n e d polyDCHD s i n g l e c r y s t a l f i b r e s (- 10 mm l o n g ) i n an epoxy r e s i n m a t r i x ( 3 7 ) . F i g u r e 4 shows a s t r e s s / s t r a i n curve f o r a sample w i t h f i b r e volume f r a c t i o n , V f , o f 55.5%. The d e f o r m a t i o n i s l i n e a r up to t h e f r a c t u r e s t r a i n o f - 0.8% r e f l e c t i n g the l i n e a r i t y o f t h e s t r e s s / s t r a i n curves f o r i n d i v i d u a l f i b r e s a t l o w s t r a i n s ( F i g u r e 2 ) . I t i s found t h a t the m e c h a n i c a l p r o p e r t i e s o f polyDCHD/epoxy composites depend s t r o n g l y upon t h e f i b r e volume f r a c t i o n and t h i s i s demonstrated i n F i g u r e 5. I t can be seen t h a t t h e Young's modulus, E, o f t h e composite i n c r e a s e s as t h e volume f r a c t i o n o f f i b r e s i n c r e a s e s . The e x p e r i m e n t a l p o i n t s f a l l between t h e V o i g t ( u n i f o r m s t r a i n ) and Reuss ( u n i f o r m s t r e s s ) l i n e s ( 3 2 ) . F o r a u n i a x i a l l y a l i g n e d composite sample i t would be expected t h a t t h e d a t a s h o u l d f a l l c l o s e t o t h e V o i g t l i n e and i t i s thought (37) t h a t t h e s h o r t f a l l i n modulus i s due t o a c o m b i n a t i o n o f f i b r e m i s a l i g n m e n t and f i b r e - t w i n n i n g due t o r e s i n s h r i n k a g e . I t i s a l s o found t h a t t h e r e i s a g e n e r a l i n c r e a s e i n s t r e n g t h o f the composites w i t h i n c r e a s i n g f i b r e volume f r a c t i o n . However, a t low v a l u e s o f V f t h e s t r e n g t h i s below t h a t o f t h e pure r e s i n u n t i l s u f f i c i e n t f i b r e s a r e p r e s e n t t o produce r e i n f o r c e m e n t (29) and a t h i g h v a l u e s o f V f (> 60%) t h e s t r e n g t h f a l l s o f f because t h e r e i s not enough r e s i n t o wet t h e f i b r e s ( 3 7 ) . Conclusions I t has been demonstrated t h a t p o l y d i a c e t y l e n e s i n g l e c r y s t a l f i b r e s a r e r e l a t i v e l y p e r f e c t and have e x c e l l e n t m o l e c u l a r a l i g n m e n t . I n consequence they d i s p l a y h i g h v a l u e s o f s t i f f n e s s and s t r e n g t h and are very r e s i s t a n t t o creep. I t h a s been shown t h a t such f i b r e s have c o n s i d e r a b l e promise a s r e i n f o r c i n g f i b r e s i n an epoxy r e s i n m a t r i x and t h e study o f such composite systems has enabled c o n s i d e r a b l e fundamental i n f o r m a t i o n t o be o b t a i n e d c o n c e r n i n g the mechanisms o f f i b r e reinforcement.



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Figure 4. S t r e s s / s t r a i n curve for an aligned poly DCHD/epoxy composite.

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Acknovledgmen t s Most of the work described above was carried out at Queen Mary College, London and the author i s grateful to Professor D. Bloor and Dr. D. N. Batchelder f o r introducing him to polydiacetylenes and f o r their continued encouragement and help. He would also l i k e to thank Mr. D. Ando and Mr. I. F. Chalmers f o r their help i n the preparation of monomers. F i n a l l y , he must extend h i s gratitude to Dr. R. T. Read, Dr. C. G a l i o t i s , Dr. P. H. J . Yeung and Mr. I. M. Robinson who performed the bulk of the experimental work described above.


Literature Cited 1. Wegner, G. Pure Appl. Chem. 1977, 49, 443. 2. Bloor, D.; Chance, R. R. "Polydiacetylenes" (NATO ASI); Martinus Nijhoff Publishers: Dordrecht, Holland, 1985. 3. Bloor, D.; Koski, L.; Stevens, G. C.; Preston, F. H.; Ando, D.J. J. Mater. Sci. 1975, 10, 1678. 4. Yee, K. C.; Chance, R. R. J. Polym. Sci., Polym. Phys. Ed. 1978, 16, 431. 5. Young, R. J. "Introduction to Polymers"; Chapman and Hall: London, 1981. 6. Gell, P. H. "Polymer Single Crystals"; Interscience: New York, 1963. 7. Kelly, Α.; Groves, G. W. "Crystallography and Crystal Defects"; Longman: London, 1970; Chap. 11. 8. Young, R. J.; Bowden, P. B. J. Mater. Sci. 1973, 8, 1177. 9. Bowden, P. B.; Young, R. J. J. Mater. Sci. 1974, 9, 2034. 10. Allan, P.; Bevis, M. Proc. Roy. Soc. 1974, A34, 75. 11. Allan, P.; Crellin Ε. B.; Bevis, M. Phil. Mag. 1973, 27, 127. 12. Andrews, Ε. H.; Martin, G. E. J. Mater. Sci. 1973, 8, 1315. 13. Galiotis, C.; Young, R. J.; Ando, D. J.; Bloor, D. Makromol. Chem. 1983, 194, 1083. 14. Galiotis, C.; Young, R. J. Polymer 1983, 24, 1923. 15. Kobelt, D.; Paulus, E. F. Acta Cryst. 1974, B30, 232. 16. Hadicke, E.; Mez, H. C.; Krauch, C. H.; Wegner, G.; Kaiser, J. Angew. Chem. 1971, 83, 253. 17. Apgar, P. Α.; Yee, K. C. Acta Cryst. 1978, B34, 957. 18. Read, R. T.; Young, R. J. J. Mater. Sci. 1979, 14, 1968. 19. Read, R. T.; Young, R. J. J. Mater. Sci. 1984, 19, 327. 20. Read, R. T.; Young, R. J. J. Mater. Sci. Lett. 1981, 16, 2922. 21. Read, R. T.; Young, R. J. Phil. Mag. A. 1980, 42, 629. 22. Young, R. J.; Petermann, J. J. Polym. Sci., Polym. Phys. Ed. 1982, 20, 961. 23. Young, R. J.; Read, R. T.; Petermann, J. J. Mater. Sci. 1981, 16, 1835. 24. Galiotis, C.; Read, R. T.; Yeung, P. H. J.; Young, R. J.; Chalmers, I. F.; Bloor, D. J. Polym. Sci., Polym. Phys. Ed. 1984, 22, 1589. 25. Baughman, R. H.; Gleiter, H.; Sendfeld, N. J. Polym. Sci., Polym. Phys. Ed. 1975, 13, 1871. 26. Galiotis, C.; Young, R. J.; Batchelder, D. N. J. Polym. Sci., Polym. Phys. Ed. 1983, 21, 2483. 27. Frank, F. C. Proc. Roy. Soc. 1970, A319, 127. 28. Capaccio, G.; Gibson, G.; Ward, I. M. In "Ultra-High Modulus Polymers"; Eds. Ciferri, Α.; Ward, I. M.; Applied Science: London, 1979, p. 1. Sandman; Crystallographically Ordered Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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29. Kelly, A. "Strong Solids"; Clarendon Press: Oxford, 1966. 30. Kinloch, A. J.; Young, R. J. "Fracture Behaviour of Polymers"; Applied Science: London, 1983. 31. Kausch, H. H. "Polymer Fracture"; Springer-Verlag: Berlin, 1978. 32. Hull, D. "An Introduction to Composite Materials"; Cambridge University Press, 1981. 33. Ladizersky, Ν. H.; Ward, I. M. J. Mater. Sci. 1983, 18, 533, 34. Piggott, M. R.; Harris, B. J. Mater. Sci. 1980, 15, 2533. 35. Galiotis, C.; Young, R. J.; Yeung, P. H. J.; Batchleder, D. N. J. Mater. Sci. 1984, 19, 3640. 36. Robinson, I. M.; Yeung, P. H. J.; Galiotis, C.; Young, R. J.; Batchelder, D. N. J. Mater. Sci. submitted. 37. Galiotis, C.; Young, R. J.; Batchelder, D. N. to be published. July 26, 1986


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Relationship between Structure and Mechanical Properties of

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